Mazda Trucks 1972-1986 Repair Guide

Electric Fuel Pump

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On all models through 1984, the pump is mounted on the left frame rail adjacent to the fuel tank.

TESTING



To determine that the fuel pump is in good operating condition, test for both volume and pressure should be performed. The tests are performed with the fuel pump installed, and the engine at normal operating temperature and idle speed.

Be sure that the fuel filter has been changed within the specified interval. If in doubt, install a new filter.

Pressure Test See Figure 1

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Fig. Fig. 1: Pressure and volume testing the electric fuel pump

  1. Remove the air cleaner.
  2.  
  3. Disconnect the fuel inlet line at the carburetor.
  4.  
  5. Connect a pressure gauge, a restrictor and a flexible hose between the fuel filter and the carburetor. Position the flexible hose and restrictor so that the fuel can be discharged into a suitable graduated container.
  6.  
  7. Before taking a pressure reading, operate the engine at idle speed and vent the system into the container by momentarily opening the hose restrictor.
  8.  
  9. Close the hose restrictor and allow the pressure to stabilize and note the reading. It should be 2.8-3.6 psi or 3.6-5.0 psi on the Rotary Pick-Up.
  10.  
  11. If the pump pressure is not within specifications, and the fuel filter and fuel lines are not blocked, the pump is malfunctioning and should be replaced.
  12.  
  13. If the pressure is within specifications, perform the volume test.
  14.  

Volume Test

  1. Open the hose restrictor and expel the fuel into the container, while observing the time required to discharge 1 pint. Close the restrictor. Fuel pump volume should be approximately 2 pints/minute or 1.2 quarts/minutes on the Rotary Pick-Up.
  2.  
  3. If the pump volume is below specifications, repeat the test using an auxiliary fuel supply and a new filter. If the pump volume meets specifications while using an auxiliary fuel supply, check for a restriction in the fuel lines.
  4.  

REMOVAL & INSTALLATION



  1. Remove the fuel pump shield from the frame. Disconnect the electrical leads from the pump.
  2.  
  3. Disconnect the inlet and outlet lines from the pump. Plug the lines.
  4.  
  5. Unbolt and remove the pump from its mounting bracket.
  6.  
  7. Position the fuel pump on the mounting bracket and install the bolts. Be sure that both mounting surfaces are clean.
  8.  
  9. Connect the inlet and outlet hoses.
  10.  
  11. Connect the electrical leads to the pump.
  12.  
  13. Install the fuel pump shield.
  14.  

 
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