System Diagnosis - Fuel System Operational Pressure Test

Fuel System Pressure Relief:

FUEL SYSTEM OPERATIONAL PRESSURE TEST

WARNING: Do not allow smoking or the use of open flames in the area where work on the fuel system is taking place. Anytime the fuel system is being worked on, disconnect the negative battery cable, except for those tests where battery voltage is required.

1. Remove air induction tube.

WARNING: Whenever fuel line fittings are loosened or disconnected, wrap a shop cloth around fitting while connecting gauge, to collect fuel place the cloth in an approved container.

2. Connect fuel gage bar kit (Saturn Tool) SA9127E to fuel pressure test port. Use 900 adapter SA9403E.
3. Close fuel pressure gauge shut off valve and start engine. Record maximum pressure.
a. Perform pressure test with engine at idle.
b. Check for vacuum at the fuel pressure regulator. If vacuum is not present, inspect vacuum line for kinks, openings, or debris.

Fuel System Pressure Regulator:

NOTE: The fuel rail pressure regulator can be functionally checked by removing the vacuum line at the regulator with the engine's rpm at idle. Fuel system pressure should vary from 40-70 kPa (6-10 psi). If pressure readings do not change, or fuel is found in the vacuum line, the regulator will require replacement. The vacuum line must be free any liquids or debris and a slight vacuum can be felt at the line's inlet when removed at the pressure regulator.

Fuel System Pressure Specifications:

4. If pressure readings are:
Low:
a. Check for bent or pinched fuel lines.
b. Check fuel pump pressure.
c. Replace fuel pressure regulator.
d. Substitute a good fuel filter.
e. Check fuel pump for flow.

High:
a. Check for restricted fuel return line.
b. Replace pressure regulator.

5. Install bleed hose into an approved container and open valve to bleed system pressure. Once pressure is bled, remove gage bar adapter from fuel pressure test port and recap it.
6. Start engine and check for leaks.

NOTE: If a start/stall condition exists after the vehicle has sat for ten hours or less, and fuel pressure readings are extremely low during previous testing, the engine should be warmed up and left to sit overnight with a fuel pressure gage attached. Fuel pressure after ten hours should be approximately 7 kPa (1 psi). If minimal pressure has been maintained, refer to step 4.