Fuel SyStem - Central States Bus Sales, Inc.
Contents
1. To Engine Return From Engine Fitting has a copper gasket which seals against male flares on engine fittings This gasket must be installed to prevent leaks 0087409 Fuel System Assembling Fittings 1 Cut tubing squarely Maximum of 15 angle allowable Use of Parker tube cutter PTC 001 is recommended 2 Check that port or mating part is clean and free of debris Insert tubing into fitting until it bottoms on seat 4 Tighten nut with wrench until one thread remains visible on the fitting body This will allow for a number of remakes Or turn down the nut until finger tight then tighten as indicated below TUBE SIZE TURNS BEYOND HAND TIGHT Yq 3 3A amp 2 4 5 amp 3 4 3 When installing item 10 Tighten one turn beyond finger tight Then Con tinue turning to orient barb 627 0 BLUE BIRD 628 0 BLUE BIRD VISION cenvice manuan Fuel Filters The fuel water separator and primary fuel filter is located just forward of the rear axle on the inside of the left hand frame rail on the driver s side This separator must be drained daily to ensure the fuel is clean and free of water as it enters the secondary fuel filter The fuel water separator and primary filter cartridge Part Num ber R90 BB 02 must be changed at a minimum at prescribed in tervals dictated by the Level 1 Preventative Maintenance Schedule established by Caterpillar This interval is 11 000 miles 17 7002. Front amp rear holes 100 gallon fuel tank I iS iS VISION SERVICE MANUAL 632 0 BLUE BIRD Fuel Tank Draining the Fuel Tank Caterpillar scheduled Level 1 Maintenance also requires that the fuel tank be drained of accumulated sediment and water To drain the fuel tank 1 Observe all safety warnings and environmental cautions See the Intro duction chapter of this service manual 2 Remove the drain plug from the bottom of the fuel tank 3 When only clean fuel is being discharged from the tank replace the drain plug Install finger tight Wipe the exposed threads and apply Loctite 557 with Teflon to the exposed threads Continue to tighten the plug 1 turns 4 Wipe clean and ensure there is no leak Fuel Tank Removal 1 Using the drain plug in the bottom of the tank drain the fuel into suit able containers Loosely install the plug to prevent entry of debris Place a suitable support device under the tank Remove 6 hexhead screws from the filler tube cover Remove 4 bolts from the front tank guard Remove 4 bolts from rear tank guard Ox ga oh Remove 2 bolts from each end of each tank support Lower the tank care fully until it is possible to remove the fuel lines and wiring from the top of the tank There is a loop of approximately 18 inches 457 mm slack at the top of the tank for this purpose 7 Remove all fuel lines and the filler tube Carefully cover each opening as it is opened to pre
3. Nm 16 Install the drain plug in the bottom of the fuel tank finger tight Then apply a bead of Loctite 557 with Teflon or equivalent to the exposed threads Continue to tighten 2 full turns Wipe clean Accelerator Control Electronic The Vision s throttle control regulates engine speed not by direct mechanical link age but by electronically communicating the position of the pedal to the engine s Electronic Control Module ECM The ECM in turn controls the engine s fuel system to adjust engine speed When the pedal is pressed its lever arm rotates a spring loaded mechanism in side the throttle assembly s upper housing Attached to the side of the housing is an electronic position sensor which varies a signal it sends to the engine ECM The signal modulates according to the position of the rotating part of the pedal assembly Being electronic the accelerator is mounted entirely inside the bus with no part of it extending through the firewall The assembly is not rebuildable therefore it must be replaced as a unit if damaged or faulty The pedal position sensor requires no adjustment and is not rebuildable However it is replaceable as a separate unit from the pedal assembly Blue Bird kit 0064032 Throttle Position Sensor The throttle position sensor receives a 8 volt DC supply voltage from the engine ECM drawing less than 40mA of current It s electonic circuitry senses the accelera tor pedal position and genera
4. SENSOR RETURN oren K F M om DEPA Throttle Sensor 2 an XDA on DA A on DI m sci 639 Engine Control Module ECM THROTTLE RETURN THROTTLE SIGNAL 1 THROTTLE POWER SENSOR POWER 5 VOLTS THROTTLE SIGNAL 2 SENSOR RETURN BLUE BIRD
