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Home >> Mercury >> 1984 >> Capri GS, 3.8 3 >> Repair and Diagnosis >> Engine Performance >> System >> 3.8L CFI EEC IV Testing >> Testing >> Test Q - Fuel Control

Test Q - Fuel Control

NOTE: Fuel contaminated engine oil may affect 41 and 42 service codes. If this is suspected, remove PCV from valve cover and repeat Quick Test. If problem corrected, change engine oil and filter.
  1. Start and run engine for 2 minutes at 2000 RPM. With engine at normal operating temperature, perform Engine Running Self-Test. If codes 16, 17, 41, 42, 43, 48, or 91-98 present, go to next step. If these codes not present, repair all other codes as described in Engine Running Self-Test.
  2. Turn ignition off and wait 10 seconds. Disconnect 60-pin connector at ECA. Connect breakout box and reconnect ECA. With DVOM on 20 volt scale, connect leads between box pin 29 and pin 49. Install jumper wire from box pin 25 to pin 26. Deactivate Engine Running Self-Test. Start engine and stabilize speed at 1000-1200 RPM for 15 seconds. Observe DVOM while engine is running at 1000-1200 RPM. If reading is .5 volt or more go to step 4). If reading is less than .5 volt, go to next step.
  3. Turn ignition off and wait 10 seconds. Disconnect harness at left oxygen sensor. With DVOM on 20 volt scale, measure voltage from sensor connector to good ground (near sensor). Jumper wire installed between box pins 25 and 26 and Self-Test deactivated. Start engine and stabilize speed at 1000-1200 RPM for 15 seconds. Observe DVOM while engine is running at 1000-1200 RPM. If reading is .5 volt or more, remove jumper wire, reconnect sensor and go to step 14). If reading is less than .5 volt, go to step 5).
  4. Turn ignition off and wait 10 seconds. With DVOM on 20 volt scale, connect leads between box pin 43 and pin 44. Jumper wire installed between box pins 25 and 26 and Self-Test deactivated. Start engine and stabilize speed at 1000-1200 RPM for 15 seconds. Observe DVOM while engine is running at 1000-1200 RPM. If reading is .5 volt or more, go to step 14). If reading is less than .5 volt, go to step 6).
  5. Turn ignition off and wait 10 seconds. With DVOM on 20 volt scale, connect leads between box pin 43 and pin 44. Jumper wire installed between box pins 25 and 26 and Self-Test deactivated. Start engine and stabilize speed at 1000-1200 RPM for 15 seconds. Observe DVOM while engine is running at 1000-1200 RPM. If reading is .5 volt or more, replace left oxygen sensor and repeat Quick Test. If reading is less than .5 volt, remove jumper wire and go to step 12).
  6. Turn ignition off and wait 10 seconds. Disconnect harness at right oxygen sensor. With DVOM on 20 volt scale, measure voltage from sensor connector to good ground (near sensor). Jumper wire installed between box pins 25 and 26 and Self-Test deactivated. Start engine and stabilize speed at 1000-1200 RPM for 15 seconds. Observe DVOM while engine is running at 1000-1200 RPM. If reading is .5 volt or more, remove jumper wire, reconnect sensor and go to step 15). If reading is less than .5 volt, replace right oxygen sensor.
  7. Turn ignition off and wait 10 seconds. With DVOM on 20 volt scale, connect leads between box pin 29 and pin 49. Start engine and run at 2000 RPM for 30 seconds. Turn engine off and wait 10 seconds. Restart engine and observe DVOM. If reading stabilizes at .5 volt or less within 15 seconds, go to step 9). If reading does not stabilize at .5 volt or less within 15 seconds, go to next step.
  8. Turn ignition off and wait 10 seconds. Disconnect harness at left oxygen sensor. With DVOM on 20 volt scale, measure voltage from sensor connector to good ground (near sensor). Jumper wire installed between box pins 25 and 26 and Self-Test deactivated. Start engine and run at 2000 RPM for 30 seconds. Turn engine off and wait 10 seconds. Restart engine and observe DVOM. If reading stabilizes at .5 volt or less within 15 seconds, reconnect left oxygen sensor and go to step 14). If reading does not stabilize at .5 volt or less within 15 seconds, go to step 10).
