how to test a coil

[Boggin]

what is the most accurate way to test a coil? i think i may have mine blown on the mazda. thanks

 

[adsm08]

Grab the prop rod or some other part of the body. Then stick your tongue on the end of the coil wire and have someone crank the engine over. If you survive, you need a new coil. If you survive and have brain damage or need a pace maker now, you probably still need a new coil. If you die, you don't need a new coil, you won't be driving anymore.



Seriously though, if it's a distributor system, I like to take the dizzy end of the coil wire and jam a Philips head in it and hold the driver about 1/2 inch from the prop rod. Then have someone crank the engine. If you hear a sharp snap and see blue spark it's good. If you hear a weak crackling and see orange or red spark, coil time.

If you are not in direct contact with the body you shouldn't get zapped.

If it's a coil-pack system do the same thing, but pull the fuel pump relay first. And you gotta do it once for every coil.

 

[4.0B2]

can you get a hold of one off another mazda? me having the ex and b2 with an ex's drivetrain, i just swap parts around

 

[Boggin]

Grab the prop rod or some other part of the body. Then stick your tongue on the end of the coil wire and have someone crank the engine over. If you survive, you need a new coil. If you survive and have brain damage or need a pace maker now, you probably still need a new coil. If you die, you don't need a new coil, you won't be driving anymore.



Seriously though, if it's a distributor system, I like to take the dizzy end of the coil wire and jam a Philips head in it and hold the driver about 1/2 inch from the prop rod. Then have someone crank the engine. If you hear a sharp snap and see blue spark it's good. If you hear a weak crackling and see orange or red spark, coil time.

If you are not in direct contact with the body you shouldn't get zapped.

If it's a coil-pack system do the same thing, but pull the fuel pump relay first. And you gotta do it once for every coil.

i knew of that way but just wondered if there was a better way, like even some way to do it with a test light or volt meter?
thanks though!

 

[adsm08]

You can always ohm the primary windings, but that test is ineffective at best since a new coil and a functional but weak coil will usually ohm the same or close, and I've done resistance tests that showed good on non-functional coils.

Using a test light or voltmeter to test it is not a great method for a few reasons. "Slow" firing of the coil is still thousands of times a second. That makes it hard to accurately gauge how well it fires since it is running at thousands of hertz while your eyes can process about 60hz. Also, these coils produce up to 40 Kv and a few hundred amps. that will just fry your meter and probably your test light too.

A load test with the screwdriver or an actual spark tester (which functions much the same way) is the best and most accurate method.

 

[lil_Blue_Ford]

So that's how the spark plug tester screwdriver I picked up is supposed to work...

Wasn't sure how it was supposed to be used, I got it without any instructions, just a flat head screwdriver with a spring in the handle and it's labeled "Craftsman Spark Plug Tester." I threw it in my toolbox and it's sat there for the past 4 years or so...

 

[AgPete139]

Boggin, when did you get the Gen3?

 

[Boggin]

Boggin, when did you get the Gen3?

this summer, few months ago