6F - Team Buick
Contents
1. HOSE TVS TO HIGH VACUUM SOURCE ENERGY WHITE IGNITION V HOSE TVS TO HEI PURPLE 5 32 X 12 JS EGR EFE TOVACUUM TO Ie SWITCH HOSE CANISTER TO AIR CLEANER SOURCE C N HOSE TVS NN 9 HOSE TVS TO CARBURETOR Ww EGR VACUUM VACUUM FITTING ORANGE SOURCE WHITE 5 32 X 14 5 32 X 10 CHARCOAL TO CARBURETOR 1 CANISTER CARBURETOR EGR EFE SWITCH TVS SWITCH 99614 Figure 6F 25 231 Engine Vacuum Hose Routing less California TO SPARK HOSE EGR EFE SWITCH HOSE CARBURETOR TO DELAY VALVE TO VACUUM FITTING SPARK DELAY VALVE FROM YELLOW 5 32 X 16 ORANGE 5 32 X 3 AIR HOSE EGR EFE TO m E ERN HOSE EGR EFE swircH CLEANER YELLOW E G R TO EFE PIPE GREEN FROM VALVE 5 32 X 7 WIRING NS AIR ime HARNESS HOSE EGR EFE b CLEANE CLIP EGR PINK VIEW OF CARBURETOR WIRING YU HARNESS EGR EFE SECTION A A T HOSE TVS TO HOSE EGR EFE SWITCH ENERGY KA CHEM SOURCE TO EGR PINK 7 32 X 22 IGNITION WHITE HOSE TVS TO HEI PURPLE EGR 32X12 EFE SWITCH e HOSE CANISTER TO AIR CLEANER VACUUM TO SOURCE HEI SPARK HOSE TVS TO DELAY VACUUM FITTING VALVE HOSE TVS TO SPARK TO WHITE 5 32 X 14 DELAY VALVE EGR ORANGE 5 32 X 3 HOSE CARBURETOR TO SPARK EGR EFE SWITCH CANIS ER CARBURETOR DELAY VALVE VACUUM BLUE2. SYSTEMS 6F 9 le o n T n n M Part throttle engine 1 Insufficient exhaust 1 Check EGR valve hose routing detonation gas recirculation flow Check EGR valve operation Repair during part throttle or replace as required Check accelerations EGR thermal vacuum switch as listed under Engine Idles Ab normally Rough and or Stalls Replace switch as required Check EGR passages and valve for ex cessive deposits Clean as required NOTE Detonation can be caused by several other engine variables Perform ignition and carburetor related diagnosis Engine starts but imme 1 EGR valve hoses 1 Check EGR valve hose routings eiately stalls when misrouted cold Cans 2 EGR system malfunc 1 Perform check to determine if tioning when engine is EFE EGR thermal vacuum switch cold is operational Replace as required NOTE Stalls after start can also be caused by carburetor problems Refer to carburetor diagnosis section EFE EGR VACUUM SWITCH 231 350 455 ENGINES AND 260 ENGINE CALIFORNIA ONLY Condition Possible Causes Correction Rough idle or stall 1 No vacuum to EFE 1 Check vacuum source for vacuum during warm up vacuum actuator with en of 8 hg or above gine coolant temperature below 120 3 F 2 Correct improper vacuum hose routing
3. 6F 15 Removal and Installation A I R System Units 6F 16 Removing and Installing EGR Valve 6F 16 Removal and Installation of Catalytic Converter 1 6F 16 Catalytic Converter Bottom Cover Replacement 6F 17 Removal and Replacement of EFE EGR Switch 2200 20 6F 19 SPECIFICATIONS Emission Control System Specifications 6F 19 Engine Hardware Usage Chart 6F 20 1 6F 2 1975 BUICK SERVICE DESCRIPTION AND CLOSED POSITIVE CRANKCASE VENTILATOR SYSTEM All cars have a closed Positive Crankcase Ventilating Sys tem to provide more complete scavenging of crankcase vapors Ventilation air 15 drawn through a filter assembly located in the air cleaner through a hose into the left rocker arm cover down into the crankcase across and up into the rear of the intake manifold up through the ven tilator valve through a hose and into the intake manifold Intake manifold vacuum draws any fumes from the crank case to be burned in the engine When air flow through the carburetor is high added air from the Positive Crankcase Ventilating System has no noticeable effect on engine operation however at idle speed air flow through the carburetor is so low that any large amount added by the ventila
4. TO CHECK E F E VALVE FOR PROPER OPERATION 1 Visually inspect manifold heat valve for damaged valve or linkage disconnected linkage and cracked or deteriorated vacuum line 2 Apply at least 10 inches of vacuum from an external vacuum source to EFE vacuum diaphragm 3 Valve should move freely Vacuum diaphragm must hold plunger in retracted position for one minute without applying additional vacuum TO CHECK E F E SOLENOID FOR PROPER OPERATION Visually inspect hoses wires and fuses for proper connec tions cracking abrasion pinching or deterioration Re pair or replace as necessary 1 Connect a vacuum gage to the hose at the EFE valve actuator 2 Disconnect the lead from the engine oil temperature switch With the engine running ground the lead to the engine The vacuum gage should indicate idle vacuum If idle vacuum is indicated go to Step 3 If idle vacuum is not indicated go to Step 2a 2a Stop engine and then turn ignition switch to the Run position Using a voltmeter check for battery volt age at the solenoid tan wire If battery voltage is not indicated check the power circuit and repair as necessary If battery voltage is indicated check the continuity of the ground circuit with an ohmmeter and repair if necessary If the ground circuit is good replace the solenoid 3 With the engine running and the engine oil at normal operating temperature disconnect the temperature switch lead from gr
5. www systems EMISSION CONTROL SYSTEMS ALL SERIES CONTENTS DESCRIPTION AND OPERATION All Engines Positive Crankcase Ventilation System PCV ccssscsssssssessecsesssecsucssecsssssssesssecsssessecesssscssece 6F 2 Thermostatically Controlled Air Cleaner eres 6F 2 Air Injection Reactor System A LR scesssessssssssssssssesssessssessecssecssessessuecssessssessssssuccescsssecesnecens 6F 3 Catalytic eei ches atl S UR e E ERES 6F 3 Choke Air Modulator System 231 350 and 455 Engines ONY a hende 6F 3 Exhaust Gas Recirculation System EGR sce 6F 3 Early Fuel Evaporation System EFE 6 6F 4 Evaporative Emission System scssssssssssssssssssssesssssessussessucsssecssuessssesuscsssesssescssscssssecsusecssusecsuse 6F 4 231 Engine Distributor Vacuum Advance Delay 6F 4 400 Engine Distributor Vacuum Spark Retard Delay Valve sees 6F 4 DIAGNOSIS All Engines Positive Crankcase Ventilation System PCV 6F 4 Thermostatically Controlled Air Cleaner 6F 5 Air Injection Reactor System 000 6F 5 Catalytic Converter i 6F 6 Choke Air Modulator Syste
6. Check vacuum signal into switch thermal vacuum switch from carburetor EGR port with engine at normal operating tempera ture and at curb idle speed Then check vacuum signal out of switch to EGR valve If the two vac uum signals are not equal with 1 2 in hg them proceed to EFE EGR thermal vacuum switch diagnosis Replace switch as required 6 EGR valve gasket 1 Check EGR attaching bolts for failed or loose EGR tightness Tighten as required If attaching bolts not loose remove EGR valve and inspect gasket Replace as re quired MM M 1 EGR valve vacuum 1 Check EGR valve vacuum hose hose misrouted routing Correct as required 2 Failed EFE EGR 1 Same as Step 5 above under thermal vacuum switch Engine Idles Abnormally Rough and or stalls 3 EGR flow unbalanced 1 Clean EGR passages of all due to deposit accumula deposits tion in EGR passages or under carburetor 4 Sticky or binding 1 Remove EGR valve and inspect EGR valve for proper operation Clean or re pair as required Engine stalls on decelerations 1 Restriction in EGR 1 Check EGR vacuum lines for vacuum line kinks bends etc Remove or re place hoses as required Check EGR thermal vacuum switch for excessive restriction Replace as required Check EGR valve for excessive de posits causing sticky or binding operation Clean or repair as required www
