Engine Controls - Remove/install/overhaul Chevrolet Chevy Van G20

INTRODUCTION

Removal, overhaul and installation procedures (when given by manufacturer) are covered in this article. If component removal and installation is primarily an unbolt and bolt on procedure, a simple tightening specification may only be supplied.

ON-VEHICLE ADJUSTMENTS

Note. For adjustments, see ADJUSTMENTS article.

ECM SERVICE CAUTIONS & NOTES

Replacing ECM While Using 3M Anti-Static Mat. Scheme 1

Note. Before replacing ECM, carefully inspect all wiring and control components. Ignition switch must be in OFF position when connecting or disconnecting ECM connector.

Removal

1. Disconnect negative battery cable. Unplug connectors from ECM (behind glove box). (Scheme 1) Remove ECM from vehicle. To remove PROM, position ECM so bottom cover is facing upward. Remove PROM access cover.
2. Note reference notch location in PROM and ECM for reassembly reference. Engage end of PROM carrier with hook end of rocker-type PROM remover. Press on vertical bar end of remover and rock engaged end of PROM carrier up as far as possible.
3. Engage opposite end of PROM carrier in same manner and rock this end up as far as possible. Repeat process until PROM carrier and PROM are free of PROM socket. PROM carrier and PROM should lift off of PROM socket easily.

Note. PROM carrier should ONLY be removed with PROM remover. Use of any other method may damage PROM or PROM socket.

Installation

Install PROM and CALPAC (if equipped) or MEM-CAL in new ECM. Reinstall ECM into vehicle. Reconnect electrical connectors to ECM. Install access panels. Reconnect negative battery cable to battery.

Removal & Installation

Some ECM models use a CALPAC as well as a PROM. (Scheme 2) The CALPAC must also be removed from replaced ECM and installed in new one. Removal and replacement procedures for CALPAC are same as for PROM. See PROGRAMMABLE READ-ONLY MEMORY (PROM) in this article. If units are installed improperly, grounding diagnostic test lead will set Code 52.

Scheme 2

Disconnect negative battery cable. Remove ECM from vehicle. Using 2 fingers, push retaining clips back from MEM-CAL. At same time, grasp it at both ends and lift up out of socket. DO NOT remove MEM-CAL cover.

1. Carefully align MEM-CAL pins with ECM pin holes. DO NOT press in middle of MEM-CAL. Push downward evenly on ends of MEM-CAL until retaining clips on ends of MEM-CAL snap into place.
2. Install ECM. Reconnect negative battery cable. Turn ignition on and ground ALDL connector. Code 12 should flash at least 4 times (if not other codes are present). If Code(s) 42, 43, 51 or 52 are present, or if CHECK ENGINE light stays on constantly with code(s) present, MEM-CAL is not fully seated or defective. If it is necessary to remove MEM-CAL, follow previous removal instructions.

1. Remove ECM from vehicle as previously described. Position ECM so that bottom cover is facing upward. Remove slide-off PROM access cover by depressing locking tab.
2. Using PROM removal tool, grasp PROM at narrow ends. Gently rock PROM from end to end while pulling up. If new PROM is to be installed, remove old PROM from PROM carrier.

Note. Note reference notch locations in PROM, carrier and ECM for reassembly reference.

1. Ensure new PROM has same service number as old one. Place new PROM in PROM carrier. Position squarely over ECM PROM socket. Press on PROM carrier until PROM is firmly seated in ECM. NOTE: Ensure reference notches in both ECM and PROM are properly aligned. If PROM is installed backwards and key is turned on, PROM will be destroyed.
2. Reinstall PROM access cover on ECM. Reinstall ECM in vehicle as previously described. Start engine and ground ALDL diagnostic test connector. Watch for trouble Code 51 or 52.
3. If this occurs, PROM is not fully seated in ECM, installed backwards, has bent pins or is defective. If pins are bent and crack when straightened, PROM must be replaced. If PROM is installed backwards or is defective, it must be replaced.

ELECTRONIC SPARK CONTROL (ESC) MODULE

Note. The ESC is located on a bracket behind the distributor, mounted to firewall.

Turn ignition off. Remove screws holding bracket to firewall. Rotate bracket to access ESC module. Disconnect ESC module harness connector. Remove ESC mounting screws and remove ESC. To install, reverse removal procedure.

