Fuel System Pressure Test

Release fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE under REMOVAL & INSTALLATION in this article. Remove cover from service valve on fuel rail (if equipped). Connect Fuel Pressure Gauge (C-3292) and Adapter Hose (C-4799) to service valve. Connect Diagnostic Readout Box II (DRB-II). Turn ignition on.
Use Actuate Outputs Test "Auto Shutdown Relay" on DRB-II to activate fuel pump. Check reading on testers after system is pressurized. Correct pressure reading should be 55 psi (3.9 kg/cm² ) for turbo models and 48 psi (3.3 kg/cm² ) for 3.0L models. If pressure is high, proceed to step 4). If pressure is low, relocate tester to fuel supply line between fuel filter and fuel tank.
Repeat test and check reading on testers after system is pressurized. If pressure rises about 5 psi (.37 kg/cm² ), replace fuel filter. If not, lightly squeeze return hose. If pressure increases, replace pressure regulator. If no change occurs, inspect fuel filter and filter sock for restriction or malfunction.
If pressure was high in step 2) remove fuel return line from fitting at fuel tank. Attach a 36" piece of fuel hose to fuel return line with the opposite end in an approved gasoline container. Repeat test with fuel flowing into container. If pressure is now correct, check in-tank return hose, resevior check valve and aspirator jet for binding or restriction.
If pressure remains high, remove return hose from fuel pressure regulator. Attach a piece of fuel hose to fuel pressure return line with the opposite end in an approved gasoline container. Repeat test and check reading on testers after system is pressurized. If pressure is now correct, check for restricted fuel return line. If pressure remains high, replace fuel pressure regulator.