Engine Controls - Removal, Installation & Overhaul - 7.4l (G Series) Chevrolet Chevy Van G3500

INTRODUCTION

This article contains removal, overhaul and installation procedures (when information was available at time of publication). If component removal and installation is primarily an unbolt and bolt-on procedure, only a torque specification may be furnished.

POWERTRAIN CONTROL MODULE (PCM)

Note. Before replacing PCM, carefully inspect all wiring and control components. Failure to test for short circuits may result in repeated PCM failure due to shorts and Quad-Driver failure. To prevent internal damage to PCM, ensure ignition switch is in OFF position when connecting or disconnecting PCM connectors or any electrical components.

Note. When replacing defective PCM, remove knock sensor module from defective PCM. New PCM does not come equipped with knock sensor module. Install knock sensor module into new PCM.

Ensure ignition switch is in OFF position. Disconnect negative battery cable. Unplug electrical connectors from PCM. Remove PCM from vehicle. Remove access cover and remove knock sensor module from PCM.

Install knock sensor module in NEW PCM. Install access cover. Install PCM into vehicle. Connect electrical connectors to PCM. Reconnect negative battery cable.

ELECTRICALLY ERASABLE PROGRAMMABLE READ-ONLY MEMORY (EEPROM)

EEPROM is a permanent memory that is part of PCM. EEPROM cannot be replaced. EEPROM contains program and calibration information that PCM uses to control powertrain. If PCM is replaced, ensure that NEW PCM software/calibration is correct and most recent version for vehicle. EEPROM must be programmed when new PCM is installed. Program EEPROM using latest software for that specific vehicle.

Removal & Installation

1. KS module is located in PCM. Disconnect negative battery cable. Remove PCM from vehicle. See «POWERTRAIN CONTROL MODULE (PCM)»(/chevrolet/chevy-van-g3500/1996-1998/remont/removal-installation/#engine-controls-removal-installation-overhaul-74l-g-series__powertrain-control-module-pcm) . Position PCM with access cover up. Remove access cover from PCM.
2. Using thumb and forefinger, squeeze both ends of knock sensor module inward and pull module up from access hole. To install, reverse removal procedure. Ensure module latches into holder in PCM.

Note. If PCM is replaced, KS module must be transferred from original to replacement PCM.

CAMSHAFT POSITION (CMP) SENSOR

CMP sensor is located inside the ignition distributor. To replace sensor, disconnect negative battery cable. Remove distributor cap. Disconnect sensor harness connector. Remove sensor retaining screw. Remove CMP sensor. (Scheme 29) To install, reverse removal procedure.

Scheme 29

CRANKSHAFT POSITION (CKP) SENSOR

CKP sensor is a magnetic sensor which is located in front of engine, behind crankshaft pulley. (Scheme 30)

Scheme 30

KNOCK SENSOR (KS)

Note. Cooling system may need draining prior to removing knock sensor.

Knock sensor is located on side of engine block. (Scheme 31) Disconnect negative battery cable. Disconnect wiring harness connector from knock sensor. Remove knock sensor. To install, reverse removal procedure. Install sealant to sensor threads prior to installation. Tighten knock sensor to 14 ft. lbs. (19 N.m).

Scheme 31

DISTRIBUTOR

Note. There are 2 procedures available to install the distributor. Use installation procedure No. 1 when the crankshaft has NOT been rotated from the original position. Use installation procedure No. 2 when any of the following components are removed: Intake Manifold Cylinder Head Camshaft Timing Chain or Sprockets Complete Engine