7. leak in connecting sys tem or EFE vacuum actuator di aphragm Replace 3 Failed EFE EGR thermo vacuum switch Replace 2 Vacuum to EGR valve 1 Correct improper vacuum hose below 120 3 F routing if necessary 2 Failed EFE EGR thermo vacuum switch Replace Rough idle lack of 1 Vacuum to EFE I Correct improper vacuum hose performance surge uum actuator with engine routing after warm up period coolant temperature above 120 F 3 F 2 Failed EFE EGR thermo vacuum switch Replace Improper EGR operation 1 Vacuum to EGR valve 1 Correct improper vacuum hose with engine coolant routing if necessary temperature below 120 F 3 F 2 Failed EFE EGR thermo vacuum switch Replace ee eee ee 6 10 1975 BUICK SERVICE MANUAY SYSTEM 231 350 455 5 Condition Possible Cause Correction Poor Operation during 1 No vacuum to vacuum 1 Check vacuum source for vacuum warm up such as rough actuator during warm up of 8 hg or above idle stumble etc period for cold start Repair improper vacuum hose rout ing leak in connecting system dia phragm or EFE EGR TVS Failed EFE EGR TVS Replace 2 EFE valve linkage 1 Repair EFE valve linkage bent or binding 3 EFE valve linkage 1 Reconnect linkage disconnected 4 EFE valve shaft 1 Replace EFE valve frozen in bearing 5 EFE valve loose 1
8. 1 E G VALVE BACK PRESSURE VALVE TO BACK PRESSURE TRANSDUCER VALVE 05 PRESSURE TRANSDUCER VALVE CONTROL VALVE HOSE VACUUM PIPE T V TRANSDUCER VALVE CARBURETOR VALVE 6 R CONTROL COVER E R CONTROL VALVE ASM TO VALVE INTAKE MANIFOLD ASM VACUUM CHECK HOSE CONTROL VALVE ASM TO T V 5 TE HOSE T V S TO CHECK VALVE HOSE MODULATOR PIPE TO TEE MODULATOR PIPE VALVE ASM VACUUM CHECK HOSE T V S amp EGR T V S TO CHECK VALVE 6F18 Figure 6F 29 260 Engine Vacuum Hose Routing California 6F17 Figure 6F 30 260 Engine EFE Valve 28 1975 BUICK SERVICE PRESSURE STRAP MUST BE POSITIONED JUST FORWARD OF VENT FILTER AS SHOWN E G R HOSE ROUTING CALIFORNIA 5B6F18 Figure 6F 31 260 Engine EGR Valve Strap HOSE EGR EFE SWITCH TO EFE HOSE EGR EFE SWITCH EE HOSE TVSTO GREEN HARNESS ASSEMBLY TO CARBURETOR BLUE TEE YELLOW SWITCH TO TEE VACUUM HOSE EGR ORANGE TAPE HOSE MANIFOLD YELLOW HOSE PART TOTEE OF AIR CLEANER HOSE PART OF D CLEANER STA STRAP EGR EFE SWITCH OSE CARBURETOR O CANISTER HOSE TVS TO HEI PURPLE HOSE EGR EFE TO EGR PINK HIGH ENERGY IGNITION HARNESS M ROUTE HOSE UNDER VACUUM
9. 7 32 X 8 5 SOURCE EGR EGE SWITCH TVS SWITCH 5BGF15 Figure 6F 26 231 Engine Vacuum Hose Routing California Ww TeamBuick com 6F 26 1975 BUICK SERVICE EXHAUST MANIFOLD LEFT 277 SJA PIPE EFE E HOSE VALVE amp ACTUATOR E F E 1 1 VACUUM PIPE EFE VACUUM CLIP EFE EGR SWITCH CLYLINDER HEAD VALVE amp THERMAL Be DATUR SWITCH VIEW A MCN 5B6F16 Figure 6F 27 231 Engine EFE Valve E F E ACTUATOR F PIPE EF E VACUUM ACTUATOR TO PIPE HOSE PIPETO T V S HOSE T V S TO CHECK VALVE HOSE E G R VALVE TO BACK PRESSURE TRANSDUCER VALVE HOSE BACK PRESSURE TRANSDUCER VALVE TO CONTROL VALVE BACK PRESSURE E G R VALVE INTAKE MANIFOLD VACUUM CONNECTOR EFE T V S TRANSDUCER VALVE HOSE CONNECTOR TO INTAKE MANIFOLD VALVE ASM CHECK CARBURETOR VALVE ASM E G R CONTROL DISTRIBUTOR CONNECTOR VACUUM COVER CONTROL VALVE HOSE VACUUM DELAY VALVE HOSE CHECK VALVE TO CONNECTOR HOSE HOSE CONTROL VALVE TO CARB MODULATOR TO CONNECTOR HOSE DISTRIBUTOR TO VACUUM DELAY VALVE 5B6F17 Figure 6F 28 260 Engine Vacuum Hose Routing less California www 2 SYSTEMS 6F 27 ACTUATOR VACUUM ACTUATOR TO VACUUM PIPE
10. Replace EFE valve on shaft CLOSED EFE VALVE Condition Possible Cause Correction Poor Operation after 1 Failed EFE EGR TVS 1 Replace EFE EGR TVS warm up rough idle vacuum present at vacuum lack of high speed per actuator formance surge misses at all speeds 2 EFE valve asm shaft 1 Replace EFE valve frozen in bearing 3 EFE valve to housing 1 Repair EFE valve interference 4 Vacuum actuator link 1 Repair EFE valve linkage age bent or binding 5 EFE valve separated 1 Repair EFE valve linkage from shaft Noisy EFE valve asm 1 Linkage stop failed 1 Repair linkage stop tab 2 No vacuum actuator 1 Replace vacuum actuator linkage over travel 3 Valve loose on shaft 1 Replace EFE valve 4 Shaft loose in bushing 1 Replace EFE valve or bushing loose in housing DISTRIBUTOR VACUUM ADVANGE SPARIC A 11 D BRUSSTON CONTROL SYSTEMS DELAY 231 ENGINE CALIF ONLY 1 Connect a vacuum gauge to the T V S side of the valve and the Hand Operated Vacuum Pump with a vacuum gauge to the carburetor side of the valve 2 Draw a vacuum there should be a slight hesitation on the gauge reading at the T V S side The Hand Ope rated vacuum pump gauge should drop slightly and bal ance with the gauge reading at the T V S side This should take 3 to 4 seconds to balance the readings 3 If there is not a slight hesitation in readings the valve should be replaced 4 Remove the g
11. Vacuum Motor l Drill center of two spot welds using a 1 16 inch drill Do not center punch 2 Enlarge two holes using a 5 32 inch drill Use extreme care not to damage the air cleaner snorkel 3 Remove vacuum motor retainer strap See Figure 6F 3 INSTALL REPLACEMENTA SENSOR ASSM IN SAME POSITION AS ORIGINAL ASSM 6F 4 D 2 RETAINING STRAP Figure 6F 3 Replacing Vacuum Motor Assembly 4 Lift vacuum motor cocking it to one side to unhook motor linkage at the control door 5 Drill a 7 64 hole in snorkel tube at point as shown in Figure 6F 3 6 Use the motor strap retainer and the sheet metal screw provided in the motor service package to secure the re tainer and motor to the snorkel tube 7 Make sure the screw does not interfere with the operat ion of the damper assembly Shorten screw if required 6F 15 R and R Air Cleaner Sensor 1 Remove two sensor retaining clips by prying See Figure 6F 4 SENSOR RETAINING CLIP as IT Figure 6F 4 Replacing Sensor Assembly 2 Pull vacuum hoses from sensor 3 Note carefully the installed position of the sensor so that you can install new sensor in same position Then remove sensor 4 Install sensor and gasket assembly in air cleaner in same position as noted in Step 3 This is to eliminate the possi bility of interference with the air filter element See Figure 6 4 5 Install sensor retaining clip Meanwhile supporti
12. acceleration BACK PRESSURE TRANSDUCER VALVE BPV 260 CU IN ENGINE Some V 8 engines use the BPV with the EGR valve to modulate Exhaust Gas Recirculation to engine load Exhaust pressure in the exhaust pressure prove of the BPV moves a diaphragm against spring pressure to seal the air bleed when engine load is high allowing maximum EGR When engine load decreases exhause pressure decreases in the exhaust pressure probe The spring then pushes the diaphragm down Vacuum to the EGR valve is than bled through the air bleed reducing vacuum to the EGR valve and Exhaust Gas Recirculation EGR vacuum is ported to assure no EGR at idle and wide open throttle conditions Functional Check BPV 1 Remove air cleaner assembly and plug manifold vacuum fitting 2 With A C drive wheels blocked transmission in park start engine and bring to operating temperature Put cam follower on high step of fast idle cam 3 Check vacuum on source control valve side of BPV valve record reading 4 T a vacuum gauge to the EGR control valve side of BPV valve Vacuum should be 1 7 to 2 7 HG Replace BPV valve is not within specifications Leave vacuum gauge at this location Remove hose from EGR valve and plug hose Read vacuum gauge should be the same as source vacuum Step 3 If not within 2 inches of source vacuum replace BPV valve 5 Remove vacuum gauge and install air cleaner assem bly 6 12 1975 SER