5. AL Pulse Width Modulation Several components on the Blue Bird Vision employ pulse width modulation rather than mechanical rheostats or resistors These include the acellerator pedal daytime running lights and instrument lighting This illustration explains the basic principle of Pulse Width Modulation Uniform Square Waveform WAVELENGTH O O WAEN WAVELENGTH In this unmodulated wave Wavelength and therefore Frequency is constant Amplitude wave height is constant Pulse Width the positive portion of the wave is constant Note that in this example the Pulse Width occupies 50 of the total wavelength PULSEWIDTH lt PULSEWIDTH lt PULSEWIDTH 50 50 50 50 50 50 Pulse Width Modulation PWM WAVELENGTH WAVELENGTH WAE In a PWM circuit information is conveyed by varying the percentage of total wavelength which is occupied by the Pulse Width Wavelength therefore Frequency is constant 6 3 6 Amplitude is constant Pulse Width varies Note that now the Pulse Width varies PULSEWIDTH PULSEWIDTH PULSEWIDTH independently of Wavelength The Pulse Width to Wavelength ratio is expressed as a percentage and is referred 20 pro CS 40 poa gt 60 DUTY CYCLE to as Duty Cycle 0 BLUE BIRD Auto Calibration The ECM is programmed to automatically re calibrate its responses to the throttle position sensor signal each time the ignition is turned on Initially the ECM interprets a 22 pulse wave as a
6. Checking Supply Volt ground Voltage can be checked by using Caterpillar s breakout test lead This should indicate that 8 VDC is being delivered by the ECM to the harness connector If i g Breakout the voltage is out of range lead E e Check the integrity of the vehicle wiring harness from the connector to the ECM Repair as necessary e If connections and harness test l satisfactorally the problem may be due to a damaged ECM Refer to Caterpillar trouble i shooting guidelines 4 Turn ignition off Connect the breakout test lead as follows 4 1 Connect the breakout lead in line with the accelerator wir Meter set to read Volts DC ing harness Connected to positive and negative plugs of Breakout Lead BLUE BIRD VISION SERVICE MANUAL 638 BLUE BIRD 4 2 Connect the red lead of the meter to terminal C of the breakout test lead accelerator pedal position white circuit 4 3 Connect the black lead to terminal B of the breakout test lead accel erator switch sensor common black circuit 5 Set the meter to measure duty cycle percentage Turn the ignition on 6 Check the duty cycle readings with the accelerator at idle and at full RPM position Compare the readings to the values shown here With the Position Sensor attached to the Accelerator Pedal Assembly readings should be Idle 10 22 Full Throttle 75 90 If the Position Sensor is removed from
7. FUEL SYSTEM DDDDDP Fuel System The Vision s fuel tank is mounted in the rear overhang between the frame rails and is made of 12 gauge HRLCCQ T125 aluminized steel The fuel system meets the requirements of Federal Motor Vehicle Safety Standard FMVSS 301 Fuel Systems Integrity For School Buses Observe all safety and environmental warnings and precautions in the Introduc tion chapter of this manual before performing any of the tests and maintenance pro cedures in the section CEN Blue Bird does not approve or disapprove additions to or modi fications of Blue Bird fuel systems Blue Bird fuel systems are designed and in stalled to meet federal standards and engine manufacturer s guidelines The upfitter or modifier assumes all responsibility for vehicle engine and fuel sys tem if the fuel system is changed or modified All fuel system components must be a minimum of 7 from any exhaust sys tem component unless properly shielded The system includes a flush mounted inspection plate over the sending unit mount ed in the bus floor and covered with floor covering material This inspection plate is located near the centerline of the bus and approximately inline with the filler tube neck at the fuel door The system is designed with either 60 or 100 gallons fuel capacity depending upon wheelbase The fuel tank is equipped with a inch NPT plug in the bottom This plug must be removed periodically to allow collected water and sedim
8. appropriate fuel tank opening Tighten the fitting finger tight Then apply a bead of Perma Lok LH 150 or equivalent thread sealant around the exposed threads and tighten 2 turns further using an appropri ate open end wrench Orient the flange thread toward the outboard edge of the fuel tank and in the direction the filler tube runs 7 Install the 45 elbow vent fitting finger tight into Overflow the appropriate opening in the fuel tank Apply a ko Supply bead of Perma Lok LH 150 or equivalent thread sealant around the exposed threads Tighten 2 turns further using an appropriate open end wrench Ori ent the flange thread toward the outboard edge of the fuel tank and in the direction the filler tube runs 8 Install the tubing adapter into the 45 elbow vent fitting Tighten finger tight Apply a bead of thread sealant Perma Lok LH 150 and tighten 1 1 2 flats further BLUE BIRD VISION SERVICE MANUAL 634 0 BLUE BIRD Fuel Tank Installation Installation of the fuel tank is accomplished in the reverse order of the removal in structions above 1 Position the fuel tank on the tank supports CAN Ensure there is protective webbing between the straps and the fuel tank and between the fuel tank and the support members There must be no metal to metal contact 2 Loosely attach one end of the tank tie down straps 3 Wrap the tie down straps over the fuel tank and loosely install the other s
