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Test S - CFI Fuel Control

NOTE: Fuel contaminated engine oil may affect 41, 42 and 43 service codes. If this is suspected, remove PCV from valve cover and repeat QUICK TEST. If problem corrected, change engine oil and filter.
  1. 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 25-25 psi (2.5-2.5 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. Set DVOM to 200 ohm range. Disconnect ECA 60-pin connector and inspect for damage, corrosion or loose wires. Service as necessary. Install breakout box, leaving ECA disconnected. Measure resistance between test pins 57 and 58 and between tests pins 57 and 59. If resistance is less than 1.5 ohms or greater than 3.5 ohms, service the harness/connectors on the suspect injector for opens or shorts. If okay, replace injector. If resistance is 1.5 to 3.5 ohms, go to next step.
  4. 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.
  5. 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.
  6. Turn key OFF. Set DVOM to 20 volt scale. Disconnect EGO sensor from vehicle harness. Connect DVOM to EGO sensor and ground. Disconnect ACT sensor. Start engine and run at about 2000 RPM. If DVOM reading is greater than .5 volt within 1 minute, go to next step. If not, replace EGO sensor and repeat QUICK TEST.
  7. Turn key OFF and wait 10 seconds. Disconnect ECA 60-pin connector and inspect for damage, corrosion or loose wires. Service as necessary. Install breakout box, leave ECA disconnected. Measure resistance between test pin 49 and engine block and between EGO sensor connector and test pin 29. If both circuits are less than 5 ohms, go to next step. If not, service as necessary and repeat Quick Test.
  8. With key OFF, ECA disconnected and breakout box installed, 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.
  9. Turn key OFF. Reconnect EGO sensor. Make certain that the ACT sensor is still disconnected. Start engine and run at about 2000 RPM for 1 minute. Return to idle. Perform Engine Running Self-Test. If code 41, inspect for corrosion or damaged pins. If okay, replace ECA and repeat QUICK TEST. If code 41 is not present, EGO sensor is okay. Reconnect ATC and go to step 1).
  10. Always rich condition. Turn key OFF and wait 10 seconds. Check for fuel contaminated engine oil, ignition caused misfire and CANP problems. Disconnect vehicle harness at the EGO sensor. Using a jumper wire, ground vehicle harness EGO circuit at the EGO sensor to the engine block. Repeat Engine Running Self-Test. If code 41, go to step 12). If not, go to step 11).
  11. Turn key OFF and wait 10 seconds. Disconnect ECA 60-pin connector and inspect for damage, corrosion or loose wires. Service as necessary. Install breakout box. Measure resistance between test pin 49 and EGO ground at engine block and between EGO harness connector and test pin 29. If both circuits are less than 5 ohms, disconnect ECA and inspect. If okay, replace ECA and repeat Quick Test. If both circuits are greater than 5 ohms, correct harness circuit with resistance greater than 5 ohms and repeat QUICK TEST.
  12. EGO Check. Set DVOM to 20 volt scale. With EGO sensor disconnected from the harness, connect the DVOM from EGO sensor to engine ground. Disconnect PCV hose. Start engine and run at 2000 RPM. If the DVOM reading is less than .4 volt within 1 minute the EGO sensor is okay. Go to step 1). If not, replace EGO sensor and repeat QUICK TEST.
  13. 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.
  14. Turn key OFF. Set DVOM to 200 ohm scale Measure resistance between Run circuit and ground on heated EGO connector at room temperature. If reading is between 2.5 and 5.0 ohms, go to next step. If reading is less than 2.5 ohms or greater than 5.0 ohms, replace HEGO sensor.
  15. Turn key OFF. Set DVOM to 20 volt scale. Connect positive lead to run circuit and negative lead to ground on HEGO harness connector. If reading is 10.5 volts or greater, HEGO sensor system is okay. If reading is less than 10.5 volts, go to next step.
  16. Turn key OFF and wait 10 seconds. Set DVOM to 200 ohm scale. Measure resistance of ground circuit between HEGO connector and battery ground. If reading is less than 5 ohms, service open in run circuit. If reading is 5 ohms or greater, service open in ground circuit.
  17. Code 43 Displayed. Run engine at 2000 RPM for 2 minutes. Turn key OFF and wait 10 seconds. Perform Engine Running Self-Test. If code 43, go to next step. If not, service other codes as necessary.
  18. Code 43 Displayed. Check exhaust leaks at manifold or inlet pipe. If there are leaks, service and repeat QUICK TEST. If no leaks, go to next step.
  19. Code 43 Displayed. Start engine and let idle. If engine idle quality is poor during and after Quick Test, adjust idle speeds. If not, replace EGO sensor and repeat QUICK TEST.
Fig 1: 5.0L CFI Fuel Control Circuits
G2560
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