13. channels at each end of the converter See Figure 6F 16 Figure 6F 12 Insulation Removed CONVERTOR COVER Figure 6F 10 Cutting Off Bottom Cover CONVERTER M BOTTOM COVER Figure 6F 11 Cutting Off Bottom Cover Figure 6F 14 Installing Replacement Cover CONTROL SYSTEMS 19 Figure 6F 15 Installing Retaining Channels Figure 6F 16 Retaining Channel Clamps Installed 2 Top plastic part of switch may have to be indexed to EGR EFE Thermal Vacuum Switch Removal and line up with a wrench flat of metal part of switch Using Replacement a suitable size wrench turn top plastic part of switch so 1 as Tool J 25254 2 set down over top part of switch 231 260 350 400 455 Engines and turn lower metal part of switch Removal Repl t 1 Disconnect all vacuum hoses from switch NOTE This cannot used all metal switch 1 Reverse removal procedure SPECIFICATIONS EMISSION CONTROL SYSTEM SPECIFICATIONS Positive Crankcase Ventilator Valve Type 231 s nee CV768C 250 Reden CV781C QO 679 435 a Museau MAD Ot dogs CV768C PCV Valve Location ee Intake Manifold Carburetor Inlet Air Regulated Temperature 115 20 Air Injection Pump Be
14. engine Power take off for the pump is at the water pump pulley Intake air passes through a centrifugal fan at the front of the pump where foreign materials are separated from the air by centrifugal force Air is delivered to the intake manifold galleries by a formed flexible hose of 3 4 inside diameter fitted to a 3 4 exhaust tube on the div erter valve at the back of the pump The only serviceable component of the pump is the cen trifugal filter fan Do not assume pump is malfunctioning if it squeaks when turned by hand Do not lubricate the pump in any way If engine or underhood compartment is to be cleaned with steam or high pressure detergent the centrifugal filter fan should be masked off to prevent liquids from entering the pump Do not attempt to operate vehicle with the drive belt disconnected Diverter Valve and Silencer Assembly The diverter valve is attached to the back of the pump It senses manifold vacuum through a 3 16 fitting at the carburetor During sudden deceleration vacuum in creases cause the valve to open allowing air from the air injection pump to pass through the valve and silencer to the atmosphere Approximate duration of the valve opening is five seconds This valve also controls pressure within the system by diverting excessive pump output to the atmosphere through an internal muffler Check Valve The check valve has a one way diaphragm which prevents hot exhaust gases from backing up
15. of operat ion until the outer diameter sealing lip has worn in DIVERTER VALVE Removal 1 Remove hoses on valve 2 Remove two screws holding valve to pump and remove valve 3 Remove gasket material from valve and pump Installation 1 Do not use a gasket when replacing the diverter valve 2 Install valve and secure with two screws Torque to 120 160 Ib in 3 Connect hoses to valve assembly CHECK VALVE Removal 1 Release clamp and disconnect air hose from check valve 2 Unscrew check valve 1 Reinstall check valve 2 Install air hose to check valve INJECTION TUBES REPLACEMENT L6 only There is no periodic service or inspection for the air injec tion tubes yet whenever the cylinder head is removed inspect the air injection tubes for carbon build up and warped or burned tubes Remove any carbon build up with a wire brush Warped or burned tubes must be replaced Replacement On in line engines remove carbon from tubes and using penetrating oil work tubes out of cylinder head E G R VALVE REMOVAL AND INSTALLATION Removal 1 Disconnect vacuum hose from valve 2 Remove bolt or bolts holding valve to manifold and remove valve Installation 1 Install gasket and valve in manifold and tighten bolts 2 Connect vacuum hose to valve CATALYTIC CONVERTER Catalyst Removal and Replacement Removal If necessary the catalyst in the converter can be replaced on the car with Tool J 25
16. position 1 Thermac damper door 1 Perform diagnostic tests on thermac system as described M TESTING THERMO AIR CLEANER OPERATION Since failure of the thermo air cleaner will generally result in the damper door staying in the full open snorkel posi tion failure will probably go unnoticed in warm or hot weather In cold weather however owners will complain of leaness hesitation sag surge or stalling When any type of lean operation complaint is received always test the thermo air cleaner for proper functioning before doing any work on the carburetor Always perform checks in the same order as listed below Vacuum Motor Check 1 Check all hoses for proper hook up Check for kinked plugged or damaged hoses 2 With the engine OFF observe damper door position through snorkel opening If position of snorkel makes observation difficult use the aid of a mirror At this point damper door should be in such a position that the heat Stove passage is covered snorkel passage open If not check for binds in linkage 3 Apply at least 7 in Hg of vacuum to the diaphragm assembly through hose disconnected at sensor unit Damper door should completely close snorkel passage when vacuum is applied If not check to see if linkage is hooked up correctly and for a vacuum leak 4 With vacuum applied bend or clamp hose to trap vacuum in diaphragm assembly Damper door sho
17. stops flowing disconnect air supply to the vibrator 6 Remove vibrator and check that catalyst has filled converter flush with fill plug hole Add catalyst if re quired 7 Apply an anti seize compound to the fill plug install and tighten to 50 Ib ft 8 Disconnect air supply to aspirator and remove 2 FILL TUBE EXTENSION INSTALLED 5 6 5 Figure 6F 9 Fill Tube Extension Installed Catalytic Converter Bottom Cover Replacement If for any reason the bottom cover of the converter is torn or severely damaged it can be replaced with a repair kit 1 Remove bottom cover by cutting close to the bottom outside edge See Figures 6F 10 and 6F 11 Do not remove the fill plug The depth of the cut must be very shallow to prevent damage to the inner shell of the converter 2 Remove insulation See Figure 6F 12 3 Inspect inner shell of the converter for damage If there is damage in the inner shell the converter assembly must be replaced 4 Place new insulation in the replacement cover Apply sealing compound all around the cover after the insula tion is in position Apply extra sealer at the front and rear opening for the pipes See Figure 6F 13 nme 6F 18 1975 BUICK SERVICE MANUAL 5 Install replacement cover converter Figure 6 14 6 Install cover retaining channels both sides of the converter See Figure 6F 15 7 Attach 2 clamps over retaining
18. 077 NOTE Separate hoses should be attached to the aspira tor and the vibrator with maximum available pressure Minimum of 60 psi in each hose If the car has dual tailpipes attach the aspirator to one pipe and place a plug in the other pipe 1 Install aspirator See Figure 6F 6 2 Connect air supply line to aspirator to create a vacuum in the converter to hold beads in place when fill plug is removed 3 Remove converter fill plug with 3 4 hex wrench See Figure 6F 7 4 Clamp on vibrator See Figure 6 8 3 Install empty catalyst container to vibrator do not install fill tube extension at this time See Figure 6F 8 6 Disconnect air supply to aspirator and connect air supply to vibrator Catalyst will now drain from the con verter into the empty container 7 When all the catalyst has been removed from the converter disconnect air supply to vibrator and remove container from the converter 8 Discard used catalyst ASPIRATOR CATALYST CONTAINER WITH FILL TUBE EXTENSION E REMOVED Figure 6F 8 Clamping on Vibrator and Empty Catalyst Container WWW CONTROL SYSTEMS 6 17 Replacement 1 Fill container with approved replacement catalyst 2 Install fill tube extension to the fixture See Figure 6F 9 3 Connect air supply to aspirator and vibrator 4 Attach catalyst container to the fixture 5 After the catalyst