Model 700 TBI Unit

Place transmission gear selector in Park (Neutral on manual transmissions). Set parking brake and block drive wheels. Loosen fuel filler cap to relieve tank pressure. Disconnect 3-terminal electrical connector at fuel tank. Start engine and allow to run until engine stalls. Crank engine for 3 seconds to relieve any residual pressure left in fuel lines. Fuel lines are now safe for servicing.

Model 220 TBI Unit

Identifications

An 8-digit unit identification number is stamped on throttle body assembly. On Model 220, number is stamped vertically on front of throttle body at Throttle Position Sensor (TPS) side. On Model 700, number can be found on TPS side of mounting flange. Letter codes are stamped on throttle body at external tube locations to identify vacuum hose connections.

1. Disconnect air cleaner (THERMAC) hose from engine fitting (if equipped). Remove air cleaner, adapter, and gasket. Disconnect electrical leads at IAC valve, throttle position sensor, and fuel injector(s).
2. Relieve fuel pressure as previously described. Disconnect fuel lines from throttle body. Discard fuel line "O" rings. Disconnect grommet with wires from throttle body. NOTE: On model 220 TBI units, squeeze plastic tabs on injectors and pull connector straight up.
3. Disconnect throttle linkage, return spring and cruise control linkage (if equipped). Label and disconnect all vacuum hoses from throttle body. Remove throttle body mount bolts/nut. Remove throttle body.

To install, reverse removal procedure. Ensure throttle body and intake manifold sealing surfaces are clean. Always use new throttle body gasket and fuel line "O" rings. Check fuel system for leaks by turning ignition on, but without starting engine.

Disassembly

Disassembly of throttle body unit for immersion in cleaning solvent requires removal of throttle body cover or fuel meter assembly, TPS and IAC assembly. Throttle valve screws are staked in position and should not be removed. Before working on throttle body assembly, it is essential that residual pressure be relieved before throttle body is removed. See FUEL PRESSURE RELIEF (GASOLINE) in this article.

Throttle Body Cover (Model 220)

Place throttle body on Holding Fixture (J-9789-118 or BT 30-15) to prevent damage to throttle valve. Remove screws holding cover to throttle body, noting location of 2 short screws. Remove throttle body cover. (Scheme 3) Throttle body cover and pressure regulator are serviced as an assembly. DO NOT remove screws attaching pressure regulator to cover.

Fuel Meter Assembly (Model 700)

Remove fuel meter-to-throttle body retaining screws. Remove fuel meter assembly. (Scheme 3) Discard gasket. If fuel pressure regulator cover is removed, regulator diaphragm must be replaced to prevent fuel leaks.

Scheme 3

Cleaning & Inspection

1. Remove TPS, IAC, throttle body cover, fuel meter assembly and pressure regulator assembly, fuel injector, fuel filter, rubber parts and diaphragms. Clean all remaining (metal) parts in a cold immersion-type cleaner such as Carbon X (X-55). Blow dry with compressed air.
2. Inspect mating surfaces for damage that may prevent gasket sealing. Repair or replace faulty components.

Reassembly Throttle Body Cover (Model 220)

1. Install new dust seal into recess of throttle body. Install fuel outlet passage gasket on cover. Install throttle body cover gasket on throttle body. Install cover, making sure that pressure regulator dust seal and cover gaskets are in place.
2. Apply thread locking compound to cover attaching screws. Install cover screws and lock washers. Tighten screws. Connect electrical lead to fuel injector and install air cleaner.

Reassembly Fuel Meter Assembly (Model 700)

1. Install new fuel meter-to-throttle body assembly gasket. Match cutout portions of gasket with openings in throttle body assembly.
2. Place fuel meter assembly on throttle body. Install fuel meter-to-throttle body retaining screws and washers (screws should be coated with locking compound). Tighten screws to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/chevy-van-g20/1985-1995/remont/removal-installation/#engine-controls-removeinstalloverhaul) at end of article.
3. Install new "O" rings on fuel lines. Using a back-up wrench on fuel fittings, tighten fuel line nuts to 20 ft. lbs. (27 N.m). To complete reassembly, reverse disassembly procedure.

