Chart A-7 Fuel System Diagnosis

Fig. 087 - Chart A-7 - Fuel System Diagnosis:

Fig. 088 - WIRING DIAGRAM for Chart A-7 Fuel System Diagnosis. VIN P:

CHART A-7, FUEL INJECTION

1. Pressure but less than 9 PSI falls into two areas:
a. Regulated pressure but less than 9 PSI-Amount of fuel to injector OK but pressure is too low. System will be lean running and may set Code 44. Also, hard starting cold and overall poor performance.
b. Restricted flow causing pressure drop - Normally, a vehicle with a fuel pressure of less than 9 PSI at idle will not be driveable. However, if the pressure drop occurs only while driving, the engine will normally surge then stop as pressure begins to drop rapidly.
2. Restricting the fuel return line allows the fuel pump to develop its maximum pressure (dead head pressure). When battery voltage is applied to the pump test terminal, pressure should be from 13 to 18 PSI.
3. This test determines if the high fuel pressure is due to a restricted fuel return line or a throttle body pressure regulator problem.