19. 2 Plugged vacuum source 3 Vacuum hose off pinched or plugged or a T connector cracked or broken Do not loose advance when removing hose at idle vance unit Damaged distributor ad 1 Replace part 2 Correct or replace part 3 Check hoses connectors and routing and correct Replace part No retard delay retard delay valve 2 Malfunctioning TVV in manifold 1 Malfunctioning spark 1 Replace part 2 Replace part 6 14 1975 BUICK SERVICE SYSTEM 250 Functional Test for Vacuum Advance Systems Full Vacuum Advance Systems 400 Cu In Engine California 1 Warm up engine to normal operating temperature 2 Hook up a timing light and observe for vacuum ad vance Timing should be advanced beyond the initial setting 3 Remove vacuum hose from distributor and observe for loss of vacuum advance Engine should return to specified initial timing setting 4 On engines equipped with a spark retard delay valve a Verify correct installation Side marked DIST should be connected toward the distributor Correct if needed b Locate hose connected to port marked 1 on TVV in manifold water crossover Remove hose from vacuum source Plug hose and cap the vacuum source c T a vacuum gauge into hose between distributor and the spark retard delay valve Place gauge so it can be observed from the driver s seat d Tu
20. HOSE 6 CONDITIONING HOSE TysTo BLUE BRACE WHEN AIR CARBURETOR CHARCOAL CONDITIONING IS ORANGE INDICATED CANISTER 5B6F21 Figure 6F 32 350 2 Bbl Engine Vacuum Hose Routing www l eamBulcK contor systems HOSE EGR EFE SWITCH TO TEE YELLOW HOSE CARBURETOR PART OF AIR CLEANER 6F 29 AIR CLEANER TO TEE SWITCH HOSE EGR EFE SWITCH TO EFE GREEN T HOSE CARBURETOR U TO CANISTER STA STRAP HIGH ENERGY IGNITION 1 4 gt du a P E 2 Y HARNESS VACUUM TEE TVS HOSE EGR EFE SWITCH TO EGR SWITCH PINK ROUTE HOSE UNDER AIR CONDITIONING HOSE TVS TO BRACE WHEN AIR TEE YELLOW CONDITIONING IS INDICATED HOSE EGR EFE SWITCH TO CARBURETOR BLUE HOSE TVS TO CARBURETOR ORANGE HOSE TVS TO HEI PURPLE HARNESS VACUUM HOSE TVS BLUE TAPE CHARCOAL CANISTER Figure 6F 33 350 4 Engine Vacuum Hose Routing less 1 HOSE PART OF HOSE PART OF AIR CLEANER AIR CLEANER pm EGR N TVS TO CARBURETOR SWITCH BLUE HOSE EGR SWITCH TO EGR PINK ROUTE HOSES UNDER CONNECTOR AIR CONDITIONING BRACE WHEN AIR CONDITIONING IS HOSE TVS TO INDICATED HOSE CARBURETOR CONNECTOR TO CONNECTOR YELLOW HARNESS ASSEMBLY VACUUM HOSE EGR YELLOW TAPE STA STRAP HOSE EF E EGR ORANGE TAPE T 5B6F22 HOSE CONNECTOR
21. I R 4 350 4BBL A AND B SERIES CALIFORNIA ONLY 5 455 4BBL B SERIES SEDAN AND COUPE CALIFORNIA ONLY FOR START OF PRODUCTION AND ALL SERIES AFTER START OF PRODUCTION 6 ALL 350 4BBL B SEDANS AND COUPES FOR CALIFORNIA ALL A WAGONS AND ALL SEDANS WITH A 3 23 REAR AXLE WILL HAVE TAIL PIPE DIFFUSERS 7 ALL 350 4BBL A WAGON FOR CALIFORNIA AND ALL 350 4BBL SEDANS AND COUPES FOR CALIFORNIA 8 NON CALIFORNIA ONLY 5B6F30 Figure 6F 17A Engine Hardware Usage Chart www conTROL svsrEMs 21 MANUAL TRANSMISSION VACUUM MOD HOSE FITTING M38 amp K89 350 AUTOMATIC TRANSMISSION 6F6 Figure 6F 17 250 Engine Vacuum Fittings less A C FITTING E F E HOSE AIR MANUAL TRANSMISSION CONDITIONING HOSE 90 3 CRANK VACUUM fff i MOD HOSE FITTING IN AIR CONDITIONING HOSE HOSE 350 AUTOMATIC TRANSMISSION 6F7 Figure 6F 18 250 Engine Vacuum Fittings with A C 6 22 1975 BUICK service MANUAL eamBuick com ATTACHING PARTS SHIELD HEAT FITTING SHIELD HEAT HOSE VACUUM FITTING HOSE CARBURETOR FRONT OF CAR 6F8 Figure 6F 19 250 Engine Switch and Shield AIR CLEANER GASKET COLORED ADHESIVE SURFACE TO CARBURETOR STUD CARBURETOR 6F9 Figure 6F 20 250 Engine Air Cleaner www eamBuick contro sy
22. N SYSTEM Condition Possible Cause Correction Fuel Odor 1 Vapor leak from evap l Inspect and correct as neces System sary fuel and evaporation hoses and pipes fuel sender sealing gasket and fuel cap M M EGR SYSTEM 231 350 455 ENGINES r U U f Condition Possible Cause Correction eee Engine idles abnormally 1 EGR valve vacuum 1 Check EGR valve vacuum hose rough and or stalls hoses misrouted routing Correct as required MM M 2 Leaking EGR valve 1 Check EGR valve for cect operation 3 Idle speed mis 1 Set idle RPM per engine label adjusted specification Remove EGR vacuum hose from valve and ob serve effect on engine Replace valve if speed is affected reset RPM to specification and re connect hose 6F 8 1975 BUICK SERVICE Engine runs rough on light throttle accel eration poor part load performance and poor fuel economy 4 Improper carburetor 1 Check vacuum signal from carbu signal to EGR valve retor EGR port with engine at at idle stabilized operating temperature and at curb idle speed If signal is more than 2 0 in hg vacuum proceed to carburetor idle diagnosis 5 Failed EFE EGR 1
23. TION SYSTEM EFE An early fuel evaporation valve EFE has been added to the exhaust system on most cars for 1975 the EFEvalve promotes quick heating of the incoming fuel by directing exhaust gas flow through the intake manifold crossover passage directly beneath the carburetor whenever engine coolant temperatures are below a specified temperature The EFE valve operation is the same for all engines how ever temperature control and methods of sensing temper ature are different and are covered in the Diagnosis Section DISTRIBUTOR VACUUM ADVANCE SPARK DELAY SYSTEM 231 CU IN ENGINE The distributor vacuum advance spark delay valve is used DIAGNOSIS PCV SYSTEM between the T V S and the carburetor ported spark port on early production models On after jobs the T V S switch is discontinued and the delay valve is located be tween the carburetor ported spark port and the distributor vacuum advance unit Ported spark to the distributor is metered through an orifice in the delay valve anytime distributor ported vacuum has been dropped to zero it will then take about 25 seconds to reach full vacuum advance DISTRIBUTOR VACUUM ADVANCE RETARD DELAY VALVE 400 CU IN ENGINE 1 Four second retard delay cold a These engines contain a parallel system of hose plumb ing in which one branch contains a spark retard delay valve and the other branch a thermal vacuum valve sens ing engine coolant temperature b At cold engine c
24. TO AIR PUMP iy 5a lt HOSE CARBURETOR 6 TOCANISTER MA HIGH ENERGY IGNITION EGR 1 SWITCH HOSE TVS TO lt CARBURETOR ORANGE HARNESS ASSEMBLY VACUUM HOSE TVS CHARCOAL BLUE TAPE CANISTER Figure 6F 34 350 4 Engine with A I R less EFE Valve 5B6F24 1975 BUICK service MANOA T eamBuick com TO ERE EGR SWITCH p CRUISE CONTROL CYLINDER HEAD POWER UNIT EXHAUST MANIFOLD 455 ENGINE LEFT PIPE BOLT FFE 10 20 LB FT SA PIPE N i Z EFE EAN HOSE ROCKER COVER VALVE amp ACTUATOR CRUISE CONTROL EFE RETAINER POWER UNIT VIEW 350 SHOWN Figure 6F 35 350 and 455 Engines EFE Valve ADJUSTING WASHER lt WASHER BRACKET STEERING amp PUMP MOUNTING 5B6F26 Figure 6 36 350 Engine 1 Pump Mounting www SYSTEMS 6F 31 TVS TO HOSE PART CARBURETOR F AIR CLEANER F AIR CLEANER ORANGE GREEN HOSE CARBURETOR TVS TO CANISTER YELLOW SWITCH ti HARNESS VACUUM T U STA STRAP HOSE TVS WHITE HIGH ENERGY IGNITION N HOSE EGR EFE SWITCH TO CARBURETOR E TOAIR BLUE CLEANER HOSE EGR EFE HE ua TO EGR EGR EFE SWITCH is lt lt
