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Home >> Merkur >> 1985 >> XR4Ti Standard >> Repair and Diagnosis >> Engine Performance >> System >> EEC IV System >> Testing & Diagnosis >> Circuit Test A - No Start

Circuit Test A - No Start

To prevent replacement of good components, be aware that the following non-EEC-IV related areas may be at fault: fuel quantity and quality, ignition system damage, cracks, moisture, etc., engine mechanical conditions such as valves, timing belt, etc. Also included are starter and battery circuit problems.

  1. Try to start engine. If engine does not crank, check vehicle starting and charging systems. If engine cranks, but does not start or else stalls after starting, go to next step.
  2. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect Throttle Position Sensor (TPS). Turn key on, leaving engine off. Measure voltage at TPS harness connector between voltage reference (VREF) and signal return. If reading is less than 4.0 volts or higher than 6.0 volts, go to CIRCUIT TEST C  . If reading is between 4.0 and 6.0 volts, reconnect TPS and go to next step.
  3. Disconnect any spark plug wire and connect spark tester between plug wire and engine ground. Crank engine and check for spark. If spark exists, connect spark plug wire and go to Step 13). If no spark, connect spark plug wire and go to next step.
  4. Remove high tension coil wire from distributor and install spark tester. Check for spark while cranking engine. If spark exists, connect coil wire and service or repair TFI ignition system. If there is no spark, connect coil wire and go to next step.
  5. Turn key off and wait 10 seconds. Install breakout box, leaving ECA disconnected. Set DVOM on 200 ohm scale and disconnect TFI. Measure resistance between test pin No. 16 and TFI harness connector ignition ground. If reading is more than 5 ohms, repair harness and repeat Quick Test. If reading is less than 5 ohms, go to next step.
  6. Connect TFI and ECA. Try to start vehicle. Move timing switch to "Distributor" position on breakout box. If vehicle starts, go to Step 10). If vehicle does not start, go to next step.
  7. Move breakout box timing switch to "Computed" position. Set DVOM on 20-volt scale and measure voltage between test pin No. 36 and chassis ground while cranking engine. If voltage is between 3.0 and 6.0 volts, EEC-IV alright and TFI should be diagnosed. If voltage is less than 3.0 volts or more than 6.0 volts, go to next step.
  8. Turn key off and wait 10 seconds. With breakout box installed, disconnect ECA and TFI. Set DVOM on 200,000 ohm scale and measure resistance between test pin No. 36 and test pins No. 16, 20, 26, 40, and 60 for short to ground. Measure resistance between test pin No. 36 and test pins No. 37 and 57 for short to power. Measure resistance between test pins No. 36 and 56 for short to PIP. If any reading is less than 10,000 ohms, repair short in harness and repeat Quick Test. If engine still does not start, go to next step. If all readings are 10,000 ohms or higher, go to next step.
  9. Turn key off and wait 10 seconds. With breakout box installed, connect ECA, but leave TFI disconnected. Set DVOM on 200 ohm scale. Measure resistance between test pin No. 36 and test pins No. 37 and 57 for short to power. Measure resistance between test pin No. 36 and test pins No. 40 and 60 for short to ground. If any reading is less than 5 ohms, replace ECA and repeat Quick Test. If all readings are 5 ohms or higher, connect TFI and go to next step.
  10. Set DVOM to 20-volt scale. Measure voltage between test pins No. 56 and 16, while cranking engine. If reading is between 3.0 and 6.0 volts, remove breakout box. Replace ECA and repeat Quick Test. If reading is less than 3.0 volts or higher than 6.0 volts, go to next step.
  11. Install breakout box, turn key off and wait 10 seconds. Set DVOM on 200 ohm scale. Disconnect TFI and ECA. Measure resistance between test pin No. 56 and TFI connector PIP circuit. If reading is 5 ohms or more, repair open PIP circuit and repeat Quick Test. If readings is less than 5 ohms, go to next step.
  12. Disconnected ECA and turn key OFF. Disconnect TFI connector and set DVOM on 200,000 ohm scale. Measure resistance between test pin No. 56 and test pins No. 16, 20, 26, 40, and 60 for short to ground. Measure resistance between test pin No. 56 and test pins No. 37 and 57 for short to power. Measure resistance between test pin No. 56 and test pin No. 36 for short to Spark Output (SPOUT). If any reading is less than 10,000 ohms, repair PIP circuit and repeat Quick Test. If all readings are higher than 10,000 ohms, perform TFI diagnosis.
  13. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector and inspect for damaged, loose, or corroded pins or wires. Repair wiring as necessary. Install breakout box and connect ECA. Make sure that box timing switch is in "Computed" position. Set DVOM on 20-volt scale and measure voltage between test pin No. 36 and chassis ground while cranking engine. If reading is between 3.0 and 6.0 volts on fuel injected engines, go to next step. If reading is between 3.0 and 6.0 volts on 2.3L OHC/FBC engine, check carburetor. If reading is less than 3.0 volts or higher than 6.0 volts on all engines, go to step 10) of this test.
    CAUTION: Next 2 steps apply to EFI and CFI models. 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.
  14. Disconnect all electrical connections at injectors. Connect pressure gauge to fuel diagnostic valve (if equipped) on fuel rail. Note initial pressure reading, then pressurize fuel system. (To pressurize system, turn key on for 1 second, turning key off, and then waiting 10 seconds. Repeat "ON, OFF, and WAIT" sequence 5 times. After final 10 second wait reconnect all injectors.) If pressure reading did not increased, go to next step. If pressure reading increased, go to CIRCUIT TEST Q  .
  15. With key off and fuel pressure gauge installed, push button on fuel pump inertia switch to reset it to ON. If switch will not reset to on, replace inertia switch and repeat step 14). If switch button was already on, go to CIRCUIT TEST V  . Observe pressure gauge as system is pressurized as in step 14). If pressure reading increases, repeat QUICK TEST. If pressure reading does not increase, go to CIRCUIT TEST V  .
Fig 1: TFI Module Circuits
G42673
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