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Home >> Ford >> 1986 >> Thunderbird Base, 5.0 F >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Injection System - Multi-Point >> Testing >> Fuel Delivery System >> 2.3L Turbo, 3.0L & 5.0L
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2.3L Turbo, 3.0L & 5.0L

  1. Check fuel tank for sufficient fuel supply. Check for fuel leakage at all fittings and lines. Using volt-ohmmeter (VOM), check fuel pump electrical circuit for voltage supply and continuity.
  2. On Town Car, Crown Victoria and Grand Marquis models, disconnect fuel pump electrical connector just forward of fuel tank. On Mark VII, Continental, Thunderbird, Cougar, Mustang and Capri models, disconnect fuel pump power supply wire at fuel pump relay or grommet in trunk. On LTD and Marquis models, disconnect electrical connector to fuel pumps at high pressure pump module.
  3. On Mark VII, Continental, Thunderbird, Cougar, Mustang and Capri models, connect VOM between chassis ground and power supply wire with ignition off. If reading is 5 ohms or less, go to step 5). If reading is too high, attach ground lead of VOM to ground lead of pump circuit. If reading is now correct, check body ground or wiring between fuel pump and body ground.
  4. If reading still too high, remove fuel tank and check for continuity across fuel pump terminals. If continuity is shown, check wiring. If no continuity, change fuel pump.
  5. On all models, connect VOM to body wiring harness connector. Turn ignition on while watching voltmeter. Reading should rise to battery voltage then return to 0 volts after approximately 1 second. If not as specified, check inertia switch and electrical system.
  6. On LTD and Marquis models, connect VOM to pump wiring harness connector. If no continuity is present, check continuity directly at high pressure pump terminals. If no continuity at pump terminals, replace pump. If continuity is present at pump, service and replace wiring harness.
  7. To check low pressure pump, connect VOM across body wiring harness connector. If continuity (5 ohms or less) is present, low pressure pump circuit is electrically okay. If no continuity is present, remove fuel tank. Check for continuity at fuel pump/pump sender flange terminals. If no continuity is present, replace assembly. If continuity is present at pump but not at harness connector, service or replace wiring harness to low pressure pump.
  8. On all models, check fuel pump pressure and delivery volume. Disconnect fuel return line at fuel rail, using care to avoid spillage. Connect hose from fuel rail fitting to calibrated container holding at least 1 quart. Connect fuel pressure gauge to fuel pressure relief valve.
  9. Remove fuel pump relay and install modified fuel pump relay. See MODIFYING FUEL PUMP RELAY  procedure. Take extended ground lead to convenient location on vehicle. Ground extended lead to activate fuel pump for 10 seconds. Observe pressure while activated.
  10. Check delivery volume after all fuel has drained from hose into container. Fuel pump is operating properly if fuel pressure reaches 35-45 psi (2.5-3.2 kg/cm2 ), delivery volume is minimum of 8.1 ozs. (.24L) for 10 seconds, and residual pressure holds at minimum of 30.0 psi (2.1 kg/cm2 ) immediately after pump is shut off.
  11. If all 3 conditions are met, fuel pump is operating normally. Check for engine and electrical problems. If pressure is good but volume is not, check for restricted filters or supply lines. After correcting any blockage, recheck. If volume requirements are still not met, replace fuel pump.
  12. If both delivery pressure and volume requirements are met, but residual pressure does not hold, check for leaking regulator or injectors. If both test good, replace fuel pump/sending unit. If no flow or pressure is seen, fuel system should be checked as in step 11). If no trouble is found, replace fuel pump/sending unit.
  13. On LTD and Marquis models, check low pressure in-tank pump if hot fuel problems exist or system is noisy. Remove inlet push connect fitting and line from high pressure pump assembly. Raise end of fitting above level of fluid in tank to prevent siphon action.
  14. Connect hose from fuel tank to calibrated container holding at least 1 quart. Turn ignition on until fuel pump times out (approximately 1 second). Check container for presence of fuel (if necessary, lift container to prevent siphon action). Amount of fuel should be minimum of 1.5 oz. (.04L) for 1 second of operation.
  15. If no fuel is delivered, repeat timing out of fuel pump, twice or 3 times if necessary. If fuel still is not delivered, check for pinched line between fuel tank and fitting. If lines not pinched, remove fuel tank. Connect VOM to chassis electrical connector from fuel pump and turn ignition on. Reading should rise to battery voltage for 1 second and then return to 0 volts.
  16. If reading is correct and electrical connector was okay at pump, replace fuel pump assembly. Repeat low pressure fuel pump test. If no voltage is present, repair electrical circuit in vehicle. If pump tests correctly but sounds noisy, high pressure pump may be at fault.
  17. Check inlet and outlet pipes at high pressure pump for vibration during operation. If either line has much greater level of vibration than the other, change high pressure pump. Recheck for vibration and noise while operating.
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