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Home › Lincoln › 1986 › Mark VII Base › Repair and Diagnosis › Engine Performance › System › 5.0L SEFI EEC IV Testing › Circuit Tests › Test S - Fuel Control

Test S - Fuel Control

NOTE: See HOW TO USE CIRCUIT TESTS  before performing this test. Fuel contaminated engine oil may affect service codes 41, 42, 91 and 92. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST  . If problem is corrected, change engine oil and filter. Enter CYLINDER BALANCE TEST as specified in step 1). For additional information see QUICK  TEST DIAGNOSTIC AIDS, CYLINDER BALANCE TEST  in front of this article.
  1. Perform KEY ON/ENGINE RUNNING (KOER) SELF-TEST  and enter CYLINDER BALANCE TEST  by briefly opening throttle (one second) to wide open throttle (WOT) immediately after last service code is displayed. If balance test does not display code 90, go to step 4). If balance test displays code 90 (Pass), go to step 10).
  2. Turn key off and wait 10 seconds. Install fuel pressure gauge. Start and run engine. Fuel pressure must be 35-45 psi (2.5-3.2 kg/cm2 ). Pressure must remain at 35-45 psi (2.5-3.2 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 pump does not hold pressure for 60 seconds, go to step 1). If fuel pressure is correct, go to next step.
  3. With key off and pressure gauge installed, cycle key from off to on a few times to pressurize system. Locate and disconnect fuel pump relay. Crank engine for 5 seconds and take pressure reading immediately after cranking. If pressure reading is 10-20 psi (0.7-1.4 kg/cm2 ) after cranking, EEC system is NOT at fault for no start. If problem is rough running, missing, or fuel code, go to next step. If pressure is incorrect, go to step 5).
    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 (0.7 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).
  4. Turn key off. Perform ENGINE RUNNING SELF-TEST and enter CYLINDER BALANCE TEST  by briefly opening throttle (one second) to wide open throttle (WOT) immediately after last service code is displayed. If balance test displays code 90 (Pass), go to DIAGNOSIS BY SYMPTOM TEST  . If balance test does not display code 90, go to next step.
    CYLINDER BALANCE TEST SERVICE CODES

