Diagnosing No-Starts on Some 740/940 Volvos
Contents
1. Figure 13 In turbocharged replace the Charge engines the Charge Air Air Overpressure Overpressure Switch CAOS Switch On the other connector top arrow turns half of the connector current off to the fuel injec check continuity to tion relay if boost pressure 36 2 through one is too high thus interrupting fuel supply to the engine It is located above the driver s knees next to steering col umn Remove trim Unclip of the yellow black wires The other vellow black wire from the CAOS runs the translucent connector to 14 on the block and check for continuity per A connector and text then on to ECU End of my expertise 7 Fuel injection component circuit Electrical If you get spark and fuel then use Figure 14 to run voltage tests across each of the other fuel injec tion components First check for 12 volts DC across the 1 fuel injector green wire and ground with ignition On Next work backwards through ballast resistor connector and then the auxiliary suppres sion relay A null reading on a positive outlet of a component and 12 volts on the input side identifies that component as faulty And make sure there are no broken wires by checking for continuity from one component to the next See Sidebar 5 for location of auxiliary suprression relay on 940 One of the little joys in life is isolating and diagnos ing a no start fault in an automobile engine hope this guide has helped you make in2. If the camshaft doesn t rotate your timing belt is likely broken 4 Electrical Pull the coil high tension wire from the distributor and hold its end ing is fine Inset Shows ignition about 1 8 from metal on the engine block Figure 1 Danger Use a plastic grip coil leads and center post high or tongs never insulated metal pliers or your bare hand Perform test in dry tension wire secondary wind environment With someone cranking the engine for 2 3 seconds check for good ing to the distributor spark Don t overdo cranking as some manuals warn it could damage sensitive electronics If no spark go to Step 4a If good spark is present go to Step 5a 4a No spark In olden days no spark from the ignition coil usually meant it was faulty or the coil primary contacts 1 and 15 were corroded These days other possible culprits include the Hall sensor or Power Stage and they cannot be discounted Parts suppliers also call the Power Stage an igniter ignition amplifier etc With ignition 3 Sidebar 1 Notes Hints and Observations e For purposes of this guide the key in the position of the ignition switch means ignition On or ignition Run The key in the position is ignition Start e An old battery gt 5 yrs may give spurious results because it quickly runs down in tests j Recharge as necessary Subsequently if it fails to hold charge replace it e The dodet tester bee
3. Wy put 3 x d pe A e 7 os SA er h a gt ae a 4 4 e SS a ae N Argh l E i an biii a i ji TETERNO hac NaN fi y eA Bs eines s Po LZ f s ATA m aa 37 ase A R 4 g A X i a i A The auxiliary suppression relay The RPM sensor arrow sits atop arrow is on the passenger side exposes the Power Stage arrow the bellhousing behind engine front wheel well near battery on the driver s side front wheel low against firewall Very confined There are no ballast resistors well space Step 4b lists website with instructions for careful removal Spare parts to carry in case of breakdown A lot of the spare parts can be found at junkyards recommend carrying the following 1 ignition coil test at junkyard should meet following specs 1 2 ohms between primary windings 1 and 15 6 kohms 9 kohms between 1 or 15 and center post 2 Power Stage 3 auxiliary suppression relay 4 fuel injection relay 5 distributor with Hall sensor or rpm sensor new 6 spare timing belt and at least one fan belt 7 extra fuses especially 25 amp fuse 1 for the main fuel pump 8 tools to handle above jobs 9 this how to guide and possibly 10 main fuel pump The main fuel pump is expensive At the very least carry information for ordering one so you don t get ripped off With overnight freight it will probably be cheaper than buying through a local dealer who may take advantage o
