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Home >> Ford >> 1995 >> Explorer 4D Utility, 4WD, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests - EEC-IV (4.0L) >> Fuel System >> Fuel Delivery >> Fuel Pump Relay
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Fuel Pump Relay

See RELAYS  under RELAYS & SOLENOIDS.

CAUTION: Inspect fuel system for leaks and damage before testing fuel pump.
  1. System Integrity Check  Perform the following checks:
    • Ensure Inertia Fuel Shutoff (IFS) switch reset button is not in upper (tripped) position. On Aerostar, IFS switch is located below right side of instrument panel, behind trim panel. On Explorer, IFS switch is located under instrument panel, near right side of transmission hump.
    • Ensure battery is fully charged and fuel-related fuses are okay.
    • Check fuel tank contents and fuel gauge accuracy. On vehicles with 2 fuel tanks, check both tanks. If any fault is detected, repair as necessary. If system checks are okay, go to next step.
  2. Check Fuel Pressure  Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  . Install fuel pressure gauge. Connect a jumper wire between ground and fuel pump test terminal at Data Link Connector (DLC). See Fig 1 .Turn ignition on to activate pump. Check and record fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. Proceed to appropriate step.
    • If fuel pressure is within specification, go to next step.
    • If fuel pressure is low, go to step 10).
    • If fuel pressure is high, go to step 11).
      Fig 1: Data Link Connector Terminal ID (Aerostar & Explorer)
      G93H40433
  3. Check For Fuel Pressure Leak-Down  Operate fuel pump as in step 2) for a minimum of 30 seconds. Turn ignition off, and disconnect jumper wire from DLC. Wait one minute then check fuel pressure gauge. If fuel pressure remains within 5 psi (34 kPa) of specification, go to step 5). If fuel pressure does not remain within 5 psi of specification, go to next step.
  4. Check Fuel Pressure Regulator Diaphragm  Turn ignition off. Ensure vacuum hose is connected to fuel pressure regulator. Start and run engine for 10 seconds. Stop engine, and wait 10 seconds. Start and run engine for 10 seconds. Stop engine. Remove vacuum hose from pressure regulator. If fuel is present in vacuum port, replace fuel pressure regulator, and repeat step 2). If fuel is not present, either fuel injectors are leaking down or check valve in fuel pump is defective. Repair as necessary and repeat step 2).
  5. Check Fuel Pressure With Engine Load  Ensure vacuum hose is still disconnected from pressure regulator. Observe pressure gauge while driving vehicle with heavy accelerations. If vehicle is equipped with 2 fuel tanks, perform test on both tanks. If fuel pressure remains within 3 psi during test, reconnect vacuum hose to pressure regulator and go to next step. If fuel pressure does not remain within 3 psi, go to step 8).
  6. Check Fuel Pressure Regulator  Install vacuum gauge to intake manifold. Start engine. Observe vacuum and fuel pressure gauge while accelerating and decelerating engine. When engine is accelerating, vacuum reading should decrease and fuel system pressure should increase. When engine is decelerating, vacuum reading should increase and fuel system pressure should decrease. If readings are as specified, fuel system is okay and test is compete. If gauge readings are not as specified, go to next step.
  7. Check Vacuum Supply  Disconnect and plug fuel pressure regulator hose. Attach vacuum pump to fuel pressure regulator. Start engine. Apply vacuum to pressure regulator while observing fuel pressure gauge. If fuel pressure changes as vacuum changes, repair restriction in vacuum supply hose. If fuel pressure does not change as vacuum changes, replace fuel pressure regulator.
  8. Check Fuel Filter  Check for plugged fuel filter. Replace filter as necessary. Pressurize fuel system as in step 2), and check fuel pressure. If fuel pressure is as specified, repeat step 3). For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article.If fuel pressure is not as specified, go to next step.
  9. Turn ignition on. Disconnect harness connector from pump/sender unit. Ground terminal FP at Data Link Connector (DLC). With DVOM on 20-volt scale, measure voltage to fuel pump. If battery voltage is not present, locate and repair cause of low voltage and repeat step 2). If battery voltage is present, check fuel pump ground connection. Repair as necessary. If ground is okay, replace fuel pump.
  10. Check For Low Pressure Causes  Turn ignition off. Release fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE  . Disconnect fuel return hose from pressure regulator. Using a separate piece of fuel hose, connect one end of hose to fuel return port at pressure regulator and place other end of hose into a suitable container. With jumper wire still connected to DLC as in step 2), turn ignition on (engine off). If fuel pressure is still low and fuel is being returned to container, replace pressure regulator. If fuel pressure is still low and fuel is not being returned to container, replace fuel pump and repeat step 2).
  11. Check For High Pressure Causes  Turn ignition off. Release fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE  . Disconnect fuel return hose from pressure regulator. Using a separate piece of fuel hose, connect one end of hose to fuel return port at pressure regulator and place other end of hose into a suitable container. With jumper wire still connected to DLC as in step 2), turn ignition on (engine off). If fuel pressure is within specification, replace pressure regulator and repeat step 2). For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is not within specification, go to next step (models with 2 fuel tanks) or step 13) (models with one fuel tank).
  12. Check Fuel Return System (Models With 2 Tanks)  Turn ignition off. Check fuel return lines for blockage, kinking and pinching. If only one tank is affected, pay close attention to return line between "Y" in return line and affected tank. If both tanks are affected, check return line between pressure regulator and "Y" in fuel return line. Repair as necessary. If fuel return lines are okay, ensure fuel return hose is still disconnected at pressure regulator. Disconnect fuel return hose near fuel tank. Apply 3-5 psi of regulated air to return line port at pressure regulator. If air flows freely through return line, replace Fuel Delivery Assembly (FDA) and repeat step 2). If air does not flow freely, check fuel return system for restrictions. Repair as necessary and repeat step 2).
  13. Check Fuel Return System (Models With One Tank)  Turn ignition off. Fuel return hose should still be disconnected at pressure regulator. Disconnect fuel return hose near fuel tank. Apply 3-5 psi of regulated air to return line port at pressure regulator. If air flows freely through return line, replace fuel pump and repeat step 2). If air does not flow freely, check fuel return system for restrictions. Repair as necessary and repeat step 2).
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