GM Full-Size Trucks 1980-1987 Repair Guide

Diesel Fuel Filter

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REMOVAL & INSTALLATION



350 Engine

The diesel fuel filter is mounted on the rear of the intake manifold, and is larger than that on a gasoline engine because diesel fuel generally is dirtier (has more suspended particles than gasoline).

The diesel fuel filter should be changed every 30,000 miles or two years.

  1. Make sure the ignition is off.
  2.  
  3. With the engine cool, place absorbent rags underneath the fuel line fittings at the filter.
  4.  
  5. Disconnect the fuel lines from the filter.
  6.  
  7. Unbolt the filter from its bracket.
  8.  
  9. Install a new filter. Start the engine and check for leaks. Run the engine for about two minutes, then shut the engine off for the same amount of time to allow any trapped air in the injection system to bleed off.
  10.  

Some GM diesel trucks equipped with the 350 engine also have a fuel filter inside the fuel tank which is maintenance-free. If the filter element ever becomes clogged, the engine will stop. This stoppage is usually preceded by a hesitation or sluggish running. General Motors recommends that after changing the diesel fuel filter, the Housing Pressure Cold Advance (HPCA) be activated manually, if the engine temperature is about 125ºF. Activating the HPCA will reduce engine cranking time. To activate the HPCA solenoid, disconnect the two-lead connector at the engine temperature switch and bridge the connector with a jumper. After the engine is running, remove the jumper and reconnect the connector to the engine temperature switch. Once the new filter element is installed, start the engine and check for leaks.

379 Engine

See Figures 1, 2 and 3

On 1982-83 models, there is a primary fuel filter attached to the firewall and a secondary fuel filter mounted to the back of the manifold. If it should be necessary to drain water from the fuel tank, also check the primary fuel filter for water and drain as outlined below.

The 1984-87 engines use an in-line type filter which acts as a filter, water separator, water detector, water drain and a fuel heater.



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Fig. Fig. 1: Draining water from the primary fuel filter, 379 diesel



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Fig. Fig. 2: Secondary fuel filter installation, 379 diesel



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Fig. Fig. 3: Fuel filter, 1984-87 379 diesel engine

1982-83 PRIMARY FILTER

If it should be necessary to check for water proceed as follows:

  1. Open the petcock on the top of the primary filter housing.
  2.  
  3. Place a drain pan below the filter and open the petcock on the bottom of the drain assembly. (Attach a length of hose to the petcock and direct the fluid below the frame).
  4.  
  5. After all water is drained from the filter close the petcock tightly.
  6.  
  7. Replace the filter and fill with clean diesel fuel to prevent engine stalling.
  8.  
  9. Close the upper petcock tightly.
  10.  
  11. Start the engine and let it run briefly. The engine may run roughly for a short time until the air is purged from the system.
  12.  

If the engine continues to run roughly, check to make sure both petcocks are closed tightly.

1982-83 SECONDARY FILTER
  1. Remove the fuel filter lines from the adapter.
  2.  
  3. Remove the fuel filter adapter from the intake.
  4.  
  5. Remove the filter.
  6.  

To install:
  1. Replace the filter and refill with clean diesel fuel to prevent engine stalling after start up.
  2.  
  3. Install the fuel filter to the adapter.
  4.  
  5. Install the fuel filter adapter to the intake.
  6.  
  7. Install the fuel filter lines to the adapter.
  8.  

1984-87
  1. Remove the fuel filter cap to release any pressure or vacuum in the fuel tank.
  2.  
  3. Remove both bail wires.
  4.  
  5. Use a suitable container and drain the fuel from the filter by opening the air bleed and water drain valve.
  6.  
  7. Remove the fuel filter element.
  8.  

To install:
  1. Install a new filter element.
  2.  
  3. Install the bail wires.
  4.  
  5. Close the drain valve.
  6.  
  7. Install a 1 /8 inch inside diameter hose to the air bleed port and the other end of the hose into a suitable container.
  8.  
  9. Disconnect the fuel injection pump shut-off solenoid wire.
  10.  
  11. Crank the engine for 10-15 seconds and then wait one minute for the starter motor to cool. Repeat until clear fuel is observed coming from the air bleed.
  12.  
  13. Close the air bleed.
  14.  
  15. Connect the injection pump solenoid wire.
  16.  
  17. Install the filler cap.
  18.  
  19. Start the engine and check the filter for leaks. Allow the engine to idle for five minutes.
  20.  
  21. Check the fuel filter for leaks and repair as required.
  22.