Ignition question, No longer thinking ignition.... Options

[1bwilson]

So I lend my jeep to a friend for a few weeks and go to drive the celica and find it running rough. After a bit of investigation Ive found the im getting a very small amount of spark from wire #4. So I did the usual swap plugs, new wires, new cap, new rotor...... Nothing, still a weak spark. So weak infact that its not even igniting fuel. Im not excited about the possibility of a pinched wire somewhere in the harness and im even less excited about the idea that I may have to hunt it down. So before I start pulling things apart let me go over what I know it isnt and hopefully someone will see light where I cannot.

out of the 3 mains (fuel,spark and air) Ive already figured out its the spark.

Its only happening on the #4 wire

Its not the plug, wire, distro cap, rotor as I have replaced them all.

I AM getting spark but its very weak and at times not there at all.

The old cap had burn/spark marks on the pins accept for the #4 one where it looked almost new.

I cant see any pinched wires but that doesnt mean something has worked itself loose some where out of view.

An option I have is running a MSD 6a ignition (if that would bypass my problem), Ive had one sitting on a shelf for almost 5 years and I have yet to install it. The only problem is I dont know how/which diagram to use for the install.

/discuss

This post has been edited by 1bwilson: Aug 29, 2008 - 7:04 PM

[Hanyo]

how would a compression test related to a bad spark plug in a cylinder? (trying to get the fundamentals down)

[1bwilson]

how would a compression test related to a bad spark plug in a cylinder? (trying to get the fundamentals down)

Because I could have screwed the pooch here and assumed that it was the weak spark and not thought of the other possibilities before I started replacing things. Yes the spark was VERy weak and replacing the ignition items did improve it somewhat, but that may not have been the issue at all just happened to be the first assumption.

Like I said the way I concluded it was I pulled the wire and nothing changed in the idle, assuming it was a ignition issue and not a compression issue.

I used the word assume quite a few time to get the point across that assuming is a bad idea. Always check all your outs before spending a bunch of cash fixing what you ASSUME is wrong.

Just got him from work, doing a compression test now. Ill post the results in a few.