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1993 Ford Escort FUEL PUMP CIRCUIT (RELAY & INERTIA SWITCH)

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Download 1993 Ford Escort G – TESTS W/CODES – EEC-IV (1.9L)’ ’1993 ENGINE PERFORMANCE Ford Motor Co. – Self-Diagnostics – EEC-IV. CIRCUIT TEST J – FUEL PUMP CIRCUIT (RELAY & INERTIA SWITCH) Diagnostic Aids When ignition switch is in the ON or START position, the PCM connects FUEL PUMP circuit (PCM terminal No. 22) to ground. The fuel pump relay is energized and electrical current flows to the fuel pump. If PCM does not receive ignition PIP signal within 2 seconds, FUEL PUMP circuit is opened and fuel pump operation is terminated. Perform this test when instructed by QUICK TEST or CIRCUIT TEST AA. This test is only intended to diagnose: * Fuel pump relay. * Inertia Fuel Shutoff (IFS) switch. * Wiring harness circuits (B+, VPWR, FUEL PUMP, GND and POWER-TO-PUMP). * Faulty Powertrain Control Module (PCM). Fig. 31: Fuel Pump Monitor Circuit Diagram (Escort & Tracer) 1)Code 87/556: Check VPWR To Fuel Pump Relay Code 87/556 indicates a fuel pump primary circuit failure. Possible causes for this fault are: * IFS switch not reset or circuit open. * Open or shorted circuit. * Faulty fuel pump relay. * Faulty PCM. Disconnect fuel pump relay. Turn ignition on. Measure voltage between chassis ground and VPWR circuit at fuel pump relay wiring harness connector. If reading is 10.5 volts or more, go to step 2). If reading is less than 10.5 volts, verify IFS switch is in ON position. If switch is okay, repair open in VPWR circuit between EEC power relay and fuel pump relay. Connect fuel pump relay and repeat QUICK TEST. 2)Check Fuel Pump Relay Turn ignition off. Disconnect fuel pump relay. Set DVOM on 200-ohm scale. On ISO relays, measure resistance between terminals No. 85 and 86. On all other relays, measure resistance between VPWR pin and FUEL PUMP circuit pin at fuel pump relay. Both resistances should be 40-85 ohms. Set DVOM to 10-k/ohm scale. On ISO relays, measure resistance between terminal No. 85 and terminals No. 30 and 87. On all other relays, measure resistance between FUEL PUMP circuit pin and both POWER-TO- PUMP and B+ pins at fuel pump relay. All resistances should be greater than 10,000 ohms. If resistances are as specified, go to step 3). If resistances are not as specified, replace fuel pump relay and repeat QUICK TEST.

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