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Home >> Jeep >> 1986 >> Pickup J20 >> Repair and Diagnosis >> Engine Performance >> Ignition System >> Ignition System - Solid State >> Testing >> Coil Primary Circuit Check

Coil Primary Circuit Check

  1. Connect voltmeter positive lead to coil positive terminal and negative lead to ground. With ignition on, reading should be 5.5-6.5 volts. If voltage is high, proceed to step 3). If voltage is low, remove condenser lead. If voltage is now correct, replace condenser. If voltage remains low, proceed to step 6).
  2. If voltage was 5.5-6.5 volts in step 1), turn ignition switch to "START" position. Voltage should be the same as battery cranking voltage. Check wire connected to starter solenoid "I" terminal for shorts or opens. If wire is okay, check for defective starter solenoid and replace if necessary.
  3. With ignition on, disconnect wire connected to starter solenoid "I" terminal and measure voltage at coil positive terminal. If voltage drops to 5.5-6.5 volts, replace starter solenoid. If voltage does not drop, resistance wire is defective.
  4. Replace resistance wire and repeat step 2). If voltage drops to 5.5-6.5 volts, turn ignition off and connect ohmmeter lead to coil negative terminal. Connect the other lead to terminal "D4" of the 4-wire harness connector. If continuity exists, replace the control unit.
  5. With ignition off, connect ohmmeter leads between coil positive terminal and dash connector "FW". If resistance is not 1.3-1.4 ohms, replace resistance wire. If ohmmeter reading is correct connect ohmmeter leads between dash connector "FW" and ignition switch terminal "L1".
  6. If resistance is less than 0.1 ohm, repair feed wire or replace ignition switch. If resistance is more than 0.1 ohm, check for opens in wire or for poor connections at connectors. Repair or replace as necessary.
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