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Discussion Starter · #1 ·
A friend of mine left his jeep at my place because it wouldn't start after a day of wheelin. Ran perfect on Saturday, Went to start it Sunday and was a no spark. It's an 89 with a 4.2 and a Howell injection on it. Also has a newer looking distributor on it (the Howell kit is a new thing to me). It's getting fuel, pulled the air cleaner and watched both ports spray fuel. No spark though. The only thing we did between Saturday and Sunday was that he had a guy weld a piece in his front bumper, battery still hooked up. Did something fry? Where do I start?


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Yes, the Howell system has an OBDI diagnostic port, but the ignition system is not computer controlled in the Howell setup, so this port will not provide any useful info on the spark problem.

It is most likely that with the battery still hooked up you fried something. The culprits for no spark would most likely be the ICM and the ignition coil. Those are the two components that could easily fry from the high amps put out by a welder. Off-hand I don't know of any ways to test these components to see if they are good.

Because you have this spark problem, you'll also want to check all of the fuses to make sure they didn't blow. Always disconnect the negative cable from the battery whenever welding on the frame or body.
 

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Discussion Starter · #4 ·
Roger that on disconnecting the battery. All fuses are good, replaced the coil. Both connections are hot in run position? Seems weird to me. Was like that on the old one too. ICM is the little block in the firewall below the battery? That's next. Thanks.
 

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i had the same problem with my 89 with a howell. one time it was a bad icm. then another was a bad coil. change out the icm. make sure that your coil has a resistor too. looks like it doesn't have one right now which will keep blowing it.
 

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Discussion Starter · #6 ·
A resistor in the coil or before it? It's got two wires coming off one side and one off the other. Haven't chased them yet, both are hot.
 

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The 1987-1990 YJ 4.2L has has a resistance wire built into the harness. This wire performs the same function as a ballast resistor.



The yellow highlighted wire (with the zig-zag squiggle) is the resistance wire. It is buried in the main engine bay harness and should look different from the other wires, and may say "Do Not Cut" on the insulation (as it did on mine). As it isn't part of the computer harness, it should not have been touched when the Howell upgrade was done and should still be in place. As long as that wire is in place, there is no need for any concern.

That said, an external (non-wire) ballast resistor would not have saved the coil and ICM from the current the welder put through the Jeep.
 

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Discussion Starter · #8 ·
Thanks NonRubicon. I will check again tomorrow. There is a yellow wire going to the coil and I will see what it is. Is it safe to assume that it is the resistance wire that you are talking about being that it ran fine the days before it quit?
 

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The resistance wire isn't like a fusible link that will blow with too much current (at least it isn't designed to behave as such, although with enough overcurrent any wire can blow). It should still be there from the original harness as it wasn't in the computer harness and anything not in the computer harness should have been retained. You aren't going to find the resistance wire unless you pull the main harness from the firewall and upon it up.

I'd focus on getting the new ICM installed and see what you get.
 

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Good to hear. Be sure to disconnect the battery next time before welding anything on the Jeep!

:drinks:
 
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