GM Cadillac 1967-1989 Repair Guide

Fuel Filter

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CARBURETED ENGINES



The gasoline engine fuel filter should be replaced every year or 15,000 miles or more often if necessary.

On 1967-74 models the fuel filter is mounted inside the fuel pump. From 1975 and later the filter is located in the carburetor behind the fuel inlet nut. Beginning in 1976, a check valve is included in the fuel filter.

1967-74 Vehicles

To replace the inlet (located at the fuel pump) fuel filter:

  1. Jack up the car and support on jackstands.
  2.  
  3. Place some absorbent rags under the fuel fittings to catch any fuel which may spill, when the fitting is removed.
  4.  
  5. Clamp closed the fuel inlet hose on the fuel pump.
  6.  
  7. Disconnect the fuel pump outlet line at the fuel pump.
  8.  
  9. Remove the fuel outlet nut and remove the fuel filter.
  10.  

Use two wrenches to prevent loosening of the nut welded to the pump cover.

  1. To install, reverse the above procedure.
  2.  

1975-89 Vehicles

See Figure 1

To replace the inlet (carburetor body) fuel filter:

  1. Place some absorbent rags under the fuel fittings to catch the gasoline which will spill out when the lines are loosened.
  2.  
  3. Disconnect the fuel line connection at the intake fuel filter nut. Plug the opening to prevent loss of fuel.
  4.  
  5. Remove the intake fuel filter nut from the carburetor with a box wrench or socket.
  6.  
  7. Remove the filter element and spring.
  8.  

To install:
  1. The filter element can be cleaned in solvent and blown dry. However, for the low cost of a new filter it is more advisable to simply install a new element.
  2.  
  3. Install the element spring, then the filter element in the carburetor.
  4.  
  5. Install a new gasket on the intake fuel nut, then install the nut in the carburetor body and tighten securely.
  6.  
  7. Install the fuel line and tighten the connector. Check for leaks at all fittings with the engine idling.
  8.  



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Fig. Fig. 1: Fuel filter - 1978-89 carbureted engines

FUEL INJECTED ENGINES



See Figures 2, 3, 4, 5, 6 and 7

The fuel filter on fuel injected vehicles may be located in one of two locations. On all 1976-79 vehicles except the Seville, the filter is mounted in the engine compartment near the fuel pump. On the 1976-79 Seville, and all 1980-85 vehicles, the fuel filter is located on the left side of the chassis just ahead of the rear axle. On 1986-89 vehicles, the filter can be found near the frame, in back of the left front wheel. There are two types of fuel filters used on the gasoline fuel injected vehicles, the one-piece disposable inline filter, used on all 1982-86 250 and 1988-89 273 V8 engines, and the replaceable element type filter used on all the other engines.


CAUTION
Fuel is under high pressure: if the steps below are not followed, the fuel could spray out and result in a fire hazard and possible injury.

  1. Disconnect the negative battery terminal.
  2.  
  3. Release the pressure from the fuel system:
  4.  
  5. Without pressure fitting: Cars without a pressure fitting in the fuel line, cover the fitting to be removed with a shop towel while loosening so that fuel will be absorbed. Dispose of gasoline properly.
  6.  
  7. With pressure fitting: Locate the pressure fitting in the fuel line and remove the protective cap. Loosely install a special valve depressor (G.M. tool no. J-5420) on the fitting. Wrap a towel around the fitting to block any spray and slowly tighten the tool until the pressure has been relieved.
  8.  

  1. Replace the filter as follows:
    1. On the replaceable element type filter; the fuel filter element is replaced by unscrewing the bottom cover and removing the filter element. Replace the element and gasket with an AC type GF 157 or equivalent. Hand tighten the bottom cover.
    2.  
    3. On the in-line disposable type filter; the fuel filter canister is replaced by loosening the fitting on the end of the filter, then use a pair of pliers to expand the clamp on the other end and slide it down past the point where the hose extends over the inlet of the filter. Gently twist and remove the hose, unscrew and remove the fitting. Remove and discard the old filter. Install the new filter into the hose and replace the clamp. Reinstall the fitting, and check for leaks with the engine idling.
    4.  

  2.  

A dry fuel system on cars equipped with EFI/DFI may require a substantial cranking period before starting. Be sure to crank the engine in short bursts, allowing time for the starter motor to cool between each burst.

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Fig. Fig. 2: Fuel filter location, disposable type - 1986-87 8-250 and 1988-89 8-273 engines



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Fig. Fig. 3: Fuel filter location, sealed type - 8-250 and 8-273 engines



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Fig. Fig. 4: Common fuel filter location - lower right corner



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Fig. Fig. 5: Removing the fuel filter hose clamp



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Fig. Fig. 6: Removing fuel filter lines - always use a back-up wrench



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Fig. Fig. 7: Removing fuel filter mounting

DIESEL ENGINES



See Figures 8 and 9

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 should be changed every 30,000 miles or two years.

To install a new filter:
  1. With the engine cool, place absorbent rags underneath the fuel line fittings at the filter.
  2.  
  3. Disconnect the fuel lines from the filter.
  4.  
  5. Unbolt the filter from its bracket.
  6.  
  7. Install the 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.
  8.  

The GM diesel cars 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 be activated manually, if the engine temperature is above 125°F (52°C). Activating the H.P.C.A. will reduce engine cranking time.To activate the H.P.C.A. 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. When the new filter element is installed, check for leaks.



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Fig. Fig. 8: Diesel fuel filter and lines



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Fig. Fig. 9: H.P.C.A. solenoid activation, diesel engine

 
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