Fuel Pump - Mechanical


To determine that the fuel pump is in satisfactory operating condition, tests for both fuel pump pressure and fuel pump capacity should be performed.

  • Fuel pump testers vary depending on the tester manufacturer. Always use the tester according to the recommended procedure.
  • Normally, the procedure for checking a mechanical fuel pump begins by connecting the fuel pump tester between the carburetor inlet fuel line and the inlet nut.
  • Since the tester fittings contain heavy rubber washers, the tester fittings only require hand tightening.
  • Compare the recorded fuel pump pressure and the fuel volume against the specifications for the vehicle.
  • If the pressure or volume is less than specified, check the fuel filter for restrictions, and check the fuel lines for restrictions and leaks before replacing the fuel pump.
  • When air leaks into the fuel line between the fuel pump and the fuel tank, the fuel pump discharges some air with the fuel, which reduces pump volume.
  • When the fuel pump is removed, always check the camshaft lobe or eccentric for wear. The photo below shows the common problems found in a mechanical pump.
Common problems associated with a mechanical fuel pump.