Chart A-7B, Fuel System Diagnosis, Fuel Pressure Check

NOTE: Test numbers refer to test numbers on diagnostic chart.

1. Checks fuel pressure.
2. Restricted flow causing pressure drop. Normally a vehicle with a fuel pressure of less than 32 psi at idle will not be driveable. If pressure drop occurs only while driving, engine will normally surge then stop as pressure begins to drop rapidly to zero.
3. Restricting fuel return line allows fuel pump to develop its maximum pressure (dead head pressure). When ignition is on, the pump should be able to develop pressure greater than 56.9 psi (400 kPa).
4. Test determines if high fuel pressure is due to restricted fuel return line or a throttle body pressure regulator problem.

Fig 1: Chart A-7B, Circuit Wiring Diagram & Flow Chart

Courtesy of GENERAL MOTORS CORP.