No Start Test

For additional diagnosis procedure, refer to the Throttle Body Fuel Injection Section for 4-150 engines or the Multi-Point Fuel Injection Section for 6-243 engines.

Fig. 4 Ignition Control Module (ICM) connectors:

ENGINE WILL NOT START (WEAK OR NO SPARK AT SPARK PLUGS)

1. Check for damaged or damaged ignition coil, rotor, distributor cap, ignition wires and spark plugs and repair or replace as necessary.
2. Check for loose wire connections at ignition coil.
3. Check for loose connections at ECU and ICM.
4. Check for loose or corroded ECU or ICM ground wire connections.
5. Check condition of battery and recharge or replace as necessary.
6. Check voltage between terminals A and B of ICM connector terminal 1, Fig. 4. With ignition switch in the Start position, voltmeter should indicate a minimum of 9.5 volts.
a. If a minimum of 9.5 volts is indicated, proceed to step 7.
b. If voltage is less than 9.5 volts, check continuity of ICM and ECM ground wires and repair as necessary. After repairing, recheck and proceed to step 7.
7. Check condition of ignition coil.
a. Check ignition coil for exterior damage such as cracks and or severe dents and replace as necessary.
b. Connect a suitable ohmmeter between ignition coil positive and negative terminals to check primary resistance. Ohmmeter should indicate .4 to .8 ohms, if not replace coil.
c. Connect ohmmeter between positive or negative terminal and coil high voltage terminal to check secondary resistance. Ohmmeter should indicate 2500 to 4000 ohms, if not replace coil.
d. If ignition coil is satisfactory, proceed to step 8.
8. Using Tester MS-1700 or equivalent, check ICM and ECU. Refer to instructions supplied with tester for test procedure. Replace ICM or ECU if defective.




SECONDARY CIRCUIT TEST

1. Disconnect ignition coil wire from distributor cap.
2. Using insulated pliers, hold ignition coil wire approximately1/2 inch from a good engine ground.
3. Crank engine and check for spark at coil wire.
a. If spark is present at coil wire, proceed to step 4.
b. If spark is not present, refer to "Engine Will Not Start (No spark or Weak Spark at Spark Plugs)" and "Fuel Injection Section" for further diagnosis.
4. Disconnect wire from spark plug and hold approximately 1/2 inch from a good engine ground with insulated pliers. Crank engine and check for spark at spark plug wire.
a. If spark occurs, refer to "Fuel Injection Section" for further diagnosis.
b. If spark does not occur, check for defective rotor, distributor cap or spark plug wires.