Carl Heideman
Carl Heideman
10/7/08 10:04 a.m.

If there is any ignition component that gets an unfairly bad rap, it’s the coil. Coils are very quickly blamed for ignition problems, yet almost universally they are not at fault. Coil manufacturers must love this, however, as it sells a lot of coils.

We discussed the theory behind an ignition system in our last issue, and now it’s time to troubleshoot common problems. Ignition problems generally fall into two categories: Things that cause the car to not run at all, and things that make the car run poorly.

A 12-volt test light is your best friend when diagnosing ignition problems that keep a car from running. If your car still has points, a tach/dwell meter and a timing light—preferably a dial-back type—are pretty important cousins to your test light when it comes to figuring out why it’s running poorly.

A little common sense will also go a long way. Always keep your fingers and other appendages clear of a spinning cooling fan—if it’s thermostatically controlled, remember that it can turn on when the engine is off—and don’t forget that a coil can pack a wallop.

Let’s start with a diagnosis plan that should uncover most ignition problems found.

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distributorguy New Reader
7/11/18 10:53 a.m.

You should also test the spark plug wires.  0- 5000 Ohms is a good range for the plug wires to operate within.  Anything above 5000 Ohms per wire will stress the coil and force other failures in the HT (10kV+)system.  They can even lead to misfires which can destroy an electronic ignition or a condenser in the LT (12V) triggering system.  

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