25. VICE WAN T ea MPAG K G to hose connected to lower EGR THERMAL CONTROL VALVE EGR TCV 260 CU IN ENGINE All 260 engines use a temperature sensitive control valve in the vacuum line to the EGR valve The valve is closed below 61 temperature blocking vacuum to the EGR valve giving better driveaway when the engine is cold The EGR control valve is open above 76 engine tempera ture allowing EGR ported vacuum to be directed to the EGR valve If vacuum is present at EGR valve below 61 F or no vacuum is present above 76 F valve must be replaced EGR CHECK VALVE EGR CV 260 CU CALIFORNIA ONLY check valve is used in the vacuum line from the carbu retor ported spark port to 1 port of the EFE EGR TVS switch The valve holds the highest ported vacuum reached to keep the E G R valve open during hard acceleration Note The back pressure transducer valve B P V bleed valve is closed during hard acceleration During deceleration or light engine loads the vacuum 15 modulated through the B P V reducing vacuum to the E G R valve thus reducing exhaust gas recirculation EXHAUST GAS RECIRCULATION SYSTEM EGR 400 CU IN ENGINE Function test the EGR valve as outlined under Checking EGR Valve Operation All Engines Functional Test of EGR Thermal VAcuum Valve 400 Cu In Engine 1 Valve is closed below 70 F and open above 70 2 Warm check above 70 F valve left on engine Fun
26. aner on engine and continue to step 2 below 2 Start and idle engine Damper door should move to close the snorkel passage immediately if engine is cool enough When damper door starts to open the snorkel passage in a few minutes remove air cleaner cover and read temperature gage It must read 115 degrees plus or minus 20 degrees 3 If the damper door does not start to open up the snorkel passage at temperature indicated temperature sensor is malfunctioning and must be replaced rn M Condition Possible Cause Correction M M Excessive Belt Noise 1 Loose belt Tighten belt 2 Seized pump 1 Replace pump 6 6 1975 BUICK SERVICE MANUAL eamBuick com Excessive Pump Noise 1 Leak in hose 1 Locate source of leak and Chirping Rumbling Or correct Knocking 2 Loose hose i 1 Reassemble and replace or tighten hose clamp 3 Hose touching other 1 Adjust hose position engine parts 4 Malfunctioning diver 1 Replace valve ter valve 5 Malfunctioning check 1 Replace valve valve 6 Pump mounting fasten 1 Re torque all mounting screws ers loose 7 Centrifugal filter fan 1 Replace centrifugal filter fan damaged 8 Malfunctioning pump 1 Replace pump No Air Supply 1 Loose belt 1 Tighten belt 2 Leak in 1 Locate source of leak and correct 3 Leak at hose fit
27. auge hose from the T V S side of the valve Cover the port with a finger draw a vacuum 5 The hand operated vacuum gauge pump reading should hold steady If the vacuum reading should show a leak replace the valve 5 Remove the finger and the gauge reading should drop slowly if the reading drops quickly to zero replace the valve EARLY FUEL EVAPORATION SYSTEM EFE 260 CU IN ENGINE Operation At engine temperatures less than the switching tempera ture of the TVS switch manifold vacuum is directed to the EFE actuator which closes the EFE heat valve and in creases the exhaust flow through the intake manifold crossover The added heat from the exhause gas improves cold start performance The valve starts to close at 5 7 of vacuum and is fully closed by 10 to 12 of vacuum Above the temperature of temperature of the controlling valve switching point the EFE valve remains open since no vacuum is available The gases will now leave through the exhaust crossover pipe Functional Check Check valve for proper operation binding condition must be corrected Check switch for proper operation Check hoses for cracking abrasion or deterioration Re place parts as necessary EARLY FUEL EVAPORATION THERMAL VACUUM SWITCH EFE TVS Operation At engine temperatures less than 120 manifold vacuum is directed from port D or 2 on the TVS to the EFE actuator which closes the heat valve and increases the exhaust flow th
28. ction Test Failure Diagnosis Guide fitting b A vacuum gauge attached to upper fitting should show a reading within 1 inch of the source vacuum Replace valve if it does not conform 3 Cold check below 70 F remove from engine a Cool valve to below 70 F b Apply a vacuum source to lower fitting c A vacuum gauge attached to upper fitting should not show a reading Replace valve if a reading is obtained Function Test of EFE System 400 Cu In Engine Before starting test the car should be cooled down so that the engine coolant temperature is below 120 F Before starting engine to make system check an extra person is required to start the engine while the testor observes the EFE valve for opening 1 Locate EFE valve and not position of the actuator arm 2 One man observes EFE valve when engine is started Valve should close when engine ts started cold The actua tor link will be pulled into the diaphragm housing 3 If valve does not close remove hose from EFE valve and apply in external vacuum source in excess of 8 inches Valve should close a If valve still does not close replace the EFE valve b If valve closes the problem is not the EFE valve See function test failure diagnosis guide for possible causes and repair the condition Then proceed with function test 4 Warm up engine until coolant exceeds 120 F 5 Observe valve to see if it has opened Valve should open 6 If valve d
29. ed HV are a of the EFE system These ports are open below 120 F and closed above 120 The lower portion of the TVV is a part of the EGR system on some engines and part of the distributor spark advance system on other engines Warm check above 120 F valve left on engine e Apply a vacuum source to the vertical port A vacuum attached to the port marked Should not show a reading Replace valve if it does not conform NOTE In this mode the HV port is vented to atmos phere Full Vacuum Advance System 400 Engine b Cold check below 120 F remove from engine or cool car overnight Cool valve to below 120 F Apply a vacuum source to the vertical port vacuum gauge attached to the port marked HV should show a reading within 1 inch of the source vacuum Replace valve if it does not conform EFE Valve a Apply a vacuum source in excess of 8 inches and ob serve for valve movement Valve should close The actuator link will be pulled in ward toward the diaphragm b Remove vacuum supply and observe for valve move ment Valve should open c To check diaphragm apply vacuum and seal off source Diaphragm should hold actuator link retracted for 1 mi nute d Replace diaphragm or valve parts as required if all the above checks are not met Condition Possible Cause Repair 1 Distributor advance unit not operating No advance at idle
30. ening the choke valve MOTOR BURETOR MANIFOLD VACUUM SOURCE Es SLMETALLIC THERMOSTATIC EXHAUST HEATER QAS 2 Figure 6F 2 Choke Modulator System Typical EXHAUST GAS RECIRCULATION SYSTEM E G R The Exhaust Gas Recirculation System is used on all 1975 Buicks The Exhaust Gas Recirculation System is used to reduce oxides of nitrogen emissions from the engine exhaust During the combustion process nitrogen which makes up GF 4 1975 BUICK SERVICE MANUAL TEAMBUICK for California located in line 80 percent of the air will tend to mix with oxygen at temperatures above 2500 F During the combustion proc ess temperatures in the engine s cylinders will go well above 2500 F which forms nitrogen oxides To lower the formations of nitrogen oxides it is necessary to reduce combustion temperatures This is accomplished by introducing exhaust gases into the engine intake mani fold which will enter the engine cylinders with the air fuel mixture for combustion The E G R valve remains closed during periods of engine idle and deceleration to prevent rough idle from excessive exhaust gas contamination in the idle air fuel mixtures All exhaust gas recirculation systems perform the same function however differences in operation of the system will be covered in the Diagnosis Section EARLY FUEL EVAPORA
