Fuel Injection System - Dual Unit Tbi Chevrolet Camaro II

COMPONENT TESTING

Note. Specific component testing information not available. Refer to any tests performed during REMOVAL & INSTALLATION or OVERHAUL procedures

APPLICATION

ROCHESTER THROTTLE BODY NO.

IDENTIFICATION

The throttle body identification number is "roll-stamped" on the front mounting flange on the throttle lever side of the throttle body. (Scheme 35) Code letters are stamped on the throttle body at external tube locations to identify vacuum hose connections.

Throttle Body Identification Location This number should be used for service information. Scheme 35

DESCRIPTION

The General Motors dual unit (cross-fire) Electronic Fuel Injection (EFI) system consists of 9 major sub-assemblies: fuel supply system, Throttle Body Injector (TBI) assembly, Idle Air Control (IAC) system, Electronic Control Module (ECM), Electronic Spark Timing (EST), Electronic Spark Control (ESC), Hood Louver Control (HLC), data sensors and emission controls.

Fuel is supplied to engine through electronically pulsed (timed) injector valves located in separate throttle bodies on top of intake manifold (1 for each bank). Each throttle body unit is a Model 400 unit. The ECM controls amount of fuel metered through injector valves based upon engine demand and efficiency information. The ECM is a digital electronic computer which receives and computes signals from various data sensors.

Note. Primary sub-systems which affect fuel system operation will be covered in this article: fuel supply system, TBI assembly, IAC system, ECM, HLC and data sensors. Because of the interrelated functions of the Computer Command Control (CCC) system (the ECM is the "brain"), see appropriate COMPUTER COMMAND CONTROL article in ENGINE PERFORMANCE section for more information.

FUEL SUPPLY SYSTEM

An electric fuel pump (located inside fuel tank as an integral part of fuel gauge sending unit) supplies fuel under pressure to fuel pressure accumulator on front TBI unit. From the accumulator, fuel enters the pressure regulator on rear TBI unit. A fuel pump relay (located on left side of engine compartment) controls fuel pump operation.

When ignition switch is turned on, fuel pump relay activates fuel pump for 1 1/2-2 seconds to prime the injectors. If ECM does not receive reference pulses from the distributor after this period, it deactivates fuel pump circuit. The fuel pump circuit will be activated again through the relay when ECM receives distributor reference pulses.

Note. Power to relay from battery is provided when oil pressure is above 4 psi (.3 kg/cm 2 ). If pump relay malfunctions, engine could still be started after oil pressure has reached 4 psi (.3 kg/cm 2 ).

THROTTLE BODY INJECTOR (TBI) ASSEMBLIES

Each TBI assembly is composed of 2 castings: a throttle body with a valve to control air flow, and a fuel body with an integral pressure regulator (rear unit) or accumulator (front unit) and fuel injector. Throttle body casting may contain ports to generate vacuum signals for EGR valve, MAP sensor and canister purge system.

Fuel pressure is regulated by the pressure regulator. The regulator is a diaphragm-operated relief valve. Fuel pressure is regulated by balancing circulating fuel flow on one side of diaphragm assembly and calibrated regulator spring on other side. Pressure regulator maintains a constant pressure drop of about 10 psi (.7 kg/cm 2 ) across both injectors throughout all engine operating conditions by controlling return of excess fuel to fuel tank. (Scheme 36)

The accumulator is of similar design as pressure regulator. It makes up for momentary fuel pressure drop between front and rear TBI units (due to injector openings). The accumulator maintains consistent operating pressures.

Each fuel injector is a solenoid-operated device controlled by ECM. Fuel is supplied at lower end of injector by fuel supply system. ECM activates solenoid which lifts a normally closed ball valve off its seat. Fuel under pressure is injected in a conical spray pattern at throttle bore walls above throttle valve. Excess fuel passes through accumulator of front unit, to pressure regulator of rear unit and is returned to tank.

