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HOMESERVICE MANUALSFORD1985THUNDERBIRD BASE, 2.3 W, AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSIS1.6L & 2.3L EFI/TURBO TESTSTESTINGTEST Q - EFI FUEL CONTROL
1985 Ford Thunderbird Base, 2.3 W, Automatic

Test Q - EFI Fuel Control

1985 Ford Thunderbird Base, 2.3 W, AutomaticSECTION Test Q - EFI Fuel Control
CAUTION: On next step, and on all steps involving fuel testing, turn key OFF immediately if any fuel leaks develop. DO NOT  allow any smoking or open flame in area of vehicle being tested.
  1. Turn key OFF and wait 10 seconds. Install fuel pressure gauge. Start and run engine. Fuel pressure must be 25-45 psi (1.8-3.2 kg/cm2 ). Pressure must remain at 25-25 psi (1.8-2.5 kg/cm2 ) for 60 seconds after key is turned OFF. If engine has a "No Start" problem, cycling the key from OFF to ON a few times will build up fuel pressure. If fuel pressure is outside range, check electric fuel pump and fuel pressure regulator. If fuel pressure is correct, go to next step.
  2. With pressure gauge installed, cycle key from OFF to ON a few times to pressurize system. Disconnect fuel pump relay. Crank engine for 5 seconds and take pressure reading immediately after finishing cranking. If pressure reading is 10-20 psi (.7-1.4 kg/cm2 ) after 5 seconds of cranking, EEC system is not at fault for no start. If problem is rough running, missing, fuel code, or pressure is incorrect after 5 second crank, go to next step.
    NOTE: Make sure that fuel is of good quality and not contaminated by air or water as pressure readings may be incorrect with bad or contaminated fuel. Also, pressure drop will be greater when engine is cold than when engine is warm. If coolant is 200°F (93°C) pressure should drop approximately 10 psi (.7 kg/cm2 ) in 5 seconds while a pressure drop of 20 psi (1.4 kg/cm2 ) should occur in 5 seconds with engine coolant at 60°F (15.6°C).
  3. Turn key OFF and wait 10 seconds. Disconnect ECA 60-pin connector and check for loose wires and damaged or corroded pins. Repair connector and connect breakout box, leaving ECA disconnected. Set DVOM to 200 ohm scale. Measure resistance through harness between test pins 37 and 58 for injector bank 1. Measure resistance through harness between test pins 37 and 59 for injector bank 2. If both readings are between 1.2-1.8 ohms, go to step 5). If both readings are not between 1.2-1.8 ohms, go to next step.
  4. With key OFF and ECA disconnected, set DVOM to 200 ohm scale. Disconnect all injectors on bank to be tested. Connect each injector individually and test resistance between test pins 37 and 58 for bank 1 or between test pins 37 and 59 for bank 2. If all readings are not between 2.0-2.7 ohms, check harness and connectors on injector for shorted or open circuits. If circuits are alright, replace injector in question and repeat QUICK TEST  . If all readings are between 2.0-2.7 ohms, go to next step.
  5. With key OFF, reconnect ECA through breakout box. Reconnect all injectors. Connect non-powered 12 volt test light between test pins 37 and 58. Crank or start engine. Repeat procedure with test light between test pins 37 and 59. If test light does not come on during either or both tests, check for 12 volt battery power at test pins 37 and 57. If test pins 37 and 57 have 12 volt power, replace ECA and repeat QUICK TEST  . If test light is very bright on either or both tests, check circuits to banks 1 and 2 for short to ground. If no short is found, replace ECA and repeat QUICK TEST  . If test light glows dimly on both tests, go to next step.
  6. Connect tachometer and run engine at steady 2000 RPM. Disconnect ISC and use throttle stop screw to set speed if necessary. Disconnect and reconnect one injector at a time and note RPM drop for each injector. Reset curb idle and verify ISC hookup (using VECI decal) at end of test procedure. If each injector does not produce at least 150 RPM drop when disconnected, replace faulty injector(s) and repeat QUICK TEST  . If RPM drop is correct for all injectors, running or driving problem is in an area common to all cylinders such as a vacuum leak or fuel contamination.
    NOTE: Areas other than EEC may cause service codes 41 and 42 to be displayed. Check for ignition caused misfires, CANP problems, or engine oil that is contaminated by fuel if service code 42 is displayed. If fuel contamination is suspected, repeat QUICK TEST  after removing PCV from valve cover. If this resolves problem, replace engine oil and oil filter. Check for leaking vacuum motor, engine sealing problem, faulty EGR or PCV systems, unmetered air leak between air meter and throttle body, or a lead contaminated EGO sensor if service code 41 is displayed.