31. hes the diaphragm spring will move the damper door downward opening the snorkel passage in order to get BU ICK 6 CONTROL SYSTEMS 6F 3 _ required for maximum acceleration Since failure of the thermo air cleaner will generally result in damper door staying in the downward position snorkel passage open failure will probably go unnoticed in warm weather In cold weather however owners will complain of leanness hesitation sag surge stalling When any type of lean operation complaint is received always test the thermo air cleaner for proper functioning before doing any work on the carburetor AIR INJECTION REACTOR SYSTEM A I R System reduces the hydrocarbon and carbon monoxide content of the exhaust gases by injecting air into the exhaust port of each cylinder The oxygen in the air reacts with the hot exhaust gas causing further combus tion in the exhaust manifold before the gas enters the exhaust pipe System is used on some 1975 Buicks The system consists of a belt driven air pump diverter valve check valve special intake manifold and cylinder head assemblies and hoses connecting the various compo nents Air Pump The air injection pump is a positive displacement vane type which is permanently lubricated and requires no peri odic maintenance The pump mounting bracket is attached to the front of the
32. into the hose and pump and causing damage This will protect the system in the event of pump belt failure abnormally high exhaust sys tem pressure or air delivery hose ruptures CATALYTIC CONVERTER The catalytic converter is an emission control device ad ded to the exhaust system to reduce hydrocarbon and carbon monoxide pollutants from the exhaust gas stream The converter contains beads which are coated with a catalytic material containing platinum and palladium Use of the catalytic converter has allowed the engine to be designed for improved fuel economy and driveability THE CATALYTIC CONVERTER REQUIRES THE USE OF UN LEADED FUEL ONLY Periodic maintenance of the exhaust system is not re quired however if the vehicle is raised for other service it is advisable to check the general condition of the cata lytic converter exhaust pipes and mufflers CHOKE AIR MODULATOR All 231 350 and 455 engine air cleaners will have a choke air modulator located in the bottom of the air cleaner to provide heated filtered air entering the choke thermo static coil housing When the air cleaner temperature is below a specified temperature the modulator is closed to slow down the rate of heating of the choke thermostatic coil for improved driveability As temperatures rise above the specified temperature the modulator will open allow ing normal circulation of heated filtered air to the choke housing heating the thermostatic coil and thus op
33. lt TVS il CARB HARNESS VACUUM BUA s URETOR HOSE CARBURETOR HOSE EGR EFE PURPLE TO TO TEE ORANGE TAPE CARB URETOR EGR TEE HOSE EGR EFE CHARCOAU SWITCH TO TEE CANISTER EGR EFE SWITCH TVS SWITCH YELLOW BB6F27 Figure 6F 37 455 Engine Vacuum Hose Routing AIR CLEANER CARB lt lt AIR TEMPERATURE INTAKE MANIFOLD SS gt MIXTURE TEMPERATURE e INTAKE MANIFOLD CARBURETOR CHOKE J COOLANT TEMPERATURE SECONDARY VACUUM b N CHECK VALVE CARB Ee 2 Bes L_JFULL vacuum SOURCE EGR MIXT TEMP CONTROLLED VAC FULL WITH 4 SEC RETARD DELAY EFE VALVE RS 2 5B6F28 Figure 6F 38 400 Engine Vacuum Hose Routing less California 32 1975 BUICK SERVICE camBuick com BACK PRESSURE TRANSDUCER TVV INTAKE MANIFOLD a TEMPERATURE 3 MIXTURE CU D AIR CLEANER CARB Wa T AIR TEMPERATURE INTAKE COOLANT TEMPERATURE vuro J CARBURETOR CHOKE LJ SECONDARY VACUUM BREAK DIAPHRAGM Z Z CHECK VALVE EGR MIXT TEMP CONTROLLED ADV FULL WITH 4 SEC RETARD DELAY COLD 5B6F29 Figure 6F 39 400 Engine Vacuum Hose Routing California
34. lt Tension eee See Cooling System Specifications 6F 20 1975 BUICK SERVICE coa ENGINE CUBIC INCH ENGINE HARDWARE USAGE CHART 250 231 350 455 400 260 1x revsystem _ ________ Tx J AIR SYSTEM 0 0 T T FRESH AIR INTAKE SYSTEM 8 x IDLESTOPSOLENOID 1721 THROTTLECLOSINGDASHPOT 1212 mx J l EGREFETHERMALVACUUMSWTCH O mx LEGRTHERMALVACUUMSWTCH _ 0 T __ T THERMALVACUUMSWTCH r L TL TT C T Tue r x T T 1 EFE VACUUM SOLENOID SWITCH J j TVS SWITCH D Jx jx x BACK PRESSURE TRANSDUCER VALVE __ T Tx Water SSES 77 DISTRIBUTOR VACUUM ADVANCE SPARK mx TT CHOKE AIR MODULATOR SWITCH AIR CLEANER _ x x T THERMAC AIR CLEANER THERMAL T 1x EFEDISTRIBUTOR VACUUM ADVANCE THERMAL VACUUM SWITCH x 7 7 O T PTAC RIPE DIFFUSER i n DISTRIBUTOR VACUUM ADVANCE RETARD DELAYVALVE T T REAR VACUUM BREAK THERMAL VACUUM SWITCH L 1 CALIFORNIA ONLY 2 ALL EXCEPT H SERIES 231 3 ALL EXCEPT 350 4BBL WITH A
35. m 231 350 and 455 Engines 6F 7 Checking Exhaust Gas Recirculation Valve Operation Engines 6F 7 231 350 455 Engines Exhaust Gas Recirculation System 6F 7 Early Fuel Evaporation System EFE 8 6F 8 Distributor Vacuum Advance Delay System 231 Engine 6F 11 260 Engine Early Fuel Evaporation System EFE ees 6F 11 Back Pressure Transducer Valve 6F 11 EGR Thermal Control Valve EGR TCV n nn aaa L LL 6F 12 400 Engine Exhaust Gas Recirculation System 6F 12 Early Fuel Evaporation System EFE 000 22 210 6 14 Distributor Vacuum Spark Retard Delay 6F 14 250 Engine Exhaust Gas Recirculation System EGR sts 6F 14 Early Fuel Evaporation System cccscccsssssssssscssesssessusssessessussecsessscssscssssssscsscusssssceecens 6F 14 MAINTENANCE AND ADJUSTMENTS Filter and Valve uqu 6F 15 Catalytic Converter a 6 16 MAJOR REPAIR Removal and Installation of Thermal Air Cleaner Parts
36. ng sen sor at B around the outside rim to prevent damage to the temperature sensing spring See Figure 6F 3 6 Reinstall vacuum hoses AIR PUMP Removal 1 Disconnect hoses from pump and valve 2 Loosen bracket to pump mounting bolts 3 Remove pump belt 4 Remove pulley to hub bolts and remove pulley 5 Remove pump 6 Remove valve from pump if pump is to be replaced Installation 1 Replace valve on back of pump 2 Position pump assembly on mounting bracket with holes lined up and install bolts loosely 3 Place pulley on hub and tighten pulley to hub bolts to 72 108 b in 4 Install pump belt over pulley 5 Move pump until belt is tightened to 60 85 155 and tighten bracket bolts 6 Connect all hoses to valve and pump 6F 16 1975 BUICK SERVICE MANOM Ga CENTRIFUGAL FILTER Removal 1 Remove pump 2 Insert needle nose pliers and pull fan from hub as shown in Figure 6F 5 It is seldom possible to remove fan without damaging it Care should be taken to prevent fragments from entering the air intake hole CENTRIFUG AL FILTER FAN Figure 6 5 Removing Centrifugal Fan From Hub Installation 1 Install filter fan by drawing it into position using pulley and bolts as tools Draw the fan down evenly by alter nately torquing the bolts making certain that the outer edge of the fan slips into the housing 2 Install pump new fan may be noisy for about 20 30 miles