Sectional View of Throttle Body Assemblies Both units are Model 400 units. Scheme 36

IDLE AIR CONTROL (IAC) SYSTEM

The IAC system consists of an electrically controlled motor which positions IAC valve in air by-pass channel around throttle plate of each TBI unit. The IAC valve is a part of the throttle body casting. The ECM calculates desired position of each IAC valve based upon battery voltage, coolant temperature, engine load and engine speed. It controls idle speed while preventing stalls due to engine load changes.

If engine speed is lower than desired, ECM activates motor to retract IAC valve. When IAC valve is retracted, more air is diverted around throttle plate, increasing engine speed. If engine speed is higher than desired, ECM activates motor to extend IAC valve. When IAC valve is extended, less air is diverted around throttle plate decreasing engine speed. If engine speed falls below a preset speed and the throttle plate is closed, ECM senses a near stall condition. To prevent stalling, ECM will calculate an IAC valve position based upon barometric pressure.

ELECTRONIC CONTROL MODULE (ECM)

The ECM is located behind instrument panel and is the "brain" of EFI and Computer Command Control systems. Information from all data sensors is received and processed by the ECM to produce proper pulse duration for each injector, correct idle speed and proper spark timing. The ECM performs calculations to control the following EFI operating conditions: engine start, engine flooding, engine running, fuel enrichment during acceleration, lean fuel mixture during deceleration, fuel cutoff and battery voltage correction.

During engine starts, the first signal sent to injectors is a "prime" pulse. This pulse charges intake manifold with fuel during or just prior to engine starting. This pulse width (injector "on" time) is not synchronized with HEI distributor reference pulses. Prime pulses will be delivered for a length of time dependent upon coolant temperature.

After delivering prime pulses, ECM will deliver a pulse for each distributor reference pulse received. Air/fuel ratio is determined by ECM based upon throttle position and coolant temperature. The lower the coolant temperature, the longer the injector pulse width (richer air/fuel ratio). The higher the coolant temperature, the shorter the injector pulse width (leaner air/fuel ratio).

During engine flooding, accelerator pedal must be depressed enough to set wide open throttle position. At this position, ECM calculates injector pulse width equal to an air/fuel ratio of 20:1. This air/fuel ratio will be maintained as long as throttle remains wide open and engine speed is below 600 RPM. If throttle position becomes less than 80 percent and/or engine speed exceeds 600 RPM, ECM changes injector pulse width to that used during engine starting (based upon coolant temperature and manifold vacuum).

When engine is running above 600 RPM, ECM operates in open loop mode. In open loop, ECM calculates injector pulse width based upon coolant temperature and manifold absolute pressure (MAP). Engine will remain in open loop operation until oxygen sensor reaches operating temperature, coolant temperature reaches a preset temperature and a specific period of time elapses after engine start. When all these conditions are met, ECM operates in closed loop mode. In closed loop, ECM controls injector pulse width according to oxygen sensor signals, maintaining air/fuel ratio of 14.7:1. In either mode, injectors are pulsed alternately for each distributor reference pulse.

Fuel enrichment during acceleration is provided by ECM. Sudden opening of throttle plates causes a rapid increase in MAP. Pulse width is directly equal to MAP, throttle position and coolant temperature. The higher the MAP and wider the throttle angle, the wider the pulse width (richer mixture). During enrichment, injector pulses are not in proportion with distributor reference signals. Any reduction in throttle angle will cancel fuel enrichment.

During normal deceleration, air/fuel mixture must be leaner. ECM calculates injector pulse width similar to that during fuel enrichment. Fuel output is reduced due to fuel remaining in the intake manifold. During sudden deceleration, when MAP, throttle position and engine speed are at preset levels, fuel flow is cut off completely to remove fuel from the engine. This deceleration fuel cutoff overrides normal deceleration mode. During either deceleration mode, injector pulses are not in proportion to distributor reference signals.

