GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual

Fuel Pump

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See Figures 1 and 2

All carbureted engines use a mechanical fuel pump, driven off the camshaft and mounted on the engine block.



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Fig. Fig. 1: Fuel pump mounting and hoses-1.9L and 2.0L engines



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Fig. Fig. 2: Fuel pump mounting-2.8L carbureted engine

TESTING



To determine if the pump is in good condition, tests for both volume and pressure should be performed. The tests are made with the pump installed, and the engine at normal operating temperature and idle speed. Never replace a fuel pump without first performing these simple tests.

Be sure that the fuel filter has been changed at the specified interval. If in doubt, install a new filter first. The filter is an inexpensive maintenance item and should be replaced if old or suspect. Start the tests with a visual inspection. Check lines for damage, kinks or restrictions. Make sure all fittings are properly tightened and that there is no leakage from the system.

Pressure Test
  1. Disconnect the fuel line from the carburetor and connect a fuel pump pressure gauge.
  2.  
  3. Start the engine and check the pressure with the engine at idle. If the pump has a vapor return hose, squeeze it off so that an accurate reading can be obtained. Pressure should not be below specification. Most of the carbureted engines covered by this manual are specified between 3-7 psi. Refer to the Tune-Up Specifications chart in Chapter 2 of this manual.
  4.  
  5. If the pressure is incorrect, replace the pump. It if is OK, perform the volume test.
  6.  

Volume Test
  1. Disconnect the fuel feed line from the carburetor.
  2.  
  3. Place the fuel line into a graduated container.
  4.  
  5. Run the engine at idle until one pint of gasoline has been pumped. One pint should be delivered in 30 seconds or less. There is normally enough fuel in the carburetor float bowl to perform this test, but refill it, if necessary.
  6.  
  7. If the delivery rate is below the minimum, check the lines for restrictions or leaks. If none are found, replace the pump.
  8.  

REMOVAL & INSTALLATION



See Figures 3 through 7

When you are disconnecting or connecting the fuel pump outlet fitting, always use 2 wrenches to avoid damaging the pump.

1.9L and 2.0L Engines

The fuel pump is mounted to the front right side of the engine.

  1. Disconnect the negative battery cable.
  2.  
  3. Matchmark and remove the distributor assembly.
  4.  
  5. Disconnect the fuel hoses from the fuel pump. If necessary, tag them to assure proper installation.
  6.  
  7. Remove the engine lifting hook.
  8.  
  9. Remove the fuel pump-to-engine bolts, then remove the fuel pump and discard the old gasket.
  10.  

To install:

Before installing the fuel pump, it may be helpful to rotate the crankshaft so that the cam lobe is on the down stroke. You may wish to temporarily reinstall the distributor in order to preserve ignition timing. New matchmarks should be made.

  1. Use a new gasket and RTV sealant, then install the pump to the engine.
  2.  
  3. Tighten the fuel pump-to-engine bolts to 15 ft. lbs. (20 Nm).
  4.  
  5. Install the engine lifting hook.
  6.  
  7. Connect the fuel hoses to the pump as noted during removal.
  8.  
  9. Align and install the distributor assembly.
  10.  
  11. Connect the negative battery cable, then check and/or adjust the timing.
  12.  

Some vehicles are equipped with a pushrod to actuate the fuel pump rocker arm. In some cases, this pushrod can be a nuisance during pump installation. If so equipped, a small screwdriver or thin plastic tool may be used to hold the pushrod up and out of the way while the fuel pump is installed. Make sure the pump rocker arm is properly located under or behind the pushrod, as applicable. Another method of retaining the pushrod it to pack it into position using grease, though this will only work on a cold engine



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Fig. Fig. 3: When fuel lines are disconnected, expect some fuel to leak out and keep a rag handy



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Fig. Fig. 4: When removing the fuel pump, first disconnect all of the fuel lines



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Fig. Fig. 5: Loosen and remove the pump retaining bolts



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Fig. Fig. 6: Remove the pump from the engine



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Fig. Fig. 7: If necessary, and applicable, remove the pushrod from the engine and check for damage

2.8L Engine

The fuel pump is located on the front left side of the engine.

  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the fuel hoses the from pump. If necessary, tag the lines to assure proper installation.
  4.  
  5. Remove the fuel pump-to-engine bolts and remove the fuel pump from the engine, then remove and discard the old gasket.
  6.  

To install:

Before installing the fuel pump, it may be helpful to rotate the crankshaft so that the cam lobe is on the down stroke.

  1. Use a new gasket and RTV sealant, then install the pump to the engine.
  2.  
  3. Tighten the fuel pump-to-engine bolts to 15 ft. lbs. (20 Nm).
  4.  
  5. Connect the fuel hoses to the pump, as noted during removal.
  6.  
  7. Connect the negative battery cable, then start the engine and check for proper pump operation.
  8.  

 
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