Current Ramping – Analyzing Amperage Results

Part 2: Analyzing Amperage Results When Testing Ignition Coils with a Low Amp ProbeCheck out Part 2 of Barry Gersten’s Current Ramping series. This time, he covers how to analyze amperage results when testing ignition coils with a low amp probe.

Measurement A

Evaluate the Rise Time or Ramp-Up Time (time it takes to go from zero amps to peak amperage) – Compared to a normal coil – is the Rise Time the same, more time or less time?

The Same – Continue testing.
More Time – High resistance in, or to the coil is indicated. Usually, a weak spark results. Use an Ohm Meter to determine if the coil has abnormally high resistance. Also, check connections at the coil and to the coil for resistance. Common complaints are reduced power, reduced gas mileage, long cranking time. Repair as necessary.
Less Time – Current will show a faster rise time when there is less resistance in the coil. Usually, faster rise time implies a shorted coil. Common complaints are intermittent ignition miss or miss on acceleration. Usually, coil replacement is necessary.

Measurement B

Evaluate Saturation Time – The period of time that the coil is saturated with current flow influences the energy available for the secondary ignition spark. Compared to a normal coil is saturation of the same time duration?

The Same – Continue testing.
More Time/Less Time – The time duration for coil saturation is determined by the ignition module. Any abnormalities in duration of saturation time are usually because of a fault in the module. In some cases the crank sensor or distributor trigger pick-up may be involved.

Measurement C

Evaluate the Peak Current – Compared to a normal coil – is the Peak Current the same amperage, more amperage or less amperage?

The Same – Continue testing.

More Amperage – An Internally Shorted or Low Resistance Coil will allow excessive current to flow.

NOTE: A Current Limited Module will allow only the normal amount of current. However, a shorted coil is revealed by the faster rise time of the current. If the circuit is NOT protected by a Current Limiter it is necessary to observe how much more than normal is the amperage.

• If the amperage is at or less than 50% above normal – replace the ignition coil.
• If the amperage is more than 50% above normal – replace the coil and the module.

Less Amperage – The coil may have high internal resistance, connections may be poor or have high resistance, check those items with an Ohm Meter. If they check good the module may not be allowing enough current to the coil.