  7. Code 42 Displayed. This code indicates an "always rich" condition. See note prior to this step before starting test. With key OFF, wait 10 seconds. Disconnect vehicle harness at EGO (oxygen) sensor. Ground the EGO sensor connector at engine block with a jumper wire. Repeat Engine Running Self-Test. If service code 41 results, go to step 9). If service code 41 does not result, go to next step.
  8. Turn key OFF and wait 10 seconds. Connect breakout box. Measure resistance of EGO sensor ground circuit between EGO sensor ground on block and test pin 49. Measure resistance of EGO sensor circuit between EGO sensor harness connector and test pin 29. If both circuits have less than 5 ohms resistance, disconnect ECA connector and inspect for damage or corrosion. If connector looks good, replace ECA and repeat QUICK TEST  . If both circuits tested do not have less than 5 ohms resistance, repair circuit with excessive resistance and repeat QUICK TEST  .
  9. Set DVOM to 20 volt scale. Disconnect EGO sensor from harness and connect DVOM between EGO sensor and engine ground. Start engine and run at 2000 RPM for 1 minute. Observe DVOM reading while disconnecting intake manifold vacuum hose. See Figure . If DVOM reads .4 volts or higher, replace EGO sensor and repeat QUICK TEST  . If DVOM reads less than .4 volts, go to step 1) of this test.
    Fig 1: Intake Manifold Hose Removal For Test
    G4271
  10. Code 41 Displayed. This code indicates an "always lean" condition. See note prior to step 7) before starting test. With key OFF and DVOM set to 20 volt scale, disconnect EGO sensor from harness. Connect DVOM between EGO sensor and engine ground. Remove air cleaner in order to reach airflow meter inlet. Use wood pencil to prop air meter door in partially open position. Start engine and run at 2000 RPM for 2 minutes. If DVOM does not read higher than .5 volts after 1 minute, replace EGO sensor and repeat QUICK TEST  . If DVOM reads higher than .5 volts after 1 minute, go to next step.
  11. Turn key OFF and connect breakout box. Leave ECA disconnected. Measure resistance of EGO sensor circuit between engine block ground and test pin 49. Measure resistance of EGO sensor circuit between EGO sensor connector and test pin 29. If either or both circuits show 5 ohms or greater, repair wiring and repeat QUICK TEST  . If both circuits show less than 5 ohms resistance, go to next step.
  12. With key OFF and ECA disconnected, set DVOM to 200,000 ohm scale. Measure resistance between test pins 29 and 40. If reading is less than 10,000 ohms, correct cause of resistance to ground and repeat QUICK TEST  . If resistance is 10,000 ohms or higher, go to next step.
  13. With key OFF, reconnect EGO sensor. Remove air cleaner and prop airflow meter door partially open with wood pencil. Start engine and run at 2000 RPM for 2 minutes. If code 41 is displayed, check for corrosion or damaged pins. Replace ECA if connector appears to be good. Repeat QUICK TEST  . If code 41 is not displayed, EGO sensor input circuit is good. Proceed to step 1) of this test.
  14. Continuous Codes 41 & 42 Displayed. If code 41 appears it indicates that the fuel system was lean for more than 15 seconds, when it should have been under control of EGO sensor. If code 42 appears, it indicates that the fuel system was rich for more than 15 seconds, when it should have been under control of EGO sensor. Before attempting to correct a code 41 or 42, first diagnose all other complaints such as rough idle or missing. Areas to check to isolate fuel control problems are as follows:
    • Unmetered Air. Vacuum or intake air leaks in canister purge system, PCV, engine sealing or air leaks between airflow meter and throttle body.
    • EGO Sensor Fuel Fouled. If fuel fouled spark plugs are observed, make complete check of ignition system. If EGO sensor is fuel fouled (low output and/or slow response), run vehicle at high (but legal) sustained speeds. Follow speed run with a few hard accelerations to burn off contamination and restore EGO sensor to correct operation.
    • Fuel Pressure. Perform step 1) in this test.
    • Ignition System. If always in default spark (10 degrees), perform Computed Ignition Timing Check.
    • Improper Fueling. Lead fouled EGO sensor.
    • TPS. If not moving, check for mechanical damage. Connect DVOM to test pins 47 and 46. Turn key ON, leaving engine OFF. Observe DVOM while moving throttle. Reading must increase with throttle opening. If not, replace TPS as required. If, at this point, drive problem is still present, perform steps 2) through 5) only.
Fig 2: EFI Fuel Control Circuits
G2558
RENDER: 1.0x

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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.