Battery voltage corrections by ECM are performed during all operating modes of EFI system. As battery voltage decreases, ECM increases injector pulse width with a correction factor stored in ECM's memory.

Hood Louver Control (HLC) system is controlled by ECM. When engine coolant temperature and throttle position meet preset specifications, ECM activates HLC relay which opens hood louver to allow additional air into engine.

DATA SENSORS

Each sensor furnishes an electrical signal to ECM, modifying injector pulse to conform to engine operating conditions. These sensors are as follows

Coolant Temperature Sensor (CTS)

The CTS is located in thermostat housing. This sensor is a variable resistance type which transmits an electrical signal (proportionate to engine temperature) to the ECM.

Oxygen Sensor

Oxygen sensor is mounted in exhaust manifold, directly behind cross-over pipe. This sensor is similar to a small battery. Voltage output of sensor indicates to ECM the amount of oxygen in exhaust gases. ECM corrects air/fuel ratio (according to signals received by oxygen sensor) only when system is operating in closed loop.

Manifold Absolute Pressure (MAP) Sensor

The MAP sensor is mounted on left side of engine compartment. This sensor is a variable resistance type which has a vacuum hose connected to throttle body. The sensor monitors changes in intake manifold pressure which result from engine load and speed changes. As MAP changes, electrical resistance of sensor changes. ECM uses resistance value of sensor to control injector pulse width.

Vehicle Speed Sensor (VSS)

The VSS is mounted behind speedometer in instrument cluster. This sensor provides ECM with pulses to determine vehicle speed. This information is used by ECM to control IAC system.

Note. Vehicle should not be driven without VSS installed or speedometer cable disconnected.

Throttle Position Sensor (TPS)

TPS is mounted on side of rear throttle body and is connected to throttle shaft. A throttle rod connects both front and rear throttle body units to ensure throttle valve of each unit is positioned the same. This sensor converts throttle angle to an electrical signal for use by ECM to determine engine fuel requirements.

Note. The throttle rod end bearing is permanently attached to throttle lever stud of rear unit. Throttle rod must not be removed from rear unit. If throttle rod bearing needs replacement, rear throttle body unit must be replaced.

Engine RPM Reference

The "R" terminal of the HEI distributor module is used to send engine RPM signals to ECM.

Note. More sensors are used by ECM to control engine performance and other systems. See appropriate COMPUTER COMMAND CONTROL article in ENGINE PERFORMANCE section for more information.

PRELIMINARY CHECKS

The following systems and components must be in good condition and operating properly before beginning diagnosis of the fuel injection system

1. All support systems and wiring.
2. Battery connections and specific gravity.
3. Ignition system.
4. Compression pressure.
5. Fuel supply system pressure and flow.
6. All electrical connections and terminals.
7. Vacuum line, fuel hose and pipe connections.

Note. Trouble shooting and diagnosis of fuel system should begin with determining fuel system pressure. Before performing any test on the fuel system, pressure must be released from the system.

FUEL SYSTEM PRESSURE TEST

1. Remove "FUEL PUMP" fuse from fuse block in passenger compartment. Crank engine. Engine will start and run until fuel supply remaining in fuel lines is used. Engage starter again for about 3 seconds to ensure all fuel is out of lines. Turn ignition off and replace fuse.
2. Remove air cleaner and plug thermal vacuum port on throttle body. Remove steel fuel line between front and rear throttle body units. When removing fuel line, always use 2 wrenches. Install a fuel pressure gauge (J-29658 or equivalent) between throttle body units.
3. Start car and observe fuel pressure reading. Use Fuel System Diagnosis chart if pressure is not between 9-13 psi (.6-.9 kg/cm 2 ). Use Injector System Diagnosis chart if pressure is between 9-13 psi (.6-.9 kg/cm 2 ).
4. Depressurize fuel system as described in step 1). Remove fuel pressure gauge and reinstall steel line between throttle bodies. Start car and watch for leaks. Remove plug from throttle body thermal vacuum port and reinstall air cleaner.

