[s-cars] coil diagnosing

[chris chambers]

I will assume you already checked the coil wires for breaks, this is a
known problem. Others have "fixed" their coils by simply wrapping the
break in electrical tape.

I have a bad coil and while searching fouond the following test
procedure.


"Here is hopefully a quick and inexpensive test for your suspect coil.
Go buy an adjustable spark tester. Try to get one with the thumb screw
that you can manually adjust the gap with. Cost is usually around $9.00

Lay the coil packs on the valve cover.
Disconnect the coils that aren't being tested.
Use a short plug wire and connect one end to the coil to be tested and
the other end to the spark tester. Adjust the spark tester to, I'll say
start with the 0.020 gap size. This will probably equate to about 1/4
inch on the tester. Get someone to crank the engine while observing
spark. There should be a nice blue, crisp sounding spark. Proceed to
test all coils to get a baseline as to the spark quality. Then proceed
to adjust the spark tester to a bigger gap while observing the quality
of the spark After some time and patience you will notice that the
spark will turn yellow and will not have that crisp sound as the
others. Obviously this will be the bad coil. On a side note you may
also want to disconnect the injectors so as not to load the converter
up with raw petrol.

I use this test all the time it never fails. The reason the tester is
so effective is because you're dynamically testing the coil. As you
know when the spark plug is in the cylinder ,the spark "has to under
extreme pressure try and ionize the gap.This puts extreme loads on the
igniton coil secondary circuit when your are under load/boost. This
tester will simulate this condition every time. "


Searching the net I found a pic of an adjustable spark tester here:
http://www.drivewerks.com/catalog/images/tools2003/THE-404.jpg 

And have since found the tester available at Auto zone.



HTH
Chris

AUDI - Accelerates Under Demonic Influence.

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