Removal (Model 220)

1. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF (GASOLINE)»(/chevrolet/chevy-van-g20/1985-1995/remont/removal-installation/#engine-controls-removeinstalloverhaul) in this article. Remove throttle body cover and leave cover gasket in place. Using screwdriver and fulcrum, carefully pry injector out. (Scheme 4) Remove small "O" ring from nozzle end of injector.
2. Carefully rotate injector fuel filter back and forth to remove fuel filter from base of injector. Remove and discard throttle body cover gasket. Remove large "O" ring and steel back-up washer from top counterbore of throttle body injector cavity.

Installation (Model 220)

1. Install fuel filter on nozzle end of fuel injector. Large end of filter must face injector so that filter covers raised rib at base of injector. Lubricate small "O" ring with ATF and push "O" ring on nozzle end of injector until it presses against injector filter.
2. Install steel back-up washer in top counterbore of throttle body injector cavity. Lubricate large "O" ring with ATF and install "O" ring directly over back-up washer. (Scheme 4) Ensure that "O" ring is seated properly in cavity and is flush with top of throttle body casting. CAUTION: Back-up washer and large "O" ring must be installed before injector. Improper seating of "O" ring will cause fuel leak.
3. Install "O" ring on injector. Install injector into cavity by aligning raised lug on injector base with cast-in notch of throttle body cavity. Push down on injector until fully seated. Electrical terminals of injector will be approximately parallel with throttle shaft. Install throttle body cover.

Removal (Model 700)

Relieve fuel pressure. See FUEL PRESSURE RELIEF (GASOLINE) in this article. Remove fuel injector retainer screw and retainer. Using screwdriver and fulcrum on side of injector opposite connector terminals, carefully pry injector out. (Scheme 4) Remove upper and lower "O" rings and discard.

Scheme 4

Installation (Model 700)

1. Lubricate new upper and lower "O" rings with engine oil and place them on injector. Ensure upper ring is in groove and lower ring is flush against filter.
2. Position injector in fuel meter assembly with electrical connector facing cutout for wire grommet.
3. Push injector down to seat in cavity. Install injector retainer. Coat injector retainer screw with thread locking compound and install. Tighten screw to 27 INCH lbs. (3.0 N.m).

Remove air cleaner and related ducting. Remove Idle Air Control (IAC) electrical connector. On model 220, unscrew IAC valve. On model 700, remove IAC retaining screws and remove IAC valve. Replace as necessary.

1. Inspect gasket or "O" ring for damage. Replace as necessary. Measure distance from IAC contact flange to tip of pintle. Distance should not exceed 1 1/8" (28 mm). If valve is extended too far, damage to valve will result during installation.
2. To set IAC pintle length on a new IAC, use finger pressure to slowly retract pintle. Lubricate new "O" ring with ATF and install new gasket. Install IAC valve on throttle body. Tighten IAC valve to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/chevy-van-g20/1985-1995/remont/removal-installation/#engine-controls-removeinstalloverhaul) at end of article. CAUTION: DO NOT extend or retract pintle if IAC valve has been in service or damage to worm gear will result.
3. Connect electrical lead to IAC valve and install air cleaner. Start engine and allow it to reach normal operating temperature. Drive vehicle at least 43 MPH to allow ECM to reset idle speed. It may be necessary to cycle ignition off and restart vehicle before proper idle will be initialized.

1. Relieve fuel system pressure. See FUEL PRESSURE RELIEF (GASOLINE) in this article. Disconnect negative battery cable at battery. Raise vehicle and remove fuel tank. Remove sender unit and pump by turning cam lock counterclockwise using Tool (J-36608 or J-24187).
2. Remove fuel pump from sending unit by pulling pump up into attaching hose while pulling outward from the bottom support. DO NOT damage rubber insulator or strainer. To install, reverse removal procedure.

Note. When installing sending unit, DO NOT fold or twist strainer. This will restrict fuel flow.

1. Disconnect negative battery cables. On "G" Series, remove engine cover. On all models, disconnect air cleaner at valve cover. Remove crankcase vent bracket.
2. Loosen vacuum pump hold-down clamp. Rotate pump to gain access to intake manifold bolts. Remove injection line clips and intake manifold. Install Protective Covers (J-29664-1) in intake ports.
3. Remove injection line clips. On vans, raise vehicle (for left bank). On all models, disconnect and cap injection lines at injector nozzles. Remove lines at pump. Tag lines for reassembly reference. Cap all openings.