4. for the in tank pump to exclude it in this test and hit Start for a couple of seconds If you had left fuse 11 in a functioning in tank pump would still deliver fuel falsely implying a working main fuel pump The engine will not start with a faulty main fuel pump and cannot start relying on a functioning in tank pump alone If no fuel is delivered go to Step 5b If you get fuel the main fuel pump and fuel injection relay work Go to Step 7 Re insert fuse 11 5b No fuel delivery No fuel means a faulty main fuel pump fuel injec tion relay or their circuits Test the main fuel pump first Danger Set car up on good jackstand on flat surface transmission in neutral wheels blocked handbrake set Use jack as backup support Go under car and push on both feed wires to the main fuel pump while an assistant cranks the engine A functioning main fuel pump emits a whiney tinny whir at ignition Start or engine Run FYI on the other hand a functioning in tank fuel pump emits a soft hum at ignition On If there is no whir from the main fuel pump check for 12 volts DC across the leads when engine is cranked Figure 10a Also make sure negative lead is grounded If 12 volts is present because a main fuel pump is not inexpensive doublecheck by running a long positive lead probe Caution Sheathe positive probe so it doesn t touch metal ground while setting up and only unsheathe for test directly from the ba
5. pry open hold down latches on A connector to expose contacts which are numbered Test continuity between 14 on A block to correct yellow black wire of Charge Air Overpres sure Switch or for nonturbos to 86 2 on f i relay My expertise ends here Ba right front door jamb Feed Circuit for Fuel Injectors LH Jetronic 2 2 Ground ya ee Powers y x Steering as Fluid Reservoir SS F driver s side engine compartment Injection Auxiliary probe across g S by multimeter uppression Lee Ballast Resistor CA Y gt Fuel Injectors BN Brown R Red See x D BL Blue Injector Ao 3 SF ai Ballast Y llow Hid fs GN Green iss SB Black driver s side above battery Figure 14 With ignition On first check for 12 volts DC nor mal between Green lead and ground at fuel injector 1 Next work backwards through the connector at the ballast resis tor and then the auxiliary suppression relay A null result on output connection of a component and 12 volts on the input end identifies that component as faulty See Sidebar 3 continuity between 86 2 of fuel injec tion relay and 14 on block A connector Figure 12 end of my expertise In turbos find the Charge Air Overpressure Switch CAOS Figure 13 Pull connector apart and check continu ity across CAOS the black wires in one half of the connec tor If no continuity
6. CU and for plies the RPM sensor A properly functioning Hall sen turbos through the Charge Air Overpressure Switch connec sor also closes electromagnetic switch 2 EM2 onthe tor When EM2 closes it feeds current to the main fuel pump fuel injection relay Figure 4 feeding current to the through junction 87 2 main fuel pump To observe EM2 release then lift and of the Hall sensor and RPM sensor are supposedly identical but cannot personally vouch for that fact rarer dD ati P Wi he i t Biriani Figure 5 Pull out and fuse cover plate and remove the cigarette lighter shelf Phillips screw beneath plastic snap off cover plate Release and lift tray out The fuel injec tion relay arrowed has a white housing and is left most second row behind the fuse tray work the relay tray into the open Figure 5 Remove relay from its tray socket and gently pry whitish cover off to expose the two switches EM1 and EM2 copper coils Reinstall the relay sans cover into its blue female socket in tray Turn ignition to Start EM 1 frontmost in tray and EM2 should both close Figure 6 If EM2 closes then the Hall sensor works and either the ignition coil or Power Stage is bad Step 4c If EM2 is open then the Hall sensor or RPM sensor is most likely bad First check for proper inputs to Hall sensor Sidebar 2 If inputs are there replace distributor If inputs are not there the prob lem could lie wit
