Fuel Injection System - 2.5l Tbi Chevrolet Cab & Chassis C20

COMPONENT TESTING

Note. (Scheme 65)and (Scheme 66).

Fuel System Diagnosis. Scheme 65

Injector System Diagnosis. Scheme 66

Removal & Installation

1. Disconnect battery negative cable. Relieve pressure in fuel lines. Lower fuel tank. Remove fuel lever sending unit and pump assembly by turning cam lock ring counterclockwise.
2. Lift assembly from fuel tank and remove fuel pump from fuel lever sending unit. Pull fuel pump up into attaching hose while pulling outward away from bottom support. Make sure not to damage rubber insulator and strainer. To install, reverse removal procedure.

Removal

1. Relieve pressure in fuel lines. Remove air cleaner. Disconnect throttle linkage, return spring and cruise control linkage (if equipped). Disconnect and identify all electrical connectors from throttle body.
2. Disconnect and identify all vacuum hoses from throttle body for installation reference. Disconnect fuel lines from throttle body using 2 wrenches. Remove 3 throttle body-to-manifold bolts. Remove throttle body.

Installation

To install, reverse removal procedure and note the following: Ensure throttle body and intake manifold sealing surfaces are clean. Always use new throttle body-to-manifold gasket.

ADJUSTMENTS

Note. See appropriate article in TUNE-UP section.

DISASSEMBLY

Note. Before performing any service on throttle body assembly, place throttle body on Holding Fixture (J-9789-118 or BT 30-15) to prevent damage to throttle valve.

Fuel Meter Cover

1. Remove 5 cover-to-meter body screws and lock washers. Lift off fuel meter cover with fuel pressure regulator assembly attached. DO NOT remove fuel meter cover gasket. (Scheme 68) WARNING: DO NOT remove screws attaching pressure regulator to fuel meter cover. The pressure regulator includes a spring under heavy tension which may cause personal injury if released. DO NOT immerse cover and regulator assembly in any type of cleaning solvent.
2. Remove fuel pressure regulator dust seal from fuel meter body.

Removing Fuel Meter Cover Assembly Do not remove fuel meter cover gasket at this time. Scheme 67

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. (Scheme 69) NOTE: Use care in removing injector to prevent damage to electrical connectors, fuel filter and nozzle. Injector is serviced as complete assembly only.
2. Remove small "O" ring from the nozzle end of injector. Carefully rotate injector filter back and forth to remove from base of injector. Remove large "O" ring and steel back-up washer at top of injector cavity in fuel meter body.

Fuel Injector Assembly Removal Keep fuel meter cover gasket in place until injector is removed. Scheme 68

Fuel Meter Body

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

Throttle Body

1. Disassembly of throttle body unit for immersion in cleaning solvent requires removal of TPS and IAC assembly. 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 2 TPS attaching screws, lock washers and retainers. Remove TPS from throttle body. (Scheme 70)
3. If necessary, remove TPS actuator lever-to-throttle shaft screw. Remove IAC assembly from throttle body. Remove and discard IAC gasket.

Removing TPS Assembly Invert throttle body unit to remove TPS. Scheme 69

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 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 «COMPONENT TESTING»(/chevrolet/cab-chassis-c20/1985-1986/remont/testing-diagnostics/#fuel-injection-system-25l-tbi__component-testing) .

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 assembly of throttle body is complete.

Note. Before installing IAC assembly, measure distance that valve extends from motor housing. Measuring from gasket mounting surface of housing to end of pintle, 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 insulator gasket on throttle body. Cut-out portions of gasket must match cut-outs 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.

Scheme 70

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. 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 70) 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. (Scheme 70): Fuel Injector Installation Lubricate "O" rings with automatic transmission fluid.
3. 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. 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.

1. Install new fuel pressure regulator dust seal in fuel meter body recess. Install new fuel return passage gasket. Install new fuel meter cover gasket on fuel meter body.
2. Install fuel meter cover. Ensure pressure regulator dust seal and gaskets are properly positioned. Apply thread locking compound (supplied in service kit) to 5 cover screws. Install lock washers and screws (2 short screws go next to injectors). Tighten screws.

Exploded View of Rochester Single Unit Throttle Body Assembly. Scheme 71

Throttle Position Sensor (TPS)

Place throttle valve in normal closed idle position. Install TPS on throttle body with pick-up lever above throttle actuator lever. 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 article in TUNE-UP section.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

Fuel Injection Wiring Diagram. Scheme 72

See also:
• COMPONENT TESTING