Fuel Pressure: Testing and Inspection

1. Fuel system pressure must be released each time a fuel hose is to be disconnected. Perform fuel system pressure release.
2. Remove protective cover from service valve on the fuel rail.
3. Connect fuel pressure gauge C-4799-A to fuel rail service valve.
4. Using diagnostic tester, with the key in the "Run" position, use ASD Fuel System Test, this will activate the fuel pump and pressurize the system. If the gauge reads 330 Kpa +/- 14 Kpa (48 psi +/- 2 psi), pressure is correct and further testing is not required. If pressure is not correct, record the pressure and remove gauge. Use ASD Fuel System Test to reactivate the fuel pump. Insure fuel does not leak from the fuel rail service valve. Reinstall protective cover.

CAUTION: When using the ASD Fuel System Test, the Auto Shutdown (ASD) Relay will remain energized for 7 minutes or until the test is stopped, or until the ignition switch is turned to the "Oft" position.

5. If fuel pressure is below specifications, install tester in the fuel supply line, between the fuel tank and fuel filter at the rear of vehicle.
6. Repeat test. If pressure is at least 5 psi higher than previously recorded pressure, replace fuel filter. If no change is observed, gently squeeze return hose. If pressure increases, replace pressure regulator. If no change is observed, problem is either a plugged pump filter sock or defective fuel pump.
7. If pressure is above specifications, remove the fuel return line hose from the chassis line at fuel tank and connect a 3 foot piece of fuel hose to the return line. Put the other end into an approved gasoline container (minimum 2 gallon size) so that all return fuel will flow into container. Repeat test. If pressure is now correct, check in-tank return hose for kinking. Replace fuel tank assembly if in-tank reservoir check valve or aspirator jet is obstructed. (This test should be performed when fuel tank is 1/2 full or greater.)
8. If pressure is still above specifications, remove fuel return hose from fuel pressure regulator. Connect a substitute hose to the fuel pressure regulator nipple and place other end of hose in clean container. Repeat test. If pressure is now correct, check for restricted fuel return line. If no change is observed, replace fuel pressure regulator.