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Automotive Technician

A motorist comes into your shop and says that his vehicle is losing power even though the engine is surging.

You check it out yourself and find there is no way to use the pedal to control the amount of thrust you get from the engine. You figure there's a problem with the fuel pump.

This car isn't a model you're familiar with, so you pull out one of your handy manufacturer's repair manuals. You open it to the right section, the one on the fuel system.

You read through the section. Write down a list of the tools needed and a brief summary of the repair procedure.


Mechanical Fuel Pump

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

Testing the Fuel Pump

To determine if the fuel 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 and then test the system.

  1. Disconnect the fuel line at the carburetor and connect a fuel pump pressure gauge. Fill the carburetor float bowl with gasoline.
  2. 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.
  3. If the pressure is incorrect, replace the pump. If it's OK, go on to the volume test.

Volume Test

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


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. Disconnect the inlet hose from the pump. Disconnect the vapor return hose, if equipped.
  3. Loosen the fuel line at the carburetor, then disconnect the outlet pipe from the pump.
  4. 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.
  2. 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.
  3. Install the inlet and vapor hoses. Lower the car, connect the negative battery cable, start the engine, and check for fuel leaks.

How would an auto tech handle this problem?