System Diagnosis - Fuel System Four Hour Pressure Test
FUEL SYSTEM FOUR HOUR 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.
Fuel System Pressure Relief:
2. Connect fuel gage bar kit to fuel pressure test port. Use 90° adapter (Saturn Tool) SA9403E.
NOTE: Engine must be cold when conducting the four hour test.
3. Close fuel pressure gauge shut-off valve.
NOTE: Battery must be at a minimum of 12 volts when performing a fuel system pressure test.
4. Cycle ignition key On/Off several times (do not start engine) and record maximum pressure. Cycle the key On and Off several times (fuel pump must cycle On/Off a minimum of three times) to establish an accurate reading. Allow gage pressure to stabilize for thirty seconds. Refer to readings in chart:
NOTE: It may be necessary to turn the key On/Off a minimum of three times (the key must be left off 30 seconds) to achieve maximum system pressure.
5. Allow system to bleed off for four hours and check pressure.
NOTE: Battery must be at a minimum of 12 volts.
6. If pressure bleeds off beyond specifications, check for any external leaks.
7. If no external leaks are found, the problem lies in one of three places:
a. Fuel rail pressure regulator
b. Fuel pump
c. Fuel injectors
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 7.
8. Components can be eliminated using the following procedures in this order:
WARNING: Make sure the fuel line connects are fully seated.
a. Perform a four hour pressure regulator/check ball leak down test. Install the fuel rail return plug, (Saturn Tool) SA941OE.
Cycle ignition key On/Off several times (do not start engine) and record maximum pressure. Cycle the key On and Off several times (fuel pump must cycle On/Off a minimum of three times) to establish an accurate reading. Allow gage pressure to stabilize for thirty seconds. Refer to readings in chart:
NOTE: It may be necessary to turn the key On/Off a minimum of three times (the key must be left off 30 seconds) to achieve maximum system pressure.
If pressure remains within specification, replace the fuel rail pressure regulator; if pressure bleeds off beyond specification, go to the next step.
WARNING: Make sure the fuel line connects are fully seated.
b. Perform a four hour fuel pump leak down test. Attach the gage bar kit (Saturn Tool) SA9127E to the inlet line.
Cycle ignition key On/Off several times (do not start engine) and record maximum pressure. Cycle the key On and Off several times (fuel pump must cycle On/Off a minimum of three times) to establish an accurate reading. Allow gage pressure to stabilize for thirty seconds. Refer to readings in chart:
NOTE: It may be necessary to turn the key On/Off a minimum of three times (the key must be left Off 30 seconds) to achieve maximum system pressure.
If pressure bleeds off beyond specification, replace the fuel pump, if pressure remains within specification, go to the next step.
WARNING: Make sure the fuel line connects are fully seated.
c. Perform a fuel injector leak test. Remove the rail and place a clean white towel under injectors. Attach the gage bar kit (Saturn Tool) SA9127E to the fuel pressure test port (fuel rail return plug must be installed in fuel rail). Connect fuel inlet line.
Turn ignition key to the On position and observe fuel injector(s) for leakage.
WARNING: Lubricate steel line male ends with clean engine oil. holding steel line, firmly press on female coupler until a click is heard, then pull back to insure a positive engagement. make sure the fuel line connects are fully seated. pinched, kinked or damaged fuel lines must be replaced.
9. Install bleed hose into an approved container and open valve to bleed pressure. Once pressure is bled, remove gauge bar kit from fuel pressure (inlet) line and connect the line. If gage bar adapter is connected to the fuel pressure test port, remove from the test port and recap it.
10. Start engine and check for leaks.