9. call for low idle and a 75 pulse wave as full RPM During the normal use cycling of the accelerator pedal the ECM adjusts its calibration resulting in a broader duty cycle range in which 10 22 signals idle and 75 90 signals full RPM This process results in a slight but noticable change in the throttle pedals sensi tivity until the auto calibration is completed During this time the Driver may notice that full RPM is achieved before the pedal is fully depressed and or that more pedal movement is required to raise engine RPM above idle This condition is normal during the power up and auto calibration period Testing And Troubleshooting Caterpillar Breakout The acellerator installed on the Blue Bird Vision produces a signal which meets Caterpillar s specs for PWM input throttle signal Caterpillar provides diagnostic tests and codes in their ET and PocketTech diagnostic software The output of the throttle assembly may also be tested using a multimeter which is capable of measuring a PWM duty cycle as follows 1 Inspect all electrical connectors and wiring harness associated with the ac L cellerator 63 7 2 With the ignition off disconnect the Deutsch electrical Breakout Lead plugged inline between ends of position sensor s Deutsch connector connector located just above the accelerator pedal 3 Turn the ignition on and and check for voltage from terminal A of the vehicle wiring harness to vehicle
10. ent to drain When the discharge is clean fuel replace the plug Wheel Base Gallons Liters 189 inches 60 227 12 217 inches 60 227 12 238 inches 60 227 12 252 inches 100 378 54 273 inches 100 378 54 All fuel system lines and components must be secured a minimum of 7 inches 178 mm from any exhaust component Do not repair a damaged fuel line replace it The number of clamps required to secure the fuel lines is dependent upon the wheelbase of the bus When removing a clamp ensure it is replaced in the proper position Check with your Blue Bird Dis tributor for replacement fuel lines Wheelbase Number of Clamps 189 6 217 7 238 8 252 8 273 9 In 2007 diesel en gines use only diesel fuel labeled Ultra Low Sulfer per the engine manufacturer s specifications In Caterpillar use oils meeting API CJ 4 or Caterpillar ECF 3 compliant See Caterpillar Opera tion and Maintenance Manual SEBU8083 08 for details In Cummins use oils meeting API CJ 4 SL and Cummins Engine Standard CES 20081 See Cum mins Owners Manual ISB 6 7L CM2150 for details 625 0 BLUE BIRD 0 VISION SERVICE MANUAL Drain Tank Vent Fill Vent Fuel Sender L Not Used Supply 60 Gallon Fitting Placement Detail Fuse TankVent Fuse rN ae Plug Fuel Sender 100 Gallon Fitting Placement Detail Hold fitting with wrench adjacent to fittings being installed to engine
11. ide 4 Ensure the tank is properly oriented The front is the end of the tank with the hose fittings 5 Position the front tank guard and install it to the front tank support Torque 3 bolts 200 to 36 52 Ft Ib 48 81 70 50 Nm Use new lock nuts 6 Position the rear tank guard and install it to the rear tank support Torque to 36 52 Ft lb 48 81 70 50 Nm Use new lock nuts Position the fuel tank beneath the chassis Raise the tank to a level where it is possible to install the fuel lines and wiring Clean sender wiring termi nals prior to assembly Protect the sender terminals with heavy grease 9 Torque hose clamps to 45 In Ib 5 08 Nm Worm gears and drive hex or slot should be oriented toward the top for accessibility 10 Lift the fuel tank into position 11 Install the 4 bolts in the front tank guard Use a flat washer on each side of the installation Use a new locknut Torque to 36 52 Ft Ib 48 81 70 50 Nm 12 Install the 4 bolts in the rear tank guard Use a flat washer on each side of the installation Use a new locknut Torque to 36 52 Ft lb 48 81 70 50 Nm 13 Install the 2 bolts at each end of each tank support Use a flat washer at each side of the installation Use new locknuts Torque to 40 58 Ft Ib 54 25 78 64 Nm 14 Ensure the fuel tank is centered front to rear and side to side 15 Tighten the first nut on each tank strap to 40 Ft Ib 54 23 Nm Then while holding the first nut torque the jam nut to 40 Ft Ib 54 23
