Dodge Omni/Horizon/Rampage 1978-1989 Repair Guide

Mechanical Fuel Pump

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REMOVAL & INSTALLATION



A mechanical fuel pump is located on the left side of the engine.

  1. Disconnect the fuel and vapor lines.
  2.  



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Fig. Fig. 1 Disconnect the fuel and vapor lines

  1. Remove the attaching bolts.
  2.  



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Fig. Fig. 2 Remove the attaching bolts for the pump to the block

  1. Remove the insulator block from the old pump. This may be reused if it is good condition.
  2.  



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Fig. Fig. 3 Remove the insulator block from the old pump. This may be reused if it is good condition

  1. Remove any gasket mating material that may have adhered to the block.
  2.  
  3. Installation is the reverse of removal. Always use a new gasket when installing the pump, then make certain the gasket surfaces are clean.
  4.  



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Fig. Fig. 4 Fuel pump port identification

TESTING



The fuel pump can be tested in a variety of ways, depending on the equipment available.



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Fig. Fig. 5 Fuel pump diagnosis chart

Volume
  1. Disconnect the fuel supply line from the carburetor (leave it connected to the fuel pump).
  2.  
  3. Crank the engine. The fuel pump should supply 1 quart of fuel in 1 minute or less. Do not catch the fuel in a styrofoam container.
  4.  
  5. Reconnect the line to the carburetor.
  6.  

Pressure
  1. Insert a tee fitting in the fuel line at the carburetor.
  2.  
  3. Connect a 6 in. (152mm) maximum piece of hose between the tee and a pressure gauge.
  4.  
  5. Vent the pump for a few seconds to relieve air trapped in the fuel chamber. This will allow the pump to operate at full capacity.
  6.  



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Fig. Fig. 6 Gauge installation for pressure testing the fuel pump

  1. Operate the engine at idle. The pressure should be 4-6 psi (27-41 kPa) and remain constant or return slowly to zero when the engine is stopped. An instant drop to zero when the engine is stopped indicates a leaking outlet valve. If the pressure is too high, the main spring is too strong or the air vent is plugged.
  2.  

Vacuum

The vacuum test should be made with the fuel line disconnected. The minimum reading should be at least 10 in. Hg with the fuel line disconnected at the carburetor.

Inlet Valve Test

A vacuum gauge is needed to test the inlet valve.

  1. Disconnect the fuel inlet line at the fuel pump.
  2.  
  3. Connect a vacuum gauge to the inlet fitting of the fuel pump.
  4.  
  5. Crank the engine.
  6.  
  7. There should be a noticeable vacuum present, not alternated by blowback.
  8.  
  9. If blowback is present, the inlet valve is not seating properly and the pump should be replaced.
  10.  
  11. Remove the vacuum gauge, then reconnect the fuel line.
  12.  

 
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