  9. Turn ignition off and wait 10 seconds. With DVOM on 20 volt scale, connect leads between box pin 43 and pin 44. Self-Test deactivated. Start engine and run at 2000 RPM for 30 seconds. Turn engine off and wait 10 seconds. Restart engine and observe DVOM within 30 seconds of restart. If reading stabilizes at .5 volt or less within 30 seconds, replace ECA and retest. If reading does not stabilize at .5 volt or less within 30 seconds, replace right oxygen sensor and retest.
  10. Turn ignition off and wait 10 seconds. With DVOM on 20 volt scale, connect leads between box pin 43 and pin 44. Self-Test deactivated. Start engine and run at 2000 RPM for 30 seconds. Turn engine off and wait 10 seconds. Restart engine and observe DVOM within 30 seconds of restart. If reading stabilizes at .5 volt or less within 30 seconds, replace left oxygen sensor and retest. If reading does not stabilize at .5 volt or less within 30 seconds, go to next step.
  11. Turn ignition off and wait 10 seconds. Disconnect harness at right oxygen sensor. With DVOM on 20 volt scale, measure voltage from sensor connector to good ground (near sensor). Self-Test deactivated. Start engine and run at 2000 RPM for 30 seconds. Turn engine off and wait 10 seconds. Restart engine and observe DVOM within 30 seconds. If reading stabilizes at .5 volt or less within 30 seconds, reconnect right oxygen sensor and go to step 15). If reading does not stabilize at .5 volt or less within 30 seconds, turn engine off and go to step 13). Leave test equipment connected.
  12. Turn ignition off and wait 10 seconds. Remove DVOM and reconnect both oxygen sensors. Install jumper wire between box pin 25 and pin 26. Self-Test deactivated. Start engine and stabilize speed at 1500 RPM for 30 seconds. If black smoke present in exhaust flow, replace both oxygen sensors and retest. If black smoke not present, go to step 16).
  13. Turn ignition off and wait 10 seconds. Disconnect harness at right oxygen sensor. With DVOM on 20 volt scale, measure voltage from sensor connector to good ground (near sensor). Remove air cleaner cover. Start engine and wait 10 seconds. Then run engine at 2000 RPM for 60 seconds. Turn engine and ignition off. When engine stops, disconnect harness from both injectors. Hold accelerator pedal to floor and crank engine for 10 seconds while observing DVOM. If reading less than .5 volt, reconnect right oxygen sensor and go to step 16). If reading greater than .5 volt, replace both oxygen sensors and retest.
  14. Turn ignition off and wait 10 seconds. Disconnect harness at left oxygen sensor. With DVOM on 200 ohm scale, measure resistance from sensor connector to box pin 29. If reading less than 5 ohms, replace ECA and retest. If reading greater than 5 ohms, repair harness and retest.
  15. Turn ignition off and wait 10 seconds. Disconnect harness at right oxygen sensor. With DVOM on 200 ohm scale, measure resistance from sensor connector to box pin 43. If reading less than 5 ohms, replace ECA and retest. If reading greater than 5 ohms, repair harness and retest.
  16. Install fuel pressure gauge. Start and run engine and observe pressure. If engine will not run, cycle ignition from off to on several times and observe pressure gauge. If pressure is 35-45 psi (2.5-3.2 kg/cm2 ) with engine running or 60 seconds after final ignition off, go to next step. If pressure is not within specifications, check electric fuel pump(s).
  17. Repeat step 16) and observe pressure reading 2 minutes after stopping engine (last ignition off). If pressure drop is 4 psi (.3 kg/cm2 ) or less, go to next step. If pressure drop is greater than 4 psi (.3 kg/cm2 ), service fuel system.
  18. Disconnect harness at left injector. With fuel system pressurized, disconnect fuel pump relay or inertia switch to disable fuel pump. Crank engine for 2 seconds and observe pressure gauge. Turn ignition off. Wait 5 seconds and observe pressure drop. If pressure drops 2-16 psi (.1-1.1 kg/cm2 ), go to next step. If pressure drop is not 2-16 psi (.1-1-1 kg/cm2 ), go to step 22).