Remove caps and install injection lines. Ensure lines are properly positioned. (Scheme 5) Reverse removal procedure to complete installation. Start engine and check for leaks.

Scheme 5

1. On "R" and "V" models, fuel conditioner filter is located on engine side of cowl. On "C", "K", "G" and "P" models, filter is mounted on rear of intake manifold, under air cleaner. It is accessible by removing engine cover.
2. Remove fuel tank cap to release pressure or vacuum in tank. Place drain pan under drain hose to collect fuel. Drain fuel from filter by opening both air bleed and water drain valves. Using a screwdriver, release fuel conditioner bail wires. Remove filter. (Scheme 6)

Scheme 6

1. Clean filter mount pad. Install new filter element and snap on bail wires. Close water drain valve. Attach a 1/8" inside diameter hose to air bleed and place other end in drain pan.
2. Disconnect fuel injection pump shutoff solenoid wire. Crank engine for 10-15 seconds. Allow starter to cool for one minute. Repeat procedure until clear fuel comes out of air bleed hose.
3. Close air bleed. Connect injection pump shutoff solenoid wire and install fuel tank cap. Start engine and allow to idle for 5 minutes. Check fuel conditioner filter for leaks.

1. Disconnect negative battery cable. Disconnect electrical wiring from fuel pump and fuel pump support bracket.
2. Disconnect fuel lines from fuel pump. Remove support bracket screws and remove support bracket from brake lines. Remove fuel pump and bracket from frame rail.
3. To install, reverse removal procedure. Check for fuel leak at fuel line fittings.

Removal (Pickup)

1. Disconnect negative battery cables. Remove intake manifold. Install Protective Covers (J-29664-1) in intake ports. Remove fuel injection lines. Disconnect throttle cable and detent cable (if equipped). Disconnect wiring, fuel return line, fuel supply line, and fuel injection lines at pump. Cap all openings.
2. Remove A/C hose retainer bracket (if equipped). Remove oil filler tube and vent hose assembly. Remove grommet. Scribe or paint an alignment mark on front cover and injection pump flange.
3. Rotate engine to remove injection pump-to-drive gear retaining bolts accessible through oil filler neck hole. Remove injection pump mount nuts. Remove injection pump and gasket.

1. Install new injection pump gasket. Align locating pin on injection pump hub with slot in injection pump driven gear. At the same time, align injection pump timing marks. Cylinder No. 1 must be set at TDC. (Scheme 7)
2. Attach injection pump to front cover. Alignment marks made during removal must be aligned. Tighten nuts. Attach pump to drive gear and tighten bolts. Reverse removal procedure to complete installation. Check injection pump timing. See INJECTION PUMP TIMING in ADJUSTMENTS article.

Removal ("G" Series)

1. Disconnect negative battery cables. Remove engine cover and intake manifold. Rotate snorkel up and remove air cleaner inlet hose. Remove hood latch. Disconnect cable and move aside.
2. Remove windshield washer bottle, fan shroud bolts and upper fan shroud. Disconnect rubber hose from oil fill tube. Disconnect oil fill tube attaching nuts and remove oil fill tube. Remove oil fill tube grommet.
3. Rotate engine as necessary and remove pump drive gear bolts. Remove fuel filter and bracket including line to injection pump. Disconnect wire looms from injection lines and injection lines at brackets.
4. Disconnect oil pan dipstick tube from left cylinder head. Disconnect electrical connections at injection pump. Disconnect detent cable (if equipped). Disconnect accelerator cable.
5. Remove injection lines. Tag lines for reassembly reference. Cap all openings. Disconnect fuel return line. Scribe or paint a mark on front cover and pump flange. Remove injection pump mount nuts. Remove injection pump. Cap all openings.

Installation ("G" Series)

1. Install new injection pump gasket. Align locating pin on injection pump hub with slot in injection pump driven gear while aligning injection pump timing marks. (Scheme 7)
2. Attach injection pump to front cover. Alignment marks made during removal must be aligned. Tighten nuts. Attach pump to drive gear and tighten bolts. Reverse removal procedure to complete installation. Check injection pump timing. See INJECTION PUMP TIMING in ADJUSTMENTS article.

Scheme 7

Disconnect negative battery cables. Disconnect fuel line clip. Remove fuel return line. Remove fuel injection line. Cap all openings. Using Injector Socket (J-29873), remove injector nozzles(s). Place socket on 1 3/16" (30 mm) hex flats of injector body to prevent damaging injector nozzle.