HESITATES, SLUGGISH, SAGS OR POOR MILEAGE

1. Visually check MAP hose for leaks or restriction and TPS for sticking or binding. Check for air leaks around throttle body mounting and intake manifold. Ensure fuel pressure is steady 9-13 psi (.6-.9 kg/cm 2 ) at all operating ranges. Ensure base timing is correct.
2. With injector connectors disconnected, check for fuel leakage from injectors while cranking. Check for open HEI ground (circuit 453). Check fuel injector fuel filters for blockage. Check TBI balance adjustment. See appropriate article in TUNE-UP section.
3. Check A/C compressor control and torque converter clutch (TCC) system. See appropriate COMPUTER COMMAND CONTROL in ENGINE PERFORMANCE section for testing procedures.

CUTS OUT OR STALLS

1. Check for intermittent open or short to ground in the following circuits: 5-volt reference (416), HEI reference (430), fuel pump circuit (120), injector drive circuits (467 and 468), IAC drive circuits (441, 442, 443 or 444).
2. Check for restricted fuel filter. Ensure fuel pressure is 9-13 psi (.6-.9 kg/cm 2 ) at all operating ranges. Inspect fuel injector "O" rings for damage. Ensure steel back-up washer is located beneath large "O" ring of each injector.

SURGE

Check for intermittent open or short to ground in the following circuits: transmission converter clutch (420 and 422), HEI by-pass (424), EST (423). Perform EGR diagnosis. Refer to CCC SYSTEM in Computerized Engine Controls section for testing procedures.

HARD STARTING (HOT OR COLD)

1. Check for high resistance in coolant sensor circuit. Visually check TPS for sticking or binding. Ensure fuel pressure is 9-13 psi (.6-.9 kg/cm 2 ) at all operating ranges.
2. Check fuel pump relay. Disconnect oil pressure switch. If engine cranks but will not start, perform fuel system diagnosis (at point where fuel pump fuse proves okay).
3. Check injectors. With injector harness connectors disconnected, check for fuel leakage while cranking.
4. Check cranking circuit. Refer to COMPUTER COMMAND CONTROL in Computerized Engine Controls section for testing procedure.

Fuel System Diagnosis. Scheme 37

This procedure assumes that the "CHECK ENGINE" light is functioning and is "ON".

Injector System Diagnosis. Scheme 38

Note. Location of ECM varies between model application. ECM is located under instrument panel.

Removal & Installation

Disconnect negative battery cable. Disconnect 2 electrical connectors from ECM. Remove ECM mounting hardware and ECM. To install, reverse removal procedure.

Fuel pump relay is located in engine compartment, on firewall near left fender panel. Remove electrical connector, mounting screws and relay. To install, reverse removal procedure.

MAP sensor is located in engine compartment, on firewall near left fender panel on all models. Remove vacuum hose, mounting screws and MAP sensor. To install, reverse removal procedure.

Remove instrument cluster and speedometer assembly. Disconnect VSS from speedometer. Disconnect VSS electrical connector and remove VSS. To install, reverse removal procedure.

Disconnect electrical connector and remove CTS. To install, reverse removal procedure. Handle CTS with care to prevent damage to sensor calibration.

Note. Oxygen sensor may be difficult to remove when engine temperature is below 120°F (48°C). Excessive force may damage threads.

Disconnect electrical connector. DO NOT attempt to remove single wire from oxygen sensor. Carefully back sensor out of cross-over pipe. Handle sensor with care and do not allow dirt or other foreign matter to contact louvered end of sensor. To install, reverse removal procedure.

Note. Before installing a used sensor, coat threads with liquid graphite compound containing glass beads (special anti-seize compound).