7. Diagnosing No Starts on Some 740 940 Volvos Like those similar to my ate fe 1A 5 Tahoe Py FNA en Bera a a em gen gt ONE SRS ee e 1987 740 Volvo with B230FT engine and Bosch LH Jetronic 2 2 Fuel Injection System Pay 6 only if it helps How s that for a satisfaction guarantee from chasing after red herrings when my car died Learn from my mistakes Use this step by step guide to track down the most likely suspects for no starts on some 740 940 Volvo models 2008 by Frederick Su All rights reserved A bytewrite LLC publication 740 940 No Start Flow Chart mainly B230FT LH Jetronic 2 2 read accompanying text of how to article follow safety precautions Quick Tests Involved Tests e e 0O 0 53 0 cC T gt 0O battery starter ignition circuit fine Yes No J gt replace battery starter or fix ignition fault No fill tank or got gas fuse 1 ok replace fuse REPLACE TIMING BELT does camshaft rotate No Sb Push in main pump _ Yes feed wires at ignition Start Engine run ensure good electrical connection Remove fuse 11 fuel out of fuel rail Yes direct feed to main fuel 12 volts at main check injection fuel pump components under hood with ignition On 6 test f i relay EMI and EM2 No 6a i 0 volts on jiggle relay Keep goin aa a output lead Seater Bs st
8. EPLACE wires of CAOS CAOS Continuity btwn CAOS amp 86 2 fix broken connection Also called Igniter by some parts suppliers to 20 on ECU No Start Flow Chart 5 This guide is a best faith effort provided by someone who is not a professional mechanic Users assume all risks and liabilities including material damage and costs that may be caused by incorrect information and injury and or death caused by not following safety precautions Use of this article is an agreement that parties shall hold harmless the author and bytewrite LLC Observe all safety precautions right up to the fuel system Electronic Control Unit ECU and ignition Electronic Control Unit IECU where my expertise ends Having chased red herrings and needlessly spent money as a do it yourselfer now adhere to the motto Be informed Check twice buy once Te are many possible causes for a no start While not exhaustive this manual covers the most likely suspects Diagnosis is done without the use of fault codes or an oscilloscope How so In the end a computer delivers certain voltage or current values to components under certain conditions and a lot can be discerned by testing for those end results My Volvo is a 1987 740 turbo B230FT L H Jetronic 2 2 So instruc tions are mainly for this model but advice here may help you with other models and variations Exceptional wiring diagrams are available for different fuel injection
9. Fuel Injection Relay of engine Start ic ff to batter Problem is fixed If to ignition then battery no start go to Step With ignition On Ab connects to ground through ECU closing EM1 to lambda 4b No spark A 5 sond malfunctioning ee suse 1 sensor connector beneath in line on the overhead Charge Ale distributor on back of engine near distributor near i Overpressure in tank e Switch main fuel pump firewall To test inputs per Step firewall Figure 3 n pump i ignition 4b unplug connector by pressing also means no spark Start or up on spring clip at bottom and from the ignition anp ne mn gently pulling back Inset Num coil Starting in ho Hall Auxiliary bers denote Hall sensor terminal 5 Sensor Suppression 1988 Volvo switched Relay leads Probe terminals for proper inputs Sidebar 2 Terminal 3 is red wire over to an RPM sen sor instead located Figure 4 Schematic for the fuel injection relay 12 volts is on the bellhousing always present at junction 30 Ignition On closes EM1 by see Sidebar 5 that runs off the crankshaft Functions providing a path to ground through the ECU EM1 then feeds current to EM2 through junctions 87 1 and 85 But EM2 does not close until the Hall Sensor detects camshaft rotation i ignition Start or engine running and completes the circuit In this article any mention of the Hall eee also im to EM2 through the Electronic Control Unit E
10. and ignition systems at www autoelectric ru auto volvo 740 1989 740 89 htm for the 740 and 7 http www autoelectric ru auto volvo 940 1993 940 93 htm for Figure 1 Test for spark Pull coil high tension the 940 wire from distributor Use plastic grip to hold end 1 8 from metal on engine block while an assistant cranks engine Don t overdo cranking A dead engine has three possible culprits mechanical electrical or fuel 1 No or little noise on ignition Start engine does not turn over or crank or grinding screech Check for 12 volts DC at battery terminals note a faulty bat tery will quickly drop to 9 10 volts when under load Also clean battery cable ends and battery posts Other possibilities are the starter solenoid and starter grinding screech and ignition switch and circuit 2 Engine cranks but doesn t run on ignition Start the symptom for all following tests Be sure you have gas and not water once had that problem as Sl Then check that fuse 1 main fuel pump and fuel injection system is intact Figure 2 Check for 12 volts DC between 15 terminal on igni 3 Mechanical Check timing belt Lift oil filler cap to view overhead camshaft tion coil and ground with igni tion On Ground is sanded bare metal on hood hinge 12 volts between 1 and ground implies that the primary wind while an assistant cranks engine If camshaft rotates the timing belt is fine