  19. Reactivate fuel pump and reconnect left injector. Disconnect harness at right injector. Repeat step 18) for right injector. If pressure drops 2-16 psi (.1-1.1 kg/cm2 ), go to next step. If pressure drop is not 2-16 psi (.1-1.1 kg/cm2 ), go to step 22).
  20. Reactivate fuel pump and reconnect right injector. Start engine and allow to idle. Observe pressure gauge. If pressure is 35-45 psi (2.5-3.2 kg/cm2 ), go to next step. If pressure is not 35-45 psi (2.5-3.2 kg/cm2 ), check fuel supply system.
  21. Connect tachometer to engine. Disconnect and plug vacuum hose at EGR valve. Start and run engine at 2000 RPM. It may be necessary to disconnect harness at idle speed control motor and set speed by using throttle body stop screw. Disconnect harness at left injector and note RPM when engine stabilizes. Reconnect left injector and stabilize engine speed at 2000 RPM. Disconnect harness at right injector and note RPM when engine stabilizes. Reconnect right injector and stabilize engine speed at 2000 RPM. Note difference between both readings. If reading dropped at least 150 RPM for each injector, fuel system okay. Reconnect EGR vacuum hose and check other causes for problem (fouled plugs, fuel-in-oil, etc.). If reading did not drop 150 RPM for each injector, reconnect EGR vacuum hose and replace both injectors.
  22. Turn ignition off and wait 10 seconds. Disconnect harness at both injectors and switch harness connections (left harness to right injector, right harness to left injector). Perform Engine Running Self-Test. If suspected injector still fails, replace faulty injector, restore harness connections to proper injectors and retest. If suspected injector does not fail, go to next step.
  23. Turn ignition off and wait 10 seconds. Disconnect harness at both injectors. With DVOM on 20 volt scale, measure voltage from both injector harness connectors to ground. If both readings less than 1 volt, reconnect injectors and go to next step. If either reading greater than 1 volt, repair short and retest.
  24. Turn ignition off and wait 10 seconds. Breakout box installed and ECA and injectors connected. With DVOM on 200 ohm scale, measure resistance from box pin 60 to pin 58 (left injector) and from box pin 60 to pin 59 (right injector). If readings less than 5 ohms, go to next step. If readings greater than 5 ohms, go to step 27).
  25. Disconnect harness at throttle body and both injectors. With DVOM on 200 ohm scale, measure resistance from injector 1 of throttle body harness to ground and note reading. Repeat for injector 2. If reading on either or both injectors less than 5 ohms, repair short or replace injector. If reading on either or both injectors is greater than 5 ohms, go to next step.
  26. Harness disconnected from throttle body. Disconnect ECA from breakout box. With DVOM on 200 ohm scale, measure resistance from box pin 58 to injector 1 of throttle body harness. Repeat from box pin 59 to injector 2 of throttle body harness. If either or both readings less than 5 ohms, repair short and retest. If either or both readings greater than 5 ohms, replace ECA.
  27. Harness disconnected at both injectors. With DVOM on 200 ohm scale, measure resistance across terminals of each injector. If reading less than 1.5 ohms or greater than 2.5 ohms, replace injector and retest. If reading is not less than 1.5 ohms or not greater than 2.5 ohms, go to next step.
  28. Harness disconnected at throttle body and both injectors and ECA disconnected. With DVOM on 200 ohm scale, measure resistance from box pin 58 to injector 1 and from box pin 59 to injector 2. If reading less than 2 ohms, reconnect harness at throttle body. Reconnect ECA to breakout box and go to next step. If reading greater than 2 ohms, repair harness and retest.
  29. Breakout box installed and ECA and throttle body harness connected. Harness disconnected at both injectors. With DVOM on 200,000 ohm scale, measure resistance from box pin 58 to pin 59. If reading less than 10,000 ohms, go to next step. If resistance greater than 10,000 ohms, replace ECA and retest.
  30. Harness disconnected from injectors and throttle body. Breakout box installed and ECA disconnected. With DVOM on 200,000 ohm scale, measure resistance from injector 1 to injector 2 at throttle body harness. If resistance less than 10,000 ohms, repair short and retest. If resistance greater than 10,000 ohms, replace ECA.
Fig 1: Throttle Body Wiring Diagram for 10-Pin Connector
G21649
Fig 2: Throttle Body Wiring Diagram for Separate Connectors
G1168
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