GM Celebrity/Century/Ciera/6000 1982-1996 Repair Guide

Mechanical Fuel Pump


Mechanical fuel pumps are used on 6-2.8L engines. The pump has a vapor return line for both emission control purposes and to reduce the likelihood of vapor lock. The fuel pump is located at the left side of the engine.


See Figure 1

  1. Disconnect the negative cable at the battery. Raise and support the car.
  3. Remove the pump shields and the oil filter, if so equipped.
  5. With a shop towel handy, disconnect the inlet hose from the pump. Disconnect the vapor return hose, if equipped, then wrap the towel around the hose to catch any spilt fuel.
  7. Loosen the fuel line at the carburetor, then disconnect the outlet pipe from the pump. Use another towel or the same one if possible for spilt fuel.
  9. Remove the two mounting bolts and remove the pump from the engine.

To install:
  1. Place a new gasket on the pump and install the pump on the engine. Tighten the two mounting bolts alternately and evenly.
  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.

Click image to see an enlarged view

Fig. Fig. 1: Reinstalling the pipe fittings should be done carefully; make sure not to strip the ends or use the wrong size wrench

  1. Install the inlet and vapor hoses. Install the shields (if equipped) and oil filter. Lower the car, connect the negative battery cable, start the engine, and check for leaks.


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. 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.

Pressure Test
  1. Disconnect the fuel line at the carburetor and connect a fuel pump pressure gauge. Hold the gauge up so that it's approximately 16 inches above the pump. Pinch the fuel return line.
  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 measure 5.5-6.5 psi (38-45 kPa) consistently.
  5. If the pressure is incorrect, replace the pump. If it is okay, go on to the volume test.

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