11. art r 12 volts on ignition tart is found input end clean f i relay check connection junctions REPLACE at 87 2 or find broken ensure good FI wire between 87 2 connections COMPONENT and main fuel pump Ign Ignition f i fuel injection CAOS Charge Air Overpressure Switch IECU ignition electronic control unit ECU fuel system electronic control unit end of my expertise to 17 on ECU test continuity 277 E btwn CAOS amp 14 on A connector 2008 by Frederick Su All rights reserved A bytewrite LLC publication pump whir Ono Spark 4a Ign On 12 volts DC at NO trace back terminal 15 in primary in Ign circuit Yes Ign On 12 volts DC at No rai terminal 1 in primary COIL mana Yes back clean contacts Yes P hit Start problem fixed Engine run de V 0 000 Ag Test VAC btwn 0 015 vAC All inputs to Yes as sere a R W coil 1 Power Stage A od lead and gnd present Yes correct inputs TTI X DR to Hall sensor sis more SENSOR REPLACE MAIN FUEL PUMP REPLACE IGNITION COIL jumper between 30 and 87 2 whir at main fuel pump 12 volts at junction 30 Nonturbo INJECTION REPLACE FUEL RELAY trace backwards in circuit Check continuity BS from 86 2 to 414 _ a 6b on A Connector Turbo Continuity btwn 2 blk R
12. f your situation can t imagine trying to replace a main fuel pump yourself while on the road It s a tough smelly job difficult enough to do at home Also you want a new main fuel pump because you don t want to have to replace a used one in a few years Other helpful sources 1 www autoelectric ru auto volvo 740 1989 740 89 htm 2 www autoelectric ru auto volvo 940 1993 940 93 htm 3 Haynes manual Volvo 740 amp 760 4 Bentley Volvo 240 Service Manual 5 http www volvoclub org uk fag Electricallgnition html BasicOperationandTroubleshootingoftheEZ 6 www swedishbricks net 7 Google searches on Volvo specific topics Comments Email fred bytewrite com please write Volvo in the Subject line Fred is a physicist turned writer who works on his Volvos when he has to In his award winning novel An American Sin ISBN13 978 0 9711206 0 0 price 15 the protagonist s 1970 145 Volvo breaks down outside Missoula Mon tana leading to a meeting with a pivotal hero of the Vietnam War More info at www bytewrite com An American Sin can be ordered at your local bookstore or see next page 9 Print amp enclose w order If this booklet helped and saved you money please send a 6 check payable to bytewrite to bytewrite LLC P O Box 2635 Bellingham WA 98227 USA Also consider ordering a copy of An American Sin regularly 15 info at www bytewrite com from your local book store Or order an autographed copy d
13. formed choices Remember check twice buy once Good luck Sidebar 2 Normal Readings Author s results in parentheses for an engine that runs Hall Sensor Figure 3 inset test between voltage Terminal 3 red amp Ground 12 VDC 11 14 VDC ignition On voltage Terminal 2 blue amp Ground 5 VDC 5 VDC ignition On Figure 15 Remove the Power Stage Figure 15 Power Stage connector test between also see Figure 7 by voltage Pin 1 amp Ground 12 VDC 12 17 VDC ignition On depressing the spring voltage Pin 4 amp Ground 12 VDC 12 18 VDC ignition On clip and gently tugging resistance Pins 1 amp 4 match primary coil resistance 1 ohm 13 3 ohms ne Ponueeret cowl lies The numbers identifying resistance Pin 2 amp Ground 0 ohms 0 2 ohms key out of ignition Henin connectots are voltage Pin 5 amp Ground 2 VDC 2 13 VDC leads disconnected from coil exposed by pulling the terminals 1 amp 15 at ignition Start rubber boot back Sidebar 3 Test the Auxiliary Suppression Relay LH Jetronic 2 2 For instance to test the auxiliary suppression relay pull the relay apart and test the BN or R lead of connector left for 12 VDC should always be present even with key out of ignition switch If no 12 V check back in the feed circuit If you get 12 V put the relay back together and pull the ballast resistor connector apart ee right A