Removal

1. Remove fuel tank filler cap and drain tank. Raise vehicle on hoist. Disconnect exhaust pipe at converter and rear hanger. Allow exhaust system to hang over axle assembly.
2. Remove tail pipe and muffler heat shields. Remove fuel filler neck heat shield located behind left rear tire. Remove rear suspension track bar and brace. Disconnect fuel pump gauge electrical connector at body harness connector. NOTE: DO NOT disconnect fuel pump electrical connector at fuel pump. Wiring harness is permanent part of pump. DO NOT pry up on cover connector.
3. Remove pressure from fuel lines as described under Fuel Pump Pressure Test. Remove fuel lines. Remove fuel line retaining bracket on left side and brake line clip from bracket. Position support jack under axle assembly.
4. Disconnect lower ends of shock absorbers. Lower axle assembly. Remove both coil springs. Remove fuel tank straps. Lower rear suspension as far as possible without damaging brake lines. Remove tank by rotating front of tank down and sliding to right. Remove fuel pump attaching screws and fuel pump.

Installation

To install, reverse removal procedure.

1. Relieve pressure from fuel lines as explained under Fuel Pump Pressure Test. Remove air cleaner. Disconnect electrical connectors from injectors, IAC motors and TPS. Disconnect and identify all vacuum lines.
2. Remove throttle cable and transmission detent cable. Remove throttle rod from between front and rear throttle body units. DO NOT attempt to remove rod at rear throttle body unit. Throttle rod bearing is permanently attached to rear throttle lever stud. Remove cruise control cable (if equipped).
3. Disconnect fuel lines from each throttle body unit using 2 wrenches. Remove throttle body-to-manifold bolts. Remove each throttle body unit as an assembly.
4. If manifold cover or either throttle body requires replacement, do the following: If equipped, remove throttle stop screw plugs. Using a prick punch, mark location over center line of throttle stop screw to drill a hole.
5. Using a 5/32" drill, drill a hole through throttle body casting to hardened steel plug. Using a 1/16" punch, drive through bottom of drilled hole and knock out plug.
6. If throttle synchronizing screw has a spot-welded retaining collar to seal factory setting, grind off weld. Block throttle lever movement, relieving spring force against throttle synchronizing screw, to prevent damage to screw during removal and installation.
7. Remove screw and collar. Discard collar. Reinstall screw and remove blocking from throttle lever.

To install, reverse removal procedure and note the following: Install front throttle body first. Ensure throttle body assemblies and intake manifold sealing surfaces are clean. Always use new throttle body-to-manifold gaskets. Perform preliminary throttle valve synchronization adjustment. See Adjustments.

Note. Throttle body units must be installed in original position. DO NOT interchange front and rear units. After installation, minimum idle speed, throttle valve synchronization and throttle rod alignment must be checked and adjusted as required.

ADJUSTMENTS

Note. For all on-vehicle adjustments not covered in this article, see appropriate TUNE-UP article.

Note. The following procedure applies only if manifold cover, 1 or both throttle body units, or throttle body castings have been replaced.