12. ing unit P Connect the negative lead to the outer terminal 4 Turn on the multimeter and note the resistance If the tank is full the resistance should be approximately 85 90 ohms To further test the sending unit with it removed from the tank 1 Remove the screws securing the access plate Remove the plate H 4 OHMS 2 Disconnect all wires from the sending unit 3 Remove the five hex held bolts which secure the sending unit to the tank Remove the sending unit being careful to avoid damaging the gasket 4 Set the multimeter to read ohms Connect the positive test lead to the terminal in the center of the sending unit Connect the negative lead to the outer terminal 5 Hold the sending unit with its mounting plate parallel to the floor and the float arm hanging free in the empty position Turn on the multimeter and note the resistance With the arm in the lowered empty position the resistance should be approximately 0 3 Ohms 6 Slowly raise the float arm The resistance should increase proportionally to the movement of the arm until it reaches 85 90 Ohms at the fully raised full position If the reading is out of range intermittent or sporadic replace the sending unit 0 BLUE BIRD C O BIRD Fuel Tank amp Barrier Locate in front set of holes on 60 gallon fuel tank Locate in front amp rear sets of holes on 100 gallon fuel tank 2 va Fasteners thru front two holes 60 gallon fuel tank only
13. km or 1 100 gallons 4150 L of fuel consumption or 250 hours of engine operation or 6 months whichever is the first to occur The spin on filter cartridge replacement is R90 BB 02 This is a 30 micron PRIMARY filter therefore secondary final filtration is required before the fuel reaches the engine The filter cartridge must be replaced immediately to avoid contamination of the fuel system Contaminated fuel may make it nec essary to change this filter cartridge at any time not only at scheduled intervals The secondary fuel filter is located on the left hand driver s side of the engine on a mounting bracket just behind the air compressor This filter must be changed on the PM Level 1 schedule as well Just one tank of contaminated fuel can cause this filter to need change without regard to the schedule The secondary fuel filter is also a spin on canister type filter car tridge that requires periodic maintenance The replacement filter car tridge Blue Bird Part Number 0060586 must be replaced periodically The Level 1 Preventive Maintenance Schedule established by Caterpillar dictates this period This interval is 11 000 miles 17 700km or 1 100 gallons 4150 L of fuel consumption or 250 hours of engine operation or 6 months whichever is the first to occur See appropriate Caterpillar publication for details The new spin on filter should not be filled with fuel This could introduce contaminants into the engine Prime the fuel sy
14. provides the engine an analog signal instructing it to increase or decrease RPM based on the position of the accelerator This is done with a three wire potentiometer The sensor is provided a continuous 5V DC pin B27 and a ground pin B28 by the engine ECU As the accelerator pedal is depressed the throttle position sensor will relay its position to the engine pin B35 The throttle position sensor can be tested by the following Disconnect sensor plug and meassure resistance on accelerator side of connec tor between e Pins Cand A Supply and Return Value should be between 2000 and 3000 ohms e Pins C and B Supply and Return Released pedal value should be between 1500 and 3000 ohms e Pins C and B Supply and Return Depressed pedal value should be between 200 and 1500 ohms Resistance should decrease proportionally as pedal is depressed Released pedal resistance minus depressed pedal resistancemust be greater than 1000 ohms TID Do not attempt to adjust or repair throttle position sensor or idle validation sensor Warranty will be voided Should the accelerator fail to meet specifications the entire pedal must be re placed c5 C701 Engine Harness THROTTLE RETURN ua f sm 27 Ke a THROTTLE SIGNAL 1 AC ETSER ZABRON REZA BROUN ie res hee om lt lt lt herrea DA Throttle Sensor 1 Driver s Control Module THROTTLE POWER co O A a E SENSOR POWER ALSAM KER ronn Ao THROTTLE SIGNAL 2 MASUM gt E CRAY e
15. stem in accordance with instructions in the Caterpillar Operation and Maintenance Manual Fuel Level Sending Unit The Fuel Level Sending Unit is mounted in the top of the fuel tank An access plate located in the floor center aisle provides access to the sending unit for testing and replacement An electrical terminal in the top center of the sending unit receives signal voltage from the instrument cluster A ground terminal near the outer edge of the sender connects to ground via the chassis harness The signal current passes through a me chanical variable resistor which is actuated by the sender s float arm As the float rises and falls with the level of fuel in the tank it varies the resistance of the unit from 0 3 ohms when the float arm is at its lowest empty tank to 85 90 when the arm is fully raised full tank This resistance is monitored by the control module of the in strument cluster which registers it as a percentage and passes it to the fuel gauge Testing the Fuel Level Sending Unit A multimeter may be used to check the resistance of the sending unit If the actual fuel level is known the sender may be tested witout removing it from the fuel tank 1 Inside the bus remove the screws securing the access plate Remove the plate 2 Disconnect all wires from the sending unit 3 Set the multimeter to measure ohms Connect the positive 5 95 OHM test lead to the terminal in the center of the send
