Ignition, Fault Diagnosis – 1

~ Engine Won’t Start or Fire ~

There are three main symptoms indicating faults. Either the engine will not start or fire, or the engine is difficult to start and missfire, or the engine shutdown suddenly and start again after few minutes resting.

If it is a regular missfire, ie the engine is only running on two or three cylinders the fault is almost sure to be in the secondary, or high tension circuit.

If the misfiring is intermittent, the fault could be either the high or low tension circuit.

If the car stops suddenly or will not start at all, it is likely that the fault is in the low tension circuit.

Loss of power and overheating, apart from faulty carburation settings, are normally due to faults in the distributor or incorrect ignition timing.

# Engine Fails To Start

Reasons :

Lack fuel in tank
> Fill up fuel

Bad battery terminal or ground
> Tighten up

Bad battery power
> Charge battery

Wet or damp spark plugs lead and distributor ( if applicable )
> Dry up the cap with rag, wipe the lead. Replace cap if necessary

No current reaching spark plug, on old model. On present model, ignition coil placed right above the spark plug.
> Disconnecting each plug lead ( LT ) in turn at the spark plug end, holding the end of the cable about 3/16 in ( 5 mm ) away from the cylinder block. Spin the engine on the starter motor. Good spark shown great blue spark.

Note : make sure the car clear from any body contact. It’s high tension !

If the LT resulting no spark at all plugs
> Take of the HT lead from center of the distributor cap and hold it to the block as before, make sure blue spark appear.
A rapid succession of blue sparks between the end of the lead and the block indicate that the coil is in order and that the distributor cap is cracked, the rotor arm faulty, or the carbon brush in the top of the distributor cap is not making good contact with the spring on the rotor arm.
Possibly, the points are in bad condition. Clean and reset the contact points.

Brake off ignition switch
> Use a 12v voltmeter or a 12v bulb and two lengths of wire. With the ignition switched on and the points open, test between the low tension supply lead on the switch side of ignition coil and earth. No reading indicates a break in the supply from the ignition switch.
Check the connections at the switch to see if any are loose. Refit them and the engine should run.
A reading shows faulty coil or condenser, or broken lead between the coil and the distributor.

For testing the fault of condenser, lead, and coil. Please do read at The Condenserfault, and The Lead and Coil fault.

For these test, it is sufficient to separate the points with a piece of dry paper while testing with the points open.

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