Chart A-7B Fuel System Pressure Check

Diagnostic Chart - 1 of 3:

Diagnostic Chart - 2 of 3:

Diagnostic Chart - 3 of 3:

Electrical Schematic:

CIRCUIT DESCRIPTION
When the ignition switch is turned to the "ON" position, the Engine Control Module (ECM) will energize the fuel pump relay for 3 seconds, allowing for fuel pump operation. If the engine is being cranked, or is running, the fuel pump will continue to operate, as long as the ECM is receiving ignition reference pulses. If the ignition reference pulses are not detected, the fuel pump will stop after 3 seconds.

The fuel pump will deliver fuel through the fuel filter and fuel rail to the fuel injectors and fuel pressure regulator, where the system pressure is controlled at 250-300 kPa (36-43 psi) with the ignition switch in the "ON" position and 210-260 kPa (30-37 psi) with the engine idling at normal operating temperatures. Excess fuel is then returned to the fuel tank.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
(Part 1 of 3)
1. Checks to see if fuel system pressure is within specifications with engine not running.
2. Checks to see if fuel system pressure is within specifications with engine idling.
3. This checks for a restricted feed pipe, a faulty fuel pump or a faulty fuel pressure regulator.
(Part 2 of 3)
4. Checks fuel feed pipe and hose connections for leaks.
5. Checks for leakage at fuel pump hose to fuel pump pipe connections or for a faulty fuel pump.
6. Checks for leakage at fuel injector, a faulty fuel pump or for a faulty fuel pressure regulator.
(Part 3 of 3)
7. Checks for internal leaks in fuel tank, a clogged fuel filter or a restricted fuel feed pipe or hose or for a faulty fuel pressure regulator.
8. Checks for a faulty fuel pressure regulator.

DIAGNOSTIC AIDS
Improper fuel system pressure can result in one of the following conditions:
- Cranks, but will not run.
- Cuts out, may feel like ignition problem.
- Poor fuel economy, loss of power.
- Hard starts.