Scheme 39

1. With throttle body units properly installed, turn throttle stop screws of both units counterclockwise. Turn enough to break contact between screws and throttle lever tangs.
2. Adjust each screw to allow both throttle valves to close. Throttle rod end bearing will move freely on front unit throttle lever stud when both valves are closed.
3. Turn front unit throttle stop screw clockwise until it contacts lever tang. Turn 1/4 additional turn. Turn rear unit throttle stop screw clockwise until it contacts tang. Turn 1/2 additional turn. Perform final throttle valve synchronization on-vehicle with engine running. See "Fuel Injected Idle Speed (5.0L Engine)" in appropriate TUNE-UP article.
4. After performing idle speed adjustment, check throttle rod alignment. Push rear unit throttle lever to position both front and rear units in wide open throttle position. Push throttle valves in direction of arrows. Move throttle rod and bearing assembly toward front unit casting boss. (Scheme 37) (Scheme 39): Throttle Rod Adjustment This adjustment is performed after replacement of throttle body or manifold cover.
5. Turn front unit throttle stop screw clockwise until it contacts lever tang. Turn 1/4 additional turn. Turn rear unit throttle stop screw clockwise until it contacts tang. Turn 1/2 additional turn. Perform final throttle valve synchronization on-vehicle with engine running. See "Fuel Injected Idle Speed (5.0L Engine)" in appropriate TUNE-UP article.
6. Measure clearance at outside edge of throttle rod and bearing assembly on front unit. Clearance must not exceed.20" (5 mm) maximum. (Scheme 37) If greater, replacement item must be exchanged and adjustment procedure repeated. If correct, install new throttle rod and bearing assembly retaining clip.
7. Move both throttle levers through total travel and fully close throttle valves. Push throttle levers in direction of arrows. Measure clearance at inside edge of throttle rod and bearing assembly on front unit. Clearance must be.04" (1.02 mm) minimum. (Scheme 37)
8. If clearance is less than specified, remove throttle rod and bearing assembly retaining clip. Exchange replacement assembly and perform adjustment procedure again. After obtaining all adjustment specifications, install air cleaner and ensure no binding is present in accelerator and throttle linkages.

DISASSEMBLY

Note. Before performing any service on throttle body assembly, it is essential that throttle body be placed on a HOLDING FIXTURE (J-9789-118, BT 30-15 or equivalent) to prevent damage to throttle valve. Disassembly of each throttle body unit is the same. DO NOT interchange components between front and rear units. Mark and identify each component for identification.

Fuel Meter Cover

1. Remove 5 cover-to-meter body screws and lock washers. Lift off fuel meter cover with fuel pressure regulator assembly (rear unit) or accumulator assembly (front unit) attached. DO NOT remove fuel meter cover gasket at this time. (Scheme 38) WARNING: DO NOT remove 4 screws attaching pressure regulator (accumulator) to fuel meter cover. The regulator (accumulator) includes a spring under heavy tension which may cause personal injury if released. Fuel meter cover and pressure regulator (accumulator) are serviced as an assembly only. DO NOT immerse assembly in any type of cleaning solvent.
2. Remove fuel pressure regulator (rear unit) or accumulator (front unit) dust seal from fuel meter body.

Fuel Meter Cover Assembly Removal Do not remove fuel meter cover gasket at this time. Scheme 40

Fuel Injector

1. With fuel meter cover gasket in place, use a screwdriver to carefully pry the injector from the fuel metering body. Carefully lift injector out with a twisting motion. Remove fuel meter cover gasket. (Scheme 39) NOTE: Use care in removing injector to prevent damage to electrical connectors, fuel filter and nozzle. Injector is serviced as complete assembly only. Injectors are not interchangeable between front and rear units.
2. Carefully rotate injector filter back and forth to remove from base on injector. Remove large "O" ring and steel back-up washer on top of injector cavity in fuel meter body. Remove small "O" ring at bottom of injector cavity.

Fuel Injector Assembly Removal Keep fuel meter cover gasket in place until injector is removed to prevent damage to casting. Scheme 41

Fuel Meter Body

Remove fuel inlet and outlet nuts and gaskets from fuel meter body. Remove air cleaner stud (if equipped). Remove 3 fuel meter body-to-throttle body screws and lock washers. Remove fuel meter body and gasket.

Throttle Body

1. Disassembly of throttle body unit for immersion in cleaning solvent requires removal of TPS (rear unit) and IAC assemblies. Throttle valve screws are staked in position and should not be removed. If necessary to remove TPS, continue as follows
2. Invert throttle body assembly and place on clean, flat surface. Remove and discard TPS attaching screws. Remove lock washers, retainers and TPS from throttle body. (Scheme 40)
3. If necessary, remove TPS actuator lever-to-throttle shaft screw. Remove IAC assembly and gasket from each throttle body. Remove and discard IAC gaskets.