37. oes not open remove hose from EFE valve to see if it will open Va ve should open If valve opens there is no air bleed for the diaphragm or the TVV plunger is stuck in the cold mode Replace TVV Failure EFE valve does not close 120 F 2 Malfunctioning TVV 3 Loose kinked pinched or plugged hoses or cracked T 4 Malfunctioning EFE valve diaphragm or ex Possible Cause 1 Coolant not below Repair 1 Remove TVV from engine for more rapid cooling 2 Replace part 3 Check hoses and connections and correct 4 Replace part ternal damage to link or arm etc 5 Check valve installed incorrectly 5 Install with tapered end toward vacuum source www contROL systems 13 valve does 2 Malfunctioning Stuck plunger 3 valve linkage parts 1 Plugged vent in TVV 1 Replace part 2 Replace part 3 Replace part Function Test of Individual Component Parts Check valve a Apply an external vacuum source to the tapered end of check valve b When vacuum source is sealed off leaving vacuum ap plied to valve there should be no vacuum loss in 1 minute Replace check valve if it loses more than 5 inch EFE Distributor Spark TVV In Intake Manifold Water Crossover 4 Port Type 400 Cu In Engine Non California The vertical port and the upper horizontal port mark
38. oolant temperatures the TVV is closed and the only vacuum path to the distributor is through the spark retard delay valve At this condition loss of vacuum advance when the throttle is opened will be gradual during a 4 second time period rather than immediately This feature is to improve cold driveability c At warm engine coolant temperatures the TVV opens and both vacuum paths to the distributor are available Under these circumstances the loss of vacuum advance with throttle opening will be instantaneous rather than delayed because vacuum will follow the path of least re sistance Spark retard delay with a warm engine is not desirable because of the possibility of spark knock CONDITION POSSIBLE CAUSE CORRECTION 1 Valve completely 1 Replace valve plugged or stuck Slow unstable idle frequent stalling 2 Restricted filter 1 Replace filter clean system Oil in air cleaner 1 PCV system plugged 1 Replace valve 2 Leak in closed venti 1 Clean system as required lation system 2 Inspect for leaks to atmosphere and correct as necessary THERMOSTATICALLY Carm BUICK EMISSION CONTROL systems 6F CLEANER SYSTEM CONDITION POSSIBLE CAUSE CORRECTION Hesitation sag and stalling during cold full open snorkel Start position 1 Thermac damper door in 1 Perform functional tests on Thermac system as described Poor fuel economy in closed snorkel
39. ound The vacuum gage should read zero If vacuum is indicated replace the solenoid Reconnect the lead to the engine oil temperature switch The vacuum gage should read zero If vacuum is indicated replace the engine oil temperature switch CHECKING E G R VALVE OPERATION ALL ENGINES Checking E G R Valve Engine at Operating Temperature The E G R valve cannot be disassembled and no actual service is required except that it should be checked for proper operation WARNING IF ENGINE HAS BEEN OPERATED CAUTION SHOULD BE USED WHEN CHECKING MOVEMENT OF VALVE STEM AS VALVE WILL BE HOT NOTE A cold override Www J BAM D u 19 CONTROL SYSTEMS tem is used on all models Disconnect sys tem prior to performing the on the car check of the EGR valve An outside vacuum source can be applied to the vacuum supply tube at the top of the vacuum diaphragm The diaphragm should not leak down and can be checked for freedom of movement by applying a 5 vacuum signal to the diaphragm and observing shaft movement MAINTENANCE AND ADJUSTMENTS P C V FILTER AND VALVE Replace positive crankcase ventilator valve every 24 months or 30 000 miles Replace PCV filter in the air cleaner every 30 000 miles more frequent under dusty conditions MAJOR REPAIR REMOVAL AND REPLACEMENT OF C C S UNITS The damper door is not serviceable The air cleaner assem bly must be replaced if the damper door is malfunctioning R and R
40. rn off the ignition and observe the vacuum gauge Vacuum reading should not drop immediately but should drop slowly taking about 2 to 5 seconds to go from 15 to 5 inches e If the vacuum drops too fast the TVV is leaking or the spark retard delay valve is malfunctioning Then Remove hose from TVV port marked 2 and plug hose Repeat step d If vacuum drops slowly replace the TVV If vacuum still drops too fast replace the spark retard delay valve EXHAUST GAS RECIRCULATION SYSTEM 250 CU IN ENGINE Funtion test the EGR valve as outlined under Checking EGR Valve Operation All Engines Testing EGR Thermal Vacuum Switch 250 Cu In Engine 1 Coolant temperatures above 100 F Connect vacuum gauge to port of the switch b Connect a hand operated vacuum pump to carburetor port and draw a vacuum There must be a vacuum reading on the vacuum gauge If not replace the valve 2 Engine coolant temperatures below 100 F remove switch from engine and cool if necessary a Connect vacuum gauge and pump to switch as in steps 1A and 1B above Draw a vacuum There should be no vacuum reaping on the gauge if there is replace the valve CU IN ENGINE Early Fuel Evaporation EFE System Check Check valve for proper operation A binding condition must be corrected Check solenoid for proper operation Check hoses for cracking abrasion or deterioration Re place parts as necessary
41. rough the intake manifold cross over The added heat from the exhause gas improves cold start per formance Above the switching point of the valve the valve closes and the spring loaded EFE valve is held open since there is no vacuum available The exhaust gas will now exit through the crossover pipe Functional Check 1 COLD ENGINE less than 120 coolant temperature disconnect hose from port D or 2 on the TVS and connect vacuum gauge to port Start engine If hoses are 6F 11 connected to the proper ports full manifold vacuum should be present at port D or 2 If not make sure manifold vacuum is present in hose connected to C or 3 If vacuum is present replace switch using a soft setting sealant 2 WARM ENGINE over 120 coolant temperature disconnect hose from port D or 2 on EFE TVS and connect vacuum gauge to the port Start engine If hoses are connected to proper ports less than 5 of vacuum Should be present at port D or 2 if more than 5 of Eum is present replace switch using a soft setting sea ant EARLY FUEL EVAPORATION CHECK VALVE EFE CV 260 CU IN ENGINE Operation check valve is used in the vacuum line from the intake manifold to the EFE TVS switch or the EFE DTVS The valve holds the highest vacuum reached to keep the EFE heat valve closed until the TVS switches modes The EFE heat valve could rattle without this valve under cer tain low vacuum conditions as during heavy
