Refer to figure 5-17 and to the appropriate vehicle wiring diagram.

When the engine will not start or when hard starting or missing indicates a faulty ignition system, proceed as follows:

1. Disengage spark plug cables. Check condition of plugs and cables. Clean or replace as necessary.

2. Insert an extension adapter into spark plug nipple and establish a 3/16 in. gap between adapter and cylinder head. Turn on ignition and engine stop switches. Crank engine. Check to see if a spark is obtained across the gap. If a spark is obtained, the problem is not in the electronic system or coil. Check carburetion, choke, spark plugs, and advance mechanism.

3. If no spark is obtained, check battery voltage and battery connection condition. Turn on ignition and engine stop switches and with a voltmeter across the battery and current flowing, voltage should be 11.5 or above. If voltage is low, battery needs charging.

4. Remove the timer case cover and position ignition module to one side. Check the air gap between both trigger lobes and the sensor. Air gap must be 0.004 to 0.006 in. If this gap cannot be held on both rotor lobes, timer mechanism shaft and/or trigger rotor have excessive runout and should be replaced or straightened. Check to make sure tnat control module ground black lead is securely fastened to timer plate and that wires are in good condition.


Whenever sensor air gap is adjusted, the ignition advanced timing should be checked and adjusted if necessary. See "Adjusting Advanced Timing with Strobe Timing Light." If spark is still not evident, continue with the following voltmeter checks.

Position trigger rotor so that the center of the sensor is between two lobes.

5. Connect voltmeter between ignition positive coil terminal (white wires) and engine ground. With ignition and engine stop switches on, the voltmeter reading should equal battery voltage within 0.5 volt. If not, trouble lies in circuit between battery and ignition coil. Check the connections at or in circuit breakers and ignition switches.

6. Disconnect blue wire from coil negative terminal. Connect voltmeter between coil negative terminal and ground. With ignition and engine stop switches on, the voltmeter reading should equal battery voltage. If not, ignition coil primary is defective. Replace coil. Retest for spark after corrections are made.

7. Reconnect blue wire to coil negative terminal. Connect voltmeter between coil negative terminal and ground. Reading should be 1 to 2 volts. Place the blade of a screwdriver against the face of the sensor. If the voltmeter reading switches up to 11.5 to 13 volts, proceed to step 8. If the voltmeter does not switch up and down or does not read 1 to 2 volts, the ignition module is faulty and must be replaced.

8. Re-establish the 3/16 in. gap between spark plug cable and ground. Check for a spark discharge each time the screwdriver blade is placed against the face of the sensor. If sparks are not observed, the coil secondary is faulty and the coil must be replaced.

CAUTION — Coil wires must be connected correctly. Both white wires must be connected to the same coil primary terminal or ignition control module will be permanently damaged.


Ignition timer sensor air gap should be checked initially al 500 miles and thereafter every 2500 miles. Remove spark plugs to permit engine to turn easily and rotate flywheels so that the wide lobe on the trigger rotor (1) is centered in the sensor (2). Check the gap between the rotor and sensoi using a narrow feeler gage. If gap is not correct, looser screws (3) and move sensor as required. Repeat for narrow lobe setting so that gap for both lobes in between 0.004 and 0.006 in. Tighten screws (3) to 5 to 7 in-lbs torque.

Figure 5-18. Trigger Rotor Position for Ignition Timing

Flywheel Markings





1. Trigger rotor

2. Sensor

3. Sensor screws (2)

4. Timer plate

5. Timer plate screw (2)

6. Plate adjusting notch

8. Fully Retarded (3° B.T.C.) position of piston top center mark on flywheel

9. Timing inspection hole

10. Ignition module

11. Ignition module ground screw

Figure 5-19. Ignition Timer and Flywheel Timing Marks


Ignition timing should be checked initially at 500 miles and thereafter every 2500 miles.

Before checking timing, check sensor air gap as described above.

Use a strobe flash timing light (timing gun) to view advanced timing (7) on flywheel through accessory plastic view plug, Part No. 96295-65, screwed into timing inspection hole (9). Make sure view plug does not touch flywheels. Timing light leads should be connected to the front spark plug, ground and battery positive terminal. Start engine and set engine speed at 2000 rpm. Light will flash each time spark occurs (see figure 5-20). Loosen timer plate screws (5) just enough so that plate (4) can be shifted using a screwdriver in notch (6) as light aimed into inspection hole (9) stops timing mark (7) in center of hole. Timing will retard 30° automatically when engine is at idle speed or is stopped.

Rear cylinder advance timing mark is a single large drilled dot which should appear on or near the front cylinder advance timing mark while viewing with timing light. See figure 5-20.



This procedure will result in approximate timing and engine can be operated in an emergency for a short period of time. Advanced timing should be checked and set under running conditions as soon as possible using a strobe timing light as described in preceding section.

Figure 5-20. Checking Timing with a Strobe Light

Whenever ignition components have been disassembled, such as during engine disassembly and reassembly, or if a strobe timing light is not available, approximate timing can be obtained by using the following procedure.

Remove screw plug from timing inspection hole (9) in left side of crankcase. Then remove front push rod cover so that opening and closing of valve can be observed.

Turn engine in direction in which it runs until front piston is on compression stroke (just after front intake valve closes), and continue turning engine very slowly (less than 1/2 revolution) until piston top dead center timing mark (8) on flywheel is aligned in the inspection hole as shown.

With timer rotor fully retarded, the leading edge of the narrow rotor lobe should be aligned with the center of the sensor body as shown in figure 5-18. At this point the retarded front cylinder ignition spark occurs. A circuit tester, such as a 12-volt light bulb (No. 57) can be used to determine the exact point of ignition firing as follows: Disconnect the blue wire from the ignition coil primary terminal and connect test light to this terminal and to end of removed blue wire.

Loosen timer plate screws (5) just enough to shift timer plate (4) using a screwdriver in notch (6), so light goes on or off when piston top dead center timing mark is aligned in inspection hole (9) as shown in figure 5-19. Tighten screws (5) to 12 to 16 in.-lbs. torque.

When reinstalling the control moauie ana timer compartment cover, make sure that wires are not pinched between the control module and internal components.

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