16. tes an output signal which communicates the throttle position back to the ECM The output signal conveys its data by means of pulse width modulation PMW a method by which the wave form of a pulsating DC current signal may be altered in order to convey a signal Because of its fundamentally on off nature square wave form PWM is particularly well suited for communication between digital control devices and microprocessors Pulse Width Modulation Pulse width modulation varies the width of the positive crest of each wave of cur rent Thus in pulse width modulation both the voltage amplitude and wave length frequency remain constant while the duration of the positive pulse pulse width varies The longer the duration of the pulse the higher the percentage of the total wave length it occupies For this reason pulse width is measured as a percentage of the wavelength The percentage is refered to as the duty cycle In typical applications the signal frequency is quite higher than the response rate of the load device The on off pulses therefore tend to be smoothed out or averaged over time while the load operates The net result is the appearance and be havior of varying output voltage even though the voltage of the pulses is constant Throttle Control Accelerator Pedal Assembly Throttle Position Sensor Deutsch Connector Located just above the accelerator position sensor BLUE BIRD VISION SERVICE MANU
17. the Accelerator Pedal Assembly read ings should be Idle lt 10 Full Throttle 290 If duty cycle values are determined to be out of range re place the accelerator position sensor and or the accelera tor pedal assembly Slowly move the accelerator pedal from idle to full throttle position while observing the meter Duty Cycle percentage should increase and decrease proportionally to the move ment of the pedal If it does not replace the accelerator position sensor and or the accelerator pedal assembly Throttle Position Sensor SENSOR SWITCH COMMON ACCELEARATOR PEDAL POSITION SUPPLY VOLTAGE 8 VOLTS Pedal Fully De Red lead connected to Meter set to display white PWM signal wire Duty yde 6 Drivers Control Module Pedal at Idle C701 C7 Engine Harness C800 Engine Harness ERTO SENSOR SWITCH COMMON D eh BROWN ACCELEARATOR PEDAL POSITION Dal BLUE De SUPPLY VOLTAGE 8 VOLTS Testing And Troubleshooting Cummins The Cummins accelerator pedal incorporates two Throttle Position Sensors to pro vide the required input to the engine ECM These components are non serviceable and should not be removed from the accelerator assembly or you could risk voiding the warranty Each component has three wires going through a weather pak con nector and can be tested individually for proper operation Throttle Position Sensor Coil Resistance The Throttle Position Sensor
18. vent con tamination 8 Remove the sender wiring Filler Neck Filler Tube Shield 6 Hexhead Screws Frame Rail 4 Bolts NS SS Tank Guard Assembly of New Fuel Tank 2 bolts each end 1 Position the new fuel tank on the support rails 2 Install the tie down straps QUEL Ensure there is protective webbing between the straps and the fuel tank and between the fuel tank and the support members There must be no metal to metal contact 3 Install overflow fitting in 2 places Tighten the fittings finger tight then apply a bead of Perma Lok LH 150 or equivalent thread sealant around the ex posed threads Then tighten 2 turns further using an appropriate open end wrench Do not use an adjustable wrench Ensure the barbs of the fittings are directed at the nearest edge of the fuel tank and in the direction of the filler tube 4 Install an 18 20 inch 458 508 mm length of tub ing to direct fuel overflow past the frame rail 5 Install the return line 90 fitting finger tight at the appropriate opening Tighten the fitting finger tight and then apply a bead of Perma Lok LH 150 or equivalent thread sealant around the exposed threads Then tighten 2 turns further using an appro priate open end wrench Orient the flange thread toward the outboard edge of the fuel tank and in the direction the filler tube runs 6 Install the supply line 90 fitting at the
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