1. Turn OFF the ignition switch.
2. Remove spark plug wires from the distributor cap.
3. Remove electrical connector from the base of the distributor.
4. Remove 2 screws that hold the distributor cap to the housing.
5. Discard screws.
6. Remove distributor cap from housing.
7. Use a grease pencil in order to note the position of the rotor in relation to the distributor housing. The mark is identified in the illustration as the number "1". (Scheme 32)
8. Mark distributor housing and intake manifold with a grease pencil.
9. Remove mounting clamp hold down bolt.
10. Remove distributor. (Scheme 33)
11. As the distributor is being removed from the engine, watch the rotor move in a counterclockwise direction about 42 degrees. This will appear as slightly more than one o'clock position.
12. Note the position of the rotor segment. Place a second mark on the base of the distributor. This will aid in achieving proper rotor alignment during the distributor installation. The second mark on the distributor housing is identified in the graphic as number 2. (Scheme 34)

1. If installing a new distributor assembly, place two marks on the new distributor housing in the same location as the two marks on the original housing.
2. Remove new distributor cap, if necessary.
3. Align rotor with mark made at location 2. (Scheme 34)
4. Guide distributor into engine. Ensure that the mounting hole in the distributor hold-down base is aligned over the mounting hole in the intake manifold.
5. As distributor is being installed, observe the rotor moving in a clockwise direction about 42 degrees.
6. Once the distributor is completely seated, the rotor segment should be aligned with the mark on the distributor base in the location number "1". (Scheme 32) If the rotor segment is not aligned with the number "1" mark, the driven gear teeth and the camshaft have meshed one or more teeth out of alignment. In order to correct this condition, remove the distributor and reinstall it.
7. Install the distributor mounting clamp. Tighten the distributor clamp bolt to 18 ft. lbs. (25 N.m). Install the distributor cap.
8. Install 2 NEW distributor cap screws. Tighten the screws to 21 INCH lbs. (2.4 N.m). (Scheme 35)
9. Install electrical connector to distributor.
10. Install spark plug wires to distributor cap.

Procedure 2

1. Position No. 1 cylinder to Top Dead Center (TDC) of the compression stroke.
2. Align White paint mark on the bottom stem of the distributor, and the pre-drilled indent hole in the bottom of the gear (3 in illustration). (Scheme 36)
3. With the gear in this position, the rotor segment should be positioned as shown (2 in illustration). (Scheme 36) The alignment will not be exact. If the driven gear is installed incorrectly, the dimple will be approximately 180 degrees opposite the rotor segment when it is installed in the distributor. NOTE: The OBD II ignition system distributor driven gear and rotor can be installed in multiple positions. In order to avoid mistakes, make sure to mark the distributor in the following positions: The distributor driven gear. The distributor shaft. The rotor holes for the same mounting position upon reassembly. Installing the driven gear 180 degrees out of alignment, or locating the rotor in the wrong holes, will cause a no-start condition. Premature engine wear or damage may result.
4. Using a long screw driver, align the oil pump drive shaft to the drive tab of the distributor.
5. Guide the distributor into the engine. Ensure the spark plug towers are perpendicular to the centerline of the engine.
6. Once the distributor is properly seated, the rotor segment should be aligned with the pointer cast into the distributor base. The pointer must have an "8" cast onto it (a "6" indicates a V6 engine component). (Scheme 37) If the segment does not come within a few degrees of the pointer, the gear mesh between the distributor and the camshaft may be off a tooth or more. If this is the case, repeat the procedure again in order to achieve proper alignment.
7. Install the distributor mounting clamp. Tighten the distributor clamp bolt to 18 ft. lbs. (25 N.m). Install the distributor cap.
8. Install the NEW distributor cap screws. Tighten the screws to 21 INCH lbs. (2.4 N.m). (Scheme 35)
9. Install the electrical connector to the distributor. Install the spark plug wires to the distributor. CAUTION: If the MIL is turned on after installing the distributor, and a DTC is found, the distributor has been installed incorrectly. Refer to installation Procedure 2 for proper distributor installation.

Scheme 32

Scheme 33

Scheme 34

Scheme 35

Scheme 36

Scheme 37

FUEL SYSTEM PRESSURE RELIEF

1. Disconnect negative battery cable. Loosen fuel filler cap to relieve fuel tank pressure. Install Fuel Pressure Gauge (J-34730-1) to fuel pressure connection.
2. Wrap shop towel around pressure connection when installing fuel pressure gauge to absorb fuel leakage. Place gauge bleed hose into suitable container. Open bleed valve to bleed fuel pressure.

