Theory of Operation
This fuel system uses a low pressure Fuel Lift Pump inside the Fuel Tank to supply fuel to the Tandem Pump through the fuel filter. The Tandem Pump performs two functions. First, the Tandem Pump raises the fuel pressure and supplies the Fuel Injectors. Second, the Tandem Pump creates a vacuum supply which is used by the vacuum operated devices. The fuel return goes back through the Tandem Pump to the Fuel Filter where the fuel can take two different paths. A portion of the fuel will be directed back into the fuel supply inside the Fuel Filter. The remaining fuel will flow back to the Fuel Tank through the Fuel Cooler.
| Possible Causes |
|---|
| FUEL SYSTEM LEAK |
| FUEL CONTAMINATION |
| FUEL LINE RESTRICTIONS |
| FUEL INJECTOR |
| FUEL LIFT PUMP |
| FUEL LIFT PUMP WIRING |
| TANDEM PUMP |