42. s well in cold weather The thermal air cleaner system consists of a heat stove a heated air pipe a nylon adapter elbow where necessary and an air cleaner containing a temperature controlled door operated by vacuum through a temperature sensor located on the bottom side of the air cleaner The heat stove is a sheet metal cover shaped to and bolted on the exhaust manifold Air drawn in along the lower edge of the stove passes across the manifold surface pick ing up heat The heated air is drawn out from the upper center of the manifold through the heated air pipe into the storkel of the air cleaner The temperature control air cleaner is designed to mix this heated air with cold outside air so that carburetor inlet air temperature averages about 115 degrees This mixing is done by a damper door The damper door is moved by a diaphragm type vacuum motor When there is no vacuum present in the motor the diaphragm spring forces the damper door downward opening the snorkel passage Whenever the engine is run ning the amount of vacuum present in the vacuum motor depends on the temperature sensor in the air cleaner which is located in the vacuum line between the intake manifold and the vacuum motor In the sensor a bi metal temperature sensing spring starts to open a valve to bleed more air into the vacuum line whenever the temperature in the air cleaner rises above about 115 Whenever the temperature falls below about 115 the
43. sensing spring starts to close the air bleed into the vacuum line allowing more manifold vacuum to reach the vacuum motor Whe never there is 6 inches or more of vacuum in the vacuum motor the diaphragm spring is compressed raising the damper door to close snorkel passage When the engine is not running the diaphragm spring will always hold the damper door to wide open snorkel passage position However when the engine is running the posi tion of the damper door depends on the air temperature in the air cleaner When starting a cold engine air cleaner temperature un der 85 the damper door will close off snorkel passage As soon as the air cleaner starts receiving hot air from the heat stove the sensor will cause the damper door to par tially open snorkel passage mixing cold air with hot air as necessary to regulate air cleaner temperature within 20 of the ideal 115 air inlet temperature If outside air temperature rises to 135 the air bleed valve in the sensor will be wide open so that vacuum to the vacuum motor approaches zero The diaphragm spring in the vacuum motor will hold the damper door to wide open snorkel position If outside temperature rises above 135 carburetor inlet air temperature will also rise above 135 While air cleaner temperature is being regulated ac celerating the engine hard will cause the vacuum level in the intake manifold and in the vacuum motor to drop Whenever vacuum drops below 4 inc
44. stems er 23 HOSE DIVERTER VALVE LUBRICATION RUBBER SIGNAL CLAMP MUST BE HORIZONTAL 309 LUBRICATION RUBBER HOSE A I R PIPE DIVERTER VALVE 6F10 Figure 6F 21 250 Engine 1 System Hoses HOSE A AiR CLEANER vatve VIEW lt gt IV CARBURETOR DIVERTER VACUUM FRONT OF CAR 7 5 VALVE DIVERTER lt e j VS TD v LUBRICATION VAN RUBBER I TEE FRONT OF CAR VALVE DIVERTER H LUBRICATION RUBBER FRONT OF CAR 6F11 Figure 6F 22 250 Engine A I R Hoses and Diverter Valve orae 1975 service cam Buick com CARBURETOR CLIP FUEL PIPE HOSE CLIP AMY T T DISTRIBUTOR CLIP 6F12 Figure 6F 23 250 Engine Distributor Vacuum Advance Hoses SOLENOID QJ FRONT OF CAR ENGINE LEVER ACCELERATOR CONT SUPPORT BRACKET amp ROD 2 Br E gt FRONT OF pP ACTUATOR amp ROD VACUUM FITTING 5B6F13 Figure 6F 24 250 Engine EFE Valve www contro systems 25 HOSE EGR EFE SWITCH TO HOSECARBURETOR HosE EGR EFE SWITCH HOSE EGR EFE TO VACUUM FITTING TO EGR EFE SWITCH EFE PIPE GREEN VACUUM SOURCE YELLOW 5 32 X 16 BLUE 7 322X85 5 32 8 n YELLOW E G R FROM AIR N AIR WIRING HOSE EGR EFE HARNESS CLIP SWITCH TO EGR PINK 7 32 X 22 VIEW OF FRONT WIRING OF CARBURETOR HARNESS 4
45. ting 1 Reassemble and replace or tighten hose clamps 4 Malfunctioning divert 1 Replace valve er valve 5 Malfunctioning check 1 Replace valve valve 6 Malfunctioning pump 1 Replace pump CATALYTIC CONVERTER ALL Condition Possible Cause Correction Exhaust system noisy 1 Exhaust pipe Joints 1 Tighten clamps at joint loose at catalytic converter 2 Catalytic converter 1 Replace catalytic converter ruptured 3 Loose or missing 1 Tighten or replace Recharge catalyst replacement catalyst as necessary plug www MISSION CONTROL 5 5 5 6F 7 DUI ERE Mp Poor car performance 1 Failed catalytic 1 Replace catalytic converter converter Ignition system and AIR system should also be diagnosed and repairs made if necessary B B size particles 1 Failed catalytic 1 Replace catalytic converter coming out of tailpipe converter Ignition system and AIR system should also be diagnosed and re pairs made if necessary CHOKE AIR MODULATOR SYSTEM 231 350 AND 455 ENGINES Condition Possible Cause Correction Poor driveability after 1 Choke air modulator 1 Locate restriction and warm up choke not system plugged correct as necessary releasing Poor driveability 1 Modulator valve stuck 1 Replace valve during warm up choke in open position releasing to soon OO aaaea a EVAPORATIVE EMISSIO
46. ting system would upset the air fuel mixture causing rough idle For this reason a flow control valve is used which restricts the ventilating system flow whenever intake manifold vacuum is high See Figure 6F 1 PLUNGER BODY 6 1 Figure 6F 1 Positive Crankcase Ventilator Valve An engine which is operated without any crankcase venti lation can be damaged seriously Therefore it is important to replace the ventilator valve periodically CAUTION engine is idling too slow or rough this may be caused by a clogged ventila tor valve or plugged hose therefore never ad Just the carburetor idle without first checking the crankcase ventilator check valve and hose After installing a new ventilator valve readjust engine idle if necessary All cars have a closed P C V System With this system any blow by in excess of the system capacity from a badly worn engine sustained heavy load etc is ex hausted into the air cleaner and is drawn into the engine THERMOSTATICALLY CONTROLLED AIR CLEANER Since past model carburetion was as lean as possible con sistent with good driveability with inlet air temperatures es this still leaner carburetion 15 only ako COR the heated air system With the heated air system operating inlet air temperature is around 115 degrees after the first few minutes of operat ion this makes use of leaner hot weather calibration possible and the car still responds and drive
47. uld re main in position closed snorkel passage If it does not there is a vacuum leak in diaphragm assembly Replace diaphragm assembly Sensor Check Quick Check of System l Start test with engine cold air cleaner at a temperature below 85 degrees If the engine has been in recent use A I R PUMP DIAGNOSIS CHART ALL allow it to cool Removing the air cleaner from the engine and placing it on the bench will aid in quickly cooling the sensor 2 Observe the damper door before starting the engine it should be in the open snorkel position 3 Start the engine and allow it to idle Immediately after starting the engine the damper door should be in the closed snorkel passage position 4 As the engine warms up the damper door should start to allow outside air and heated air to enter the carburetor inlet 5 The system is operating normally as described above If the air cleaner fails to operate as above or if correct operat ion of the air cleaner is still in doubt proceed to the thermometer check of sensor Thermometer Check of Sensor l Start test with air cleaner temperature below 85 degrees If engine has been run recently remove air cleaner and place on bench this will help quickly cool the air cleaner Remove air cleaner cover and place Tool J 22973 Ther mac Thermometer as close as possible to the sensor Let air cleaner cool until thermometer reads below 85 F about 5 to 10 minutes Reinstall air cle
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