14. h the IECU Figure 13 End of my expertise A new RPM sensor is no longer cheap And replacing it because of the confined space is no walk in the park Breaking it may necessitate pull ing the transmission Visit http www volvoclub org uk faq EngineSensors html Crank_Postition_ Sensor for instructions Yes they misspelled Position 4c No spark The presence of 12 VDC between 15 and ground does not exonerate a faulty Power Figure 6 a The two relay switches fine copper wire are shown EM1 is topmost and frontmost when installed in ve hicle and EM2 is shown below it in photo In this case EM1 is closed ignition is On while EM2 is open b At ignition Start or engine Run both switches should close as shown Stage The Power Stage Figure 7 uses a transistor here to amplify and switch the battery direct Rower Stage Figure 7 The Power Stage located near battery is a transistor current amplifier that switches direct current on and off in concert with the IECU and Hall sensor In effect it provides an alternating current to the primary winding of the ignition coil to induce high voltage in the secondary Note ballast resistor and directly above it its connector Also see Figures 14 and 15 and Sidebar 5 for 940 location current on and off essentially sending an alternating current to the primary winding of the ignition coil thus stepping up voltage in the sec
15. irectly from the publisher and save 20 plus get free shipping in U S You ll be supporting a very small press and keep information flowing for do it yourselfers Thank you Name gt S What do you want written in your autographed copy of An American Sin Address Email Date Title Price Quantity Total A Diagnosing No Starts on Some 740 940 Volvos 6 00 U S X 1 6 00 already downloaded O An American Sin regular price 15 12 00 U S x with above paid download it s 20 off Shipping in U S Free Shipping to Canada 4 66 outside U S and Canada please email fred bytewrite com for shipping cost Publisher pays WA State Sales Tax Make check out to bytewrite Grand Total Thank you 10
16. ondary winding to fire the spark plugs Instead use the AC alternating current voltage set ting on your multimeter Figure 8 Isolate the Power Stage by discon necting the Red White lead from terminal 1 on the ignition coil and test VAC between Red White lead and ground at ignition Start If you get 0 000 0 015 VAC check for correct inputs to the Power Stage see Sidebar 2 If Power Stage inputs are present within reason replace the Power Stage If you get V gt 0 30 VAC between Red White lead and ground this implies the Power Stage is working properly Replace the ignition coil 5 Fuel System Good spark implies a problem in the fuel injection sys tem Consult the wiring diagram available at autoelectric listed earlier Their schematics also show locations of various components on the car 5a Test Fuel delivery Open the fuel rail Danger No smoking and Ap EA y Figure 8 Disconnect the Red White lead from 1 on ignition coil Use the AC alternating current voltage setting on your multimeter and test voltage between Red White lead and ground at ignition Start A reading of 0 000 0 015 VAC implies a faulty Power Stage or a fault feeding the Power Stage In this photo 4 51 VAC across 1 and ground with all leads connected of course represents a properly running engine On the 940 I got 2 6 2 8 VAC with engine running insert 17 mm inlet into a jar or can Figure 9 Pull fuse 11
17. or at the main fuel pump implies a fault in the fuel injection relay or its feed circuit With ignition Start does EM1 and EM2 close If yes check connection at 87 2 or fix broken wire between 87 2 and main fuel pump If no go to Step 6a kN ice 6a Fuel injection relay circuit Electrical If EM1 and EM2 do not close i A at ignition Start first try jiggling the relay as you hit Start It could just be poor electrical connections If so clean the contacts If still no go pull the up per male relay out and use a jumper wire to momentarily connect 30 and Figure 11 In Step 6a with key out of ignition jump the con nections 30 and 87 2 on the blue female connector If you hear a whir from the main fuel pump then the fuel injection relay is faulty 87 2 at the blue female socket of the fuel injection relay Figure 11 As 30 is always hot i e always at 12 volts DC do this test with the key out of the ignition You should be able to hear a whir within the passenger compartment If you like have an assistant listen underneath the car If there is a whir replace the fuel injection relay If there is no whir check for 12 volts at 30 If no 12 volts trace back in that circuit If 12 volts is present at 30 in non turbos check Figure 12 The A connector block and ECU are located behind the trim by the front passenger s right foot Gently
