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coil and spark problem


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jnrwood
New User

Oct 1, 2011, 3:34 PM

Post #1 of 7 (2030 views)
coil and spark problem Sign In

Hi, we have a 1997 gmc sierra p/u truck.It has a 350 ci engine.
The problems with this truck started on wet and rainy days. It would be hard
to start and then run rough until it dried out. We have replaced the coil,
wires, dist cap and rotor. I suspect we got a bad coil because, when you crank it, a spark is visible
coming from the base of the top terminal (high voltage) on the coil, going to the square metal plates that make up the
body of the coil. the spark appears to be coming right thru the plastic at the base of the high voltage terminal,
the one that leads to the distributor. I know thats not right. When spark is checked at the plugs,
its there, but appears weak- sort of an orange color.
The question is, could there be something that is causing these coils to go bad, within the distributor,
for instance, or did we just get a bad coil? thanks, jon


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 1, 2011, 4:00 PM

Post #2 of 7 (2001 views)
Re: coil and spark problem Sign In

The coil is likely cracked but make sure you don't have excessive resistance in the secondary wiring.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



jnrwood
New User

Oct 1, 2011, 5:06 PM

Post #3 of 7 (1988 views)
Re: coil and spark problem Sign In


In Reply To
The coil is likely cracked but make sure you don't have excessive resistance in the secondary wiring.


Ok, but do you mean the secondary wiring within the coil? or the hv wire to the distributor.?
if the resistance is off within the coil, it still needs replacing, right? thanks for your help


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 1, 2011, 5:09 PM

Post #4 of 7 (1983 views)
Re: coil and spark problem Sign In

No, those things would be the primary side of the circuit. The secondary is the coil wire, ignition wires and plugs. I know you said you changed them but heavy corrosion at any contact will increase resistance.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



jnrwood
New User

Oct 1, 2011, 5:20 PM

Post #5 of 7 (1979 views)
Re: coil and spark problem Sign In

10-4, will check it out tomorrow


jnrwood
New User

Oct 2, 2011, 3:17 PM

Post #6 of 7 (1959 views)
Re: coil and spark problem Sign In

Ok, you were right. Checked the resistance on high voltage wire- coil to distributor
and it had "infinite" ohms. Was new one year ago- bosch premium wire. Found the
old one (wire) up at the shop, and the thing started right up, and runs good, with the same coil.
how does that happen? the wire looks fine, but... anyway, thanks hammer time,
we're cruisin now!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 2, 2011, 3:31 PM

Post #7 of 7 (1955 views)
Re: coil and spark problem Sign In

Just normal deterioration. The better the quality wires, the longer they will last.
Glad to he you got it resolved.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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