GM Cavalier/Sunbird/Skyhawk/Firenza 1982-1994

Mechanical Fuel Pump

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A mechanical fuel pump is used on the 1982-84 carbureted engines. It is of the diaphragm-type and because of the design is serviced by replacement only. No adjustments or repairs are possible. The pump is operated by an eccentric on the camshaft.

REMOVAL & INSTALLATION



See Figure 1

The fuel pump is located at the center rear of the engine.

  1. Disconnect the negative cable at the battery. Raise and support the car.
  2.  
  3. Disconnect the inlet hose from the pump. Disconnect the vapor return hose, if equipped.
  4.  
  5. Loosen the fuel line at the carburetor, then disconnect the outlet pipe from the pump.
  6.  
  7. Unfasten the two mounting bolts and remove the pump from the engine.
  8.  



Click image to see an enlarged view

Fig. Fig. 1: Removal and installation of the fuel pump on a carbureted engine

To install:
  1. Place a new gasket on the pump, then position the pump on the engine. Tighten the two mounting bolts alternately and evenly. Refer to the illustration for tightening specifications.
  2.  
  3. Install the pump outlet pipe. This is easier if the pipe is disconnected from the carburetor. Tighten the fitting while backing up the pump nut with another wrench. Install the pipe at the carburetor.
  4.  
  5. Install the inlet and vapor hoses. Lower the car, connect the negative battery cable, start the engine, and check for fuel leaks.
  6.  

TESTING



To determine if the fuel pump is in good condition, tests for both pressure and volume 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 then test the system.

Pressure Test
  1. Disconnect the fuel line at the carburetor and connect a fuel pump pressure gauge. Fill the carburetor float bowl with gasoline.
  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 4.5 psi (31 kPa).
  4.  
  5. If the pressure is incorrect, replace the pump. If it is ok, go on to the volume test.
  6.  

Volume Test
  1. Disconnect the pressure gauge. Run the fuel line into a graduated container.
  2.  
  3. 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.
  4.  
  5. If the delivery rate is below the minimum, check the lines for restrictions or leaks, then replace the pump.
  6.  

 
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