no spark issue

wrencher

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Feb 9, 2007
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Make
olds
Model
calais
Year
1985
Miles
150k
Engine
2.5
Hello....
Does anyone know how to test the coil?

thanks
wrencher
 

grcauto

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It's not likely that all three coils failed ar the same time. You have a crank sensor, cam sensor, Ignition Module, ECM and coil pack all of which are needed for spark control.
Without a scope to properly check signal quality you will likely be throwing parts at it. I would suggest trying a new ignition module as they are the most common problem.
 

wrencher

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Thanks for your reply, but this is just a single coil for a 2.5 4cyl....here is a generic pic of what one looks like I grabbed off the net....
the module was replaced and is only about a year old, but I tested it anyway and it is good. I just want to test the coil before
I go any further.

thanks
wrencher
 

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billr

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That is off an engine with CNP (Coil Near Plug, as opposed to COP)? The easiest way is to swap it with a coil from another cylinder on the engine; see if the spark problem follows the coil, or stays with the one cylinder.
 

Mobile Dan

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1641580005279.pngOne of these will test A. Is it working? and B. how "strong" is the spark? Turning the red knob increases the gap that the spark must jump...a healthy coil (and related components) will be able to jump a gap about 3/4" wide.
 

Mobile Dan

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1641580690716.pngSpecial pliers like this can perform the same test by using them to hold a spark plug wire (or coil wire) close (about 1/8th") to a metal (grounded) part of the engine and look for spark. Then slowly move wire farther away from engine to see how far the spark will jump. Disclaimer: this is perfectly safe if you do it right (easy), but thousands of (low amperage) volts can really sting if you do it wrong.
 

Mobile Dan

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1641581966174.pngIf you have a good knowledge of how electricity works (and I guess you don't) you could get the job done with a jumper cable with well-insulated handles. This could be pretty simple, actually. Clamp one end of a cable to engine metal, hold other end 1/8" from coil "post" and crank engine (gonna need a helper?) and look for spark.
 

Mobile Dan

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1641583403225.pngThis schematic is JUST AN EXAMPLE if you are asking about tests you can do to see if the coil has failed internally or is not getting the power it needs to operate. There are voltage and ohms tests that can be done.
1641602967080.png
1641603215109.png
 

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Last edited:

billr

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Oops, I sure missed that this is an '85; a single-coil system. I was reading the OP's description to mean that only one coil in a multi-coil system was suspect...
 

wrencher

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Hey Guys...
thanks for all your replies...yea it is a single coil system on a 4cly 2.5 motor. I'm just basically looking for how to test, (with an Ω meter) the primary
and secondary of this coil before I buy a new one. i think it is bad, but I would just like to test it first. Or maybe a flow chart might help? I don't know.
If someone has a pic of one or a link that might help also..

thanks
wrencher
 

wrencher

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thanks for the chart Dan....and yes, YOU ROCK!
test 1 I couldn't really tell what reading I was getting, maybe infinity.
test 2 was 1.9
test 3 was 8.4
I will probably just try a coil tomm. and see what happens.

thanks
wrencher
 
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