Remove caps from injector nozzles and fuel lines. Install injector nozzles(s). Install fuel line. Install fuel return line and fuel line clip. Connect battery cables. Start engine and check for leaks.

Purging Fuel System (Diesel)

1. Park vehicle on a level surface. Place drain pan under drain hose to collect fuel. Open drain valve 3-4 turns. With fuel tank cap installed and using air nozzle, apply 3-5 psi (.21-.35 kg/cm 2 ) through fuel return hose at injection pump.
2. Contaminated fuel will be forced out of tank via filter drain hose. Continue to drain fuel until clear fuel is observed. Entire fuel tank may have to be drained. Close drain valve. Install fuel return hose.

Note. If vehicle is equipped with dual tanks, perform purging procedure on each tank.

WATER-IN-FUEL

1. Fuel filter should be drained every 5000 miles or when "WATER-IN-FUEL" warning light glows. Diesel fuel can damage asphalt and painted surfaces. Always place a drain pan under drain hose to collect fuel.
2. Stop vehicle and turn engine off. Apply parking brake. Remove fuel tank cap. Open water drain valve 2-3 turns. Start and allow engine to idle for 2 minutes or until clear fuel is observed. Turn engine off and close water drain valve.
3. Install fuel tank cap. If "WATER-IN-FUEL" warning light comes on after driving a short distance or if engine runs rough or stalls, a large amount of water may be present in fuel tank. Purge fuel system. See PURGING FUEL SYSTEM in ADJUSTMENTS in this article.

Information not supplied by manufacturer.

Disassembly & Reassembly

1. Disassembly procedure not supplied by manufacturer. (Scheme 8)-10 for exploded views.
2. When reassembling, ensure pick-up assembly arm is correctly installed on pin. If not, arm can float and cause ignition timing to vary. To prevent corrosion, ensure terminals are lubricated with petroleum jelly before installation.
3. To prevent heat damage, coat bottom of module and module rest pad in housing with silicone grease. Before installing roll pin in driven gear, ensure timing mark on roll pin and rotor tip align. (Scheme 8)-10.

Scheme 8

Scheme 9

Scheme 10

1. Remove air cleaner assembly. Disconnect electrical lead from TPS sensor. Remove attaching screws, lock washers, retainers, and TPS sensor. To install, reverse removal procedure. Adjust TPS to specification. See ADJUSTMENTS in this article. Use Loctite on TPS attaching screws.
2. On model 220 TBI units, all 2.8L and 7.4L engines use a horizontal electrical connector on the TPS. All other engines with model 220 TBI units, use a vertical electrical connector on the TPS. The sensor mounting configurations are the same. When replacing a TPS ensure correct part number is used.

1. Remove air cleaner assembly and related hoses. Disconnect TPS connector. Remove 2 screws and throttle position sensor from injection pump. (Scheme 11)
2. To install, reverse removal procedure. Lightly tighten screws and adjust TPS. See ADJUSTMENTS article.

Scheme 11

OXYGEN (O2) SENSOR

O2 sensor is mounted in the exhaust pipe just below the exhaust manifold. It is equipped with a permanent pigtail which must be protected from damage when the sensor is removed.

1. Ensure sensor is free of contaminants, avoid using cleaning solvents of any type. Sensor may be difficult to remove when engine temperature is less than 120°F (48°C). Excessive removal force may damage threads in exhaust manifold or pipe.
2. Disconnect negative battery cable at battery. Disconnect electrical connector from oxygen sensor. Carefully remove oxygen sensor from exhaust pipe.

1. Whenever an O2 sensor is removed, threads must be coated with anti-seize compound before it is reinstalled. New O2 sensors will already have this compound applied to threads.
2. Install oxygen sensor in exhaust pipe and tighten sensor to 30 ft. lbs. (41 N.m). Reconnect electrical connector to oxygen sensor. Reconnect negative battery cable.

TORQUE SPECIFICATIONS - GASOLINE

TORQUE SPECIFICATIONS - GASOLINE

TORQUE SPECIFICATIONS - DIESEL

TORQUE SPECIFICATIONS - DIESEL

See also:
• PROGRAMMABLE READ-ONLY MEMORY (PROM)