TPS Assembly Removal (Rear Unit Only) Invert throttle body to remove TPS. Scheme 42

CLEANING & INSPECTION

1. Clean all metal parts in a cold immersion-type cleaner and blow dry with compressed air.
2. DO NOT immerse TPS, IAC, fuel meter cover and pressure regulator (accumulator) assembly, fuel injector, fuel filter, rubber parts and diaphragms in cleaner.
3. Inspect mating surfaces for damage that may prevent gasket sealing. Repair or replace components which may be cause of problems listed under Trouble Shooting and Diagnosis.

Place throttle body on holding fixture. Install IAC assembly with new gasket. Tighten securely. Install TPS actuator lever by aligning flats on lever with flats on end of shaft. DO NOT install TPS until complete assembly of rear throttle body assembly.

Note. Before installing IAC assembly, measure distance that valve extends from motor housing. Measuring from end of housing to end of cone, distance should not exceed 1 1/8" (28 mm). If not to specification, push pintle inward (IAC valve with collar on electrical connector) or compress pintle retaining spring toward IAC body while turning pintle inward with a clockwise motion (IAC valve without collar on connector). On IAC valves without collar, return spring to original position with straight portion of spring end aligned with flat surface under pintle head.

1. Install fuel meter body gasket on throttle body. Cutout portions of gasket must match cutouts on throttle body. Install fuel meter body on gasket.
2. Apply thread locking compound (supplied in service kit) on 3 attaching screws. Install lock washers and screws. Tighten screws. Install fuel inlet and outlet nuts with new gaskets.

1. Using a slight twisting motion, install fuel injector filter on nozzle end of injector until seated against injector base. NOTE: Filter is cone-shaped. Large end of filter points up toward injector electrical connectors. Filter should cover raised rib at base of injector.
2. Lubricate "O" rings with automatic transmission fluid. Push small "O" ring on nozzle end of injector until seated against injector fuel filter. Install steel back-up washer in recess in injector cavity of fuel meter body.
3. Install large "O" ring directly above back-up washer. Press "O" ring down in cavity recess until flush with top of fuel meter body casting surface. (Scheme 41) NOTE: "O" rings and back-up washer must be installed in this manner. DO NOT attempt to seat "O" rings and washer after injector is placed in cavity.
4. Using a pushing/twisting motion, install injector in cavity. Align raised lug on injector base with notch in fuel meter body. Push down on injector to center "O" ring in bottom of cavity and to seat injector.
5. Injector is correctly installed when lug on injector is seated in fuel meter body notch and electrical connections are parallel to throttle shaft in throttle body.

Note. Insure injectors and components are installed in their original throttle body. DO NOT interchange components between front and rear units.

Fuel Injector Installation Lubricate "O" rings with automatic transmission fluid. Scheme 43

Fuel Injection System Wiring Diagram. Scheme 44

1. Install new fuel pressure regulator dust seal in fuel meter body recess in rear unit. Install new fuel return passage gasket. Install new fuel meter cover gasket on fuel meter body.
2. Install fuel meter cover with pressure regulator on rear unit. Install fuel meter cover with accumulator on front unit. Apply thread locking compound (supplied in service kit) to 5 cover screws. Install lock washers and screws (2 short screws go next to injector). Tighten screws.

Note. Pressure regulator has a taller regulator "can" than the accumulator assembly.

Place throttle valve in normal closed idle position. Install TPS on rear throttle body with pick-up lever above throttle actuator lever tang. Install retainer, lock washers and 2 new attaching screws (coated with locking compound).

Note. TPS adjustment must be done with throttle body installed on vehicle. See appropriate TUNE-UP article.

Exploded View of Rochester Dual Unit (Crossfire) Throttle Body Assembly (Exploded View of Front Unit is Typical for Rear Unit). Scheme 45

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS