Chart A7 - Fuel System Diagnosis
NOTE:
The following step numbers refer to the step numbers in the accompanying Flow Chart.
- Pressure below 9 psi falls into 2 categories:
- If regulated pressure is less than 9 psi and volume to injector is adequate, system will run lean and cause Code 44. Engine will be hard to start when cold and have poor overall performance.
- A restricted fuel flow is causing pressure drop. Normally, a vehicle with fuel pressure of less than 9 psi at idle will not be driveable. However, if pressure drop occurs only when driving, the engine will surge then stop as pressure begins to drop.
- Restricting the fuel return line allows the fuel pump to develop its maximum pressure. When battery voltage is applied to pump test terminal, pressure should be between 13 to 18 psi.
- This test determines if high fuel pressure is due to a restricted fuel return line or a throttle body pressure regulator problem.