1. Disconnect the negative battery cable.
2. Relieve the fuel system pressure. Refer to «FUEL SYSTEM PRESSURE RELIEF»(/chevrolet/chevy-van-g3500/1996-1998/remont/removal-installation/#engine-controls-removal-installation-overhaul-74l-g-series__fuel-system-pressure-relief) . Have a dry chemical (Class B) fire extinguisher nearby.
3. Turn the filter housing counterclockwise and allow the fuel remaining in the filter housing to drain into an approved container.
4. Remove the fuel filter housing and gasket from the base.
5. Remove the fuel filter cartridge.
6. Inspect the inside of the housing for signs of rust or corrosion. Discard the housing if rust or corrosion is present.

1. Install a new housing gasket. Apply a few drops of clean engine oil to the gasket.
2. Install the new filter cartridge.
3. Connect the housing to the base. Tighten Tighten the filter housing until the gasket seats. Tighten filter housing 3/4 of a turn after gasket contacts.
4. Turn ON the ignition switch for 2 seconds. Turn OFF the ignition switch for 10 seconds. Again, turn the ignition switch to the ON position. Check for fuel leaks.

IN-LINE FUEL FILTER REPLACEMENT (NON-CARTRIDGE TYPE FILTER)

1. Disconnect the negative battery cable.
2. Relieve the fuel system pressure. Refer to «FUEL SYSTEM PRESSURE RELIEF»(/chevrolet/chevy-van-g3500/1996-1998/remont/removal-installation/#engine-controls-removal-installation-overhaul-74l-g-series__fuel-system-pressure-relief) .
3. Disconnect the fuel feed pipes at the filter.
4. Remove the in-line fuel filter clamp attaching hardware.
5. Remove the clamp from the filter.

1. Remove the protective caps from the new filter.
2. Install the clamp to the filter.
3. Install the in-line filter clamp attaching hardware. Install in the same positions as on the old filter noting direction of fuel flow arrow.
4. Connect the fuel feed pipes to the filter and tighten.
5. Connect the negative battery cable.
6. Turn ON the ignition switch for 2 seconds. Turn OFF the ignition switch for 10 seconds. Again, turn the ignition switch to the ON position. Check for fuel leaks.

FUEL PUMP

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

1. Relieve fuel system pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/chevrolet/chevy-van-g3500/1996-1998/remont/removal-installation/#engine-controls-removal-installation-overhaul-74l-g-series__fuel-system-pressure-relief) under FUEL SYSTEM. Disconnect negative battery cable. Raise vehicle and remove fuel tank. Using Sending Unit Remover (J-36608 or J-24187), remove sending unit and pump by turning cam lock counterclockwise.
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.

Disconnect IAC valve harness connector. Remove IAC valve retaining screws and remove IAC valve from upper intake manifold assembly.

1. Inspect "O" ring for damage. Replace if necessary. If reusing IAC valve, DO NOT push or pull on pintle. Threads on worm gear will be damaged.
2. If replacing IAC valve, measure distance between tip of new IAC valve pintle and mounting flange. Distance should not exceed 1 1/8" (28 mm). If distance is more than specified, use finger pressure to slowly retract pintle. Lubricate "O" ring with clean engine oil.
3. Apply thread locking compound (Loctite 262) to IAC valve retaining screw threads. Install IAC valve to throttle body. Tighten IAC valve retaining screws to 27 INCH lbs. (3 N.m). Connect IAC valve harness connector.
4. To reset IAC valve pintle position, turn ignition on for 5 seconds. Turn ignition off for 10 seconds. Start engine and check for proper idle operation. Repeat IAC valve resetting procedure if proper idle operation cannot be obtained.
5. Connect IAC valve harness connector and install air cleaner. Start engine and allow it to reach normal operating temperature. Drive vehicle. It may be necessary to reset idle speed. To reset, disconnect negative battery cable for 10 seconds and reconnect. Cycle ignition on with engine off for 5 seconds. Turn ignition off for 10 seconds and restart vehicle. Proper idle will be initialized.

