Fuel System Pressure Test
- Release fuel system pressure. Disconnect 5/16" hose from engine fuel line assembly. Connect Fuel System Pressure Testers (C-3292 and C-4749) between fuel filter outlet hose and throttle body. Turn ignition on. Depress Actuation Test Mode (ATM) button on Diagnostic Readout Box (C-4805) to activate fuel pump.
- Check reading on testers after system is pressurized. The correct pressure reading should be 13.5-15.5 psi (.95-1.09 kg/cm2 ). If system pressure is correct, remove testers. Reconnect fuel hose to throttle body using a new hose clamp of same type as original equipment.
- If pressure reading is low, move pressure tester so reading is taken between fuel supply line and fuel filter inlet hose. Repeat pressure test. If reading is correct, replace fuel filter.
- If reading is still low, lightly squeeze fuel return hose. Replace fuel pressure regulator if pressure now increases. If pressure continues to read low, fuel pump is defective or fuel pump intake filter is plugged.
- If pressure reading is high, disconnect fuel return hose at throttle body. Connect separate hose to throttle body/fuel pressure regulator with open end in clean container. Repeat pressure test. If reading is still high, check for plugged fuel injector. If injector is okay, replace fuel pressure regulator. If reading is correct, check all return lines for restrictions.