Fuel Pressure Test

NOTE: Fuel system pressure must be released each time a fuel hose is to be disconnected. Perform Fuel Pressure Release procedure.

FUEL PRESSURE TEST
- Remove protective cover from service valve on the fuel rail. Connect Fuel pressrue gauge C-4799-A to fuel rail service valve.
- Using diagnostic tester, with the key in the "RUN" position, depress the ATM button, this will activate the fuel pump and pressurize the system.
- If the gauge reads 343-317 Kpa (46-50 psi), pressure is correct and further testing is not required. Reinstall fuel hose using a new original equipment type clamp, and torque to 1 Nm (10 in lb).
- If pressure is not correct, record the pressure and continue with test procedure.

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 "OFF" position.

- 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.
- Repeat test.
- If pressure is 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.
- If pressure is above specifications, remove the fuel return line hose from the chassis line at the 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 pump assembly if in-tank reservoir check valve or aspirator jet is obstructed.

NOTE: This test should be performed when fuel tank is 1/2 full or greater.

- If pressure is still above specifications, remove fuel return hose from throttle body. Connect a substitute hose to the throttle body return nipple and place other end of hose in a clean container. Repeat test.
- If pressure now correct, check for restricted fuel return line.
- If no change is observed, replace fuel pressure regulator.