1. Disconnect negative battery cable. Remove air inlet duct fastener and duct. Disconnect IAC valve and TP sensor electrical connectors. Disconnect throttle and cruise control cables.
2. Remove accelerator cable bracket bolts and bracket. Remove wiring harness fastener nut and throttle body retaining studs. Remove throttle body assembly. Remove flange gasket and discard.
3. Clean gasket surface on intake manifold and throttle body. Install NEW flange gasket. Install throttle body. Install throttle body studs and wiring harness. Tighten throttle body studs to 18 ft. lbs. (24 N.m). To complete installation, reverse removal procedure. Ensure throttle and cruise control linkage does not hold throttle open.

UPPER INTAKE MANIFOLD ASSEMBLY (CSI)

Note. For further information, see UPPER INTAKE MANIFOLD under REMOVAL & INSTALLATION in 7.4L V8 - TRUCKS article.

1. Disconnect negative battery cable. Remove air inlet fastener and duct. Disconnect injector electrical connector. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/chevrolet/chevy-van-g3500/1996-1998/remont/removal-installation/#engine-controls-removal-installation-overhaul-74l-g-series__fuel-system-pressure-relief) under FUEL SYSTEM.
2. Disconnect throttle and cruise control cables from throttle lever cam and bracket. Disconnect power brake and crankcase ventilation valve vacuum hoses at upper manifold and valve cover. Disconnect electrical harness connectors from TP sensor, IAC valve and MAP sensor.
3. Disconnect No. 1 plug wire from distributor cap. Remove fuel pipe clip retaining bolt. Remove injector fuel inlet and outlet pipe retainer and nuts. Remove upper manifold assembly, attaching bolts and rear mounting nuts (position canister purge solenoid bracket to one side).

Disassembly

1. When cleaning or replacing upper manifold assembly, remove throttle cable bracket attaching bolts and bracket, throttle body assembly, MAP sensor, crankcase ventilation valve, purge solenoid and power brake booster vacuum pipe fitting. CAUTION: DO NOT soak upper manifold assembly in an immersion type cleaner or any cleaner containing MEK.
2. Upper manifold assembly contains TP sensor, IAC valve and internal throttle shaft sealed ball bearings. These components MUST NOT be subjected to strong solvent or cleaner bath. Clean throttle bore and valve deposits with carburetor cleaner and a shop towel. Use care when cleaning gasket surfaces. Sharp tools may damage sealing surfaces.

To install, reverse removal procedure. Tighten upper manifold assembly mounting nuts to 10 ft. lbs. (14 N.m) using an alternating, diagonal pattern starting from the center.

1. Remove air cleaner assembly. Disconnect electrical connector from TP sensor. Remove attaching screws, lock washers, retainers, and TP sensor.
2. To install, reverse removal procedure. Adjust TP sensor to specification. See the «ADJUSTMENTS - 7.4L»(/chevrolet/chevy-van-g3500/1996-1998/remont/adjustments/#engine-performance-system-adjustments-74l-g-series) article. When replacing a TP sensor, ensure correct part number is used. Use Loctite on TP sensor attaching screws.

OXYGEN SENSOR

1. Oxygen sensor is mounted in the exhaust pipe, below exhaust manifold. Ensure sensor is free of contaminants. DO NOT use 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. Disconnect electrical connector from oxygen sensor. Carefully remove oxygen sensor from exhaust pipe.

1. Whenever oxygen sensor is removed, coat threads with anti-seize compound before reinstalling. New oxygen sensors 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

TORQUE SPECIFICATIONS

See also:
• 7.4L V8 - TRUCKS
• ADJUSTMENTS - 7.4L
• POWERTRAIN CONTROL MODULE (PCM)
• FUEL SYSTEM PRESSURE RELIEF