18. p mode on a digital multimeter is great for continuity tests but it cannot discern a short circuit 0 1 ohms use lowest ohmmeter setting instead Also digital multimeters have dif ferent resistance ranges over which they will beep for continuity checks For instance my old Fluke 73 Series multimeter beeps for resistances lt 210 Qs my Cen Tech model beeps for resistances lt 60 Qs e Realize that a probable cause for a no start may be a broken wire which can be confirmed by a null con tinuity test Breaks are more likely within the engine wiring harness which is exposed to oil heat and in some cases chafing rather than for instance wiring in the passenger compartment Continuity and resistance tests are run with the key out of the ignition e Doublecheck multimeter leads are solidly connected when running tests Your wallet depends on it e Once diagnosed some faults are easy to fix such as replacing a faulty fuel injection relay ignition coil or Power Stage Others are more involved such as replacing a timing belt or main fuel pump On check for 12 volts DC at the primary lead of the coil between 15 and ground see Figure 2 If no 12 volts trace back in ignition circuit Also check for 12 volts DC between 1 and ground if null replace ignition coil Otherwise clean 15 and 1 terminals and leads and high tension lead and center post con tact Attempt restart LH Jetronic 2 2 B230FT
19. t ignition On check for 11 12 VDC at the ballast Connector for aux resistor connector by probing the GN R lead coming from the is Connector for ballast iliary suppression auxiliary suppression relay If you get 0 VDC or otherwise low resistor retay reading then replace the auxiliary suppression relay Sidebar 4 The Ballast Resistors The ballast resistors in the LH Jetronic 2 2 system as far as understand it act as shunt resistors The Bentley manual claims that their main purpose is to limit current to the ignition coil at low engine speeds The Haynes manual claims the resistance of the ballast resistor total should be 1 ohm There have been misprints in the Haynes manual particularly when they said the resistance of the second ary windings of the ignition coil is 6 0 to 9 5 ohms when it should be 6 0 kohms 9 5 kohms I don t know what they mean by total There are 4 resistors with 2 each connected in series have tested ballast resistors on three 740 Volvos and always got 12 ohms for the two resistors in series adjacent terminals Sidebar 5 Auxiliary Suppression Relay Power Stage and RPM Sensor Locations on the 940 LH Jetronic 2 4 A W Sa lt i aes 3 S 2 gt 7 gt A ay E ke F k 2 A 4 Dow wa Fa x SAR t lt k lt a u gt A A l t N x 7 P a ha Tet 4 r 7 I eet S gt Da ro Dy 4 4 Par DS lt a i 4 y 4 i P 4 ww F gt J 4
20. ttery post and a ground lead from the door buzzer terminal of Figure 10b and probe the main fuel pump contacts directly You re doing this test because sometimes the electrical leads don t seat properly If no whir replace main fuel pump If whir is present then clean all electrical contacts as best as pos sible they re recessed reconnect and push leads into pump while an assistant cranks engine I had to grind down the plastic housing of the positive lead by 2 mm to ensure a better fit into the pump connector If engine Starts then it was a bad electrical connection to the main fuel pump If 12 volts is not present go to Step 6 i Ser TA r a Figure 9 Pull fuse 11 Use 14 mm and 17 mm wrenches to break open the fuel rail Insert the 17 mm inlet into a container to check for fuel flow while an assistant cranks the engine ignition Start Careful Fuel can come out fast The connectors are arrowed Figure 10a Underneath the vehicle insert positive probe of multimeter into the positive lead to the main fuel pump and insert the negative probe of the multimeter to ground of b Have an assistant crank engine ignition Start while you check for 12 volts DC TEHA Figure 10b Set up a convenient ground by screwing an elec trical connector onto the driver s side door buzzer switch Note multimeter probe in 6 Fuel injection circuit Electrical Lack of 12 volts serted in connect
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