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HOMESERVICE MANUALSMERCURY1991TRACER BASE, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 5 (ENGINE CONTROLS - SYSTEM/COMPONENT TESTS - EEC-IV)FUEL SYSTEMFUEL DELIVERYFUEL PUMP TESTING
1991 Mercury Tracer Base, 4D Sedan, Automatic

Fuel Pump Testing

1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Fuel Pump Testing
WARNING: This page does not describe the selected car, but rather 15 other vehicles, including the 1993 Mercury Tracer, 1993 Mercury Topaz, 1993 Mercury Sable, 1993 Mercury Grand Marquis, and 1993 Mercury Cougar. However, it is still accessible from the selected car via links, so may be relevant.
  1. Visually inspect fuel delivery system for leaks and damaged lines. Ensure battery is fully charged and fuses are okay. Check fuel tank contents and fuel gauge accuracy.
  2. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE. Install fuel pressure gauge. Turn ignition on to activate pump. Check and record fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. Proceed to appropriate step as indicated:
    • If fuel pressure is within specification, go to step 3).
    • If fuel pressure is zero, go to step 5).
    • If fuel pressure is low, go to step 6).
    • If fuel pressure is high, go to FUEL PRESSURE REGULATOR.
      CAUTION: Inspect fuel system for leaks and damage before testing fuel pump.
  3. Check fuel injectors. See FUEL CONTROL. Start or crank engine. Using a mechanic's stethoscope, listen for regularly spaced operating clicks at each injector. If clicks are present, check fuel injectors for flow and leakage.
  4. If clicks are not present, check fuel injector resistance. See FUEL CONTROL. Replace injectors not within specification. If injectors are within specification, check for 12 volts at each injector lead. If voltage is present, circuit is okay. Clean or replace injectors as necessary. If voltage is not present at injectors, see CIRCUIT TEST H in G - EEC-IV TESTS W/CODES article in the ENGINE PERFORMANCE Section for circuit diagnosis.
  5. If fuel pressure is zero, ensure battery is fully charged. Ensure connection is okay at pump/sending unit. Turn ignition off. Using a jumper lead, ground FP terminal at Diagnostic Link Connector (DLC). See Fig 1. Turn ignition on, leaving engine off. Listen for sound of fuel pump. If pump is running, go to next step. If pump is not running, go to step 7).
    Fig 1: Identifying Fuel Pump Connector Terminals & Circuits
    G93F42114
  6. Check condition of fuel filter. Replace filter if necessary, and repeat step 1). If filter is okay, check fuel pressure regulator. See FUEL PRESSURE REGULATOR.
  7. Turn ignition off. Disconnect fuel pump/sending unit connector. Measure resistance between pump ground at connector and chassis ground. If resistance is greater than one ohm, repair open circuit to ground. If resistance is not greater than one ohm, go to next step.
  8. Ensure ignition is off and battery is fully charged. Disconnect harness connector from pump/sending unit. Ground FP terminal at DLC. Turn ignition on. Measure voltage at pump power terminal of pump/sending unit connector. If voltage is greater than 10.5 volts, replace pump/sending unit assembly. If voltage is not greater than 10.5 volts, go to next step.
  9. Check inertia switch. See ENGINE SENSORS & SWITCHES (PCM INPUTS). Check fuel pump relay (if equipped). See RELAYS under MODULES, RELAYS & SOLENOIDS. Check Constant Control Relay Module (CCRM) (if equipped). See MODULES under MODULES, RELAYS & SOLENOIDS. Check engine compartment for leaks and ensure engine produces normal engine vacuum. See FUEL PRESSURE REGULATOR.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.