    Code Cylinder/Injector No. Breakout Box Pin No.
    90 Pass Pass
    10 1 58
    20 2 59
    30 3 12
    40 4 13
    50 5 14
    60 6 15
    70 7 42
    80 8 52
    77 Retest Retest
  5. Turn key off and disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale and measure resistance between suspect injector circuit test pin and test pins 37 and 57. If reading is not between 15 and 19 ohms, repair open in harness/connectors on suspect injector circuit. If circuit is okay, replace injector and repeat QUICK TEST  . If reading is between 15 and 19 ohms, go to next step.
  6. With key off, breakout box installed and ECA disconnected, set DVOM on 200,000-ohm scale. Measure resistance between suspect injector circuit test pin and test pins 40 and 60. If reading is less than 10,000 ohms, repair short to ground and repeat QUICK TEST  . If resistance is 10,000 ohms or more, go to next step.
  7. With key off and breakout box installed, connect ECA to breakout box. Connect a non-powered 12-volt test lamp between test pin 37 and suspect injector circuit test pin(s). Crank or start engine. If test lamp glows dimly, replace injector and repeat QUICK TEST  and CYLINDER BALANCE TEST  . If test lamp is bright or does not light, replace ECA. Repeat QUICK TEST  and CYLINDER BALANCE TEST  .
    NOTE: Vacuum/air leaks in the following non-EEC related areas may cause code 41 or 91 to be displayed. Check for leaking A/C vacuum actuator and engine vacuum leaks. Check EGR and PCV systems. Check for air leak between airflow and throttle body. Check for contaminated HEGO sensor(s). Code 41 is for left HEGO, code 91 is for right HEGO. Both codes indicate an always lean condition.
  8. Code 41 or 91 Displayed. Turn key off and set DVOM on 20 volt scale. Disconnect appropriate HEGO sensor from vehicle harness. Connect DVOM to HEGO sensor and engine ground. Apply 14 in. Hg to manifold absolute pressure (MAP) sensor and start engine. If reading is less than 0.5-volts, replace HEGO sensor(s) then repeat QUICK TEST  . If reading is more than 0.5-volts, go to next step.
  9. Turn key off. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale and measure resistance between test pin 49 and engine block ground. Measure resistance between test pin 29 and HEGO signal at vehicle harness connector and/or measure resistance between test pin 43 and HEGO signal at vehicle harness connector. If all readings are higher than 5 ohms, repair open in appropriate circuit and repeat QUICK TEST  . If all readings are less than 5 ohms, go to next step.
  10. With key off, breakout box installed and ECA disconnected, set DVOM on 200,000-ohm scale. Measure resistance between test pin 29 (right HEGO) and test pin 40 and/or between test pin 43 (left HEGO) and test pin 40. If any reading is less than 10,000 ohms, correct cause of resistance to ground. Repeat QUICK TEST  . If reading is 10,000 ohms or higher, go to next step.
  11. With key off, breakout box installed, ECA disconnected, and DVOM on 200,000-ohm scale, disconnect appropriate HEGO sensor. Measure resistance between HEGO signal and HEGO ground circuit at HEGO sensor connector. If reading is 10,000-ohms or higher, start and run engine at 2000 RPM for 2 minutes. Repeat QUICK TEST  . If code 41 or 91 are still displayed, replace ECA. If code 41 or 91 are not displayed, go to step 14). If reading is 10,000 ohms or less, replace appropriate HEGO sensor and repeat QUICK TEST  .
    Fig 1: 5.0 SEFI Fuel Control Circuits
    G4274
  12. Code 42 or 92 Displayed. These codes indicate an always rich condition. The following non-EEC areas may cause codes 42 or 92 to be displayed: Check for fuel contaminated engine oil, ignition caused misfire, or CANP problems. Turn key off and wait 10 seconds. Disconnect vehicle harness at HEGO sensor. Using a jumper wire, ground vehicle harness HEGO circuit to engine block. Repeat ENGINE RUNNING SELF-TEST. If codes 41 or 91 are displayed, replace HEGO sensor and repeat QUICK TEST  . If codes 42 or 92 are displayed, go to step 2). If codes 41 or 91 are not displayed, go to next step.
  13. Turn key off and wait 10 seconds. Install breakout box and measure resistance between test pin 49 (HEGO ground) and engine block. Measure resistance between test pin 43 and HEGO vehicle harness connector for code 42. Measure resistance between test pin 29 and HEGO vehicle harness connector for code 92. If all readings are less than 5 ohms, disconnect ECA. Inspect for and repair any damaged wiring. If ECA connector is okay, replace ECA and repeat QUICK TEST  . If any reading is more than 5 ohms, repair circuit having a resistance higher than 5 ohms, then repeat QUICK TEST  .
  14. Turn key and engine off. Set DVOM on 200-ohm scale and measure resistance between run circuit and ground at both HEGO sensor connectors (at room temperature). If either reading is less than 2.5 ohms or higher than 5 ohms, replace appropriate HEGO sensor and repeat QUICK TEST  . If both readings are between 2.5 and 5 ohms, go to next step.
  15. Turn key on, leave engine off. Set DVOM on 20-volt scale and connect positive test lead to run circuit and negative test lead to ground at both HEGO vehicle harness connectors. If both readings are 10.5-volts or higher, HEGO sensor system is okay, and the EEC system is not at fault. If either reading is less than 10.5-volts, go to next step.
  16. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale and measure resistance of both ground circuits from HEGO sensor connectors to negative battery post (ground). If any reading is less than 5 ohms, repair open in run circuit and repeat QUICK TEST  . If any reading is 5 ohms or more, repair open in ground circuit and repeat QUICK TEST  .
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