How can you test Coil Packs?

[Oily Mick]

Is there a way to test them out of the engine, with a multimeter, or meggar for instance?

 

 

[Jorgen]

There is a procedure that involves measuring resistance, but i am not really sure how. Its been covered before so suggest you search the archives. Or somebody with more knowledge will come along in a minute a help.

[Peter T]

Yes there is, but........... most coil packs fail when in service due to excessive heat and energy that is placed on them in service.

Simply testing them in situe does not replicate the full electrical loads and heat placed on them to fail.

Really the only way to test them is to observe the resistance throughout the entire rev range and load conditions which is nigh on impossible to do.

Best to subsitute with another known good unit to determine if yours has a fault and cheaper and quicker too.

[Pooh_R]

I quite agree. Off the car testing is of very limited benefit due to the nature of most failures. That said, if either of the windings are open circuit, you know you have a faulty coil. Primary winding should be about 1 Ohm, and secondary several kOhms.

 

The only was to test a coil without replacement is to measure the input coil driver signal to ensure it is correct, and measure the output voltage and see whether it is ok. Both of these need a scope to do properly.

 

Pooh

[Bob_Rich]

The coil pack has to produce a voltage around 30kV peak for a few hundred of microseconds to produce the spark. The actual voltage is determined by the plug breakdown voltage which is itself determined by the loading on the engine ( more throttle--- denser charge--so more volts to get breakdown across the plug) Coils usually fail either with a gross breakdown of the insulation or with a short between a few of the turns. With the shorted turns sometimes a just adequate spark spark can be obtained at light load. Generally resistance checks do not vary much with shorted turns or other voltage breakdowns and a megger is a relatively "low" high voltage (1000V) and is DC so would not simulate the correct short impulse voltage working of the coil.

 

To fulyl test the coil pack you need to pulse the coil with a similar signal to that produced by the ECU.

 

either a temporary swop from a mate with a working unit of the type you have, or access to proper pulse voltage measuring equipment is the only sure test.

 

Hope this helps

 

regards

 

Bob

[Oily Mick]

thanks chaps. will have to swop with someone else, when they're not looking!

😬