Volkswagen Air Cooled 1949-1969 Repair Guide

Fuel Pump Troubleshooting

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Problems in the fuel system are generally of two different types: fuel pump troubles and carburetor troubles.

Following are some of the problems and possible causes within the mechanically operated diaphragm fuel pump:

  1. Pump leaking at joining faces and losing fuel.
  2.  
    1. Screws insufficiently tightened.
    2.  
    3. Torn fuel pump diaphragm.
    4.  

  3. Diaphragm leaking at rivets and losing fuel.
  4.  
    1. Diaphragm is damaged and must be replaced.
    2.  

  5. Diaphragm material leaky.
  6.  
    1. Diaphragm material is damaged by solvent substance in fuel, and must be replaced.
    2.  

  7. Excessive pump stroke overstraining diaphragm.
  8.  
    1. Pump not installed correctly; gasket too thin.
    2.  

  9. Pump pressure low
  10.  
    1. Pump incorrectly installed; gasket too thick.
    2.  
    3. Spring pressure low.
    4.  

  11. Pump pressure excessive; float needle valve forced down.
  12.  
    1. Pump installed incorrectly; gasket too thin.
    2.  
    3. Spring pressure excessive.
    4.  

  13. Fuel pump inoperative or insufficient fuel delivery.
  14.  
    1. Valves leaky or sticking; top half of pump must be renewed.
    2.  


 
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