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Old 08-20-2007, 12:34 PM   #1
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Blowing ignition modules

Just thought I'd put this puzzle up for you techies. I changed my 88YJ with the 4.2 6I over to a n HEI i bought a year ago. Ran great until recently. Started blowing ignition modules. So far 4. I changed to a different dist body, all the innerds of the dist, and still am blowing modules. Driving down the road at 45-50 mph, GONE! No symptoms-just quits and won't restart. Or it runs fine, I park it and two three days later, go to use it (NOT a DD) and it won't start. Making me crazy-and I don't need any help there. When it runs, runs great.

I and my mechanic buddy are stumped. He wants to go to a high output coil and the old points system. I want to know why it is blowing modules. Don't want to add something new 'til I know what is going on. Answers?

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Old 08-20-2007, 01:11 PM   #2
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i was gonna make a joke, but then saw ur name "grandpa jeepr" and decided against it

anyways, i have no idea what would blow modules like that, if it were me though id do what ur mechanic friend tells you to do,

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Old 08-20-2007, 02:37 PM   #3
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i was gonna make a joke, but then saw ur name "grandpa jeepr" and decided against it

anyways, i have no idea what would blow modules like that, if it were me though id do what ur mechanic friend tells you to do,
I don't mind jokes in good humor, it's when they get nasty I don't appreciate them. One of the reasons I like this site is that the people and board moderators know when to put restraints on teasing and "joking".
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Old 08-20-2007, 06:06 PM   #4
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I am not that familiar with the HEI system so I have a question I thought the HEI was a full ignition system some what like the MSD I installed on my 4.2 years ago. I removed the module from the system as the MSD now did that job. Is it possible the systems are fighting each other????
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Old 08-21-2007, 02:58 PM   #5
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I am not that familiar with the HEI system so I have a question I thought the HEI was a full ignition system some what like the MSD I installed on my 4.2 years ago. I removed the module from the system as the MSD now did that job. Is it possible the systems are fighting each other????
Good question. When I put in the HEI we used only the switched wire going to the original ignition module to fire the new unit. It ran for a year before it started acting up. I think the replacement modules were all too weak to work in the 30,000 volts unit. Put in a high end one just to see if it holds. Been debating switching to an MSD-6 and an old points system.

Any thoughts on that?
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Old 08-23-2007, 11:21 AM   #6
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Originally Posted by Hackle View Post
I am not that familiar with the HEI system so I have a question I thought the HEI was a full ignition system some what like the MSD I installed on my 4.2 years ago. I removed the module from the system as the MSD now did that job. Is it possible the systems are fighting each other????
This is also what I thought. I thought the system eliminated everything.
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Old 08-23-2007, 04:43 PM   #7
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i got a HEI ignition module, but i dont think i will hook it up. Have heard too many mixed complaints about the HEI and hybrid upgrades.
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Old 08-27-2007, 11:37 PM   #8
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Blew another expensive module over the weekend. Going to take my mechanic friends advise and switch to a high output coil and a points distributor. Haven't been able to go anywhere with it since Memorial Day weekend. Enough is enough! People are driving me crazy and I've got no release. Need the jeep to get out where I can shoot!
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Old 08-27-2007, 11:51 PM   #9
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if you havn't done the switch over already try running a redundent ground. and check the wiring for te module from the control and look at the waveform on a scope if you can. if its blowing the modules like that I would be suspectious about the ground and the wiring
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Old 08-28-2007, 10:42 AM   #10
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if you havn't done the switch over already try running a redundent ground. and check the wiring for te module from the control and look at the waveform on a scope if you can. if its blowing the modules like that I would be suspectious about the ground and the wiring
Wish it was that simple. I live in a small town in the mountains of Arizona where some of the houses come with custom one or two holers. Quite a few places have no running water and the closest community well is way down the road. I have tried driving the jeep the fifty miles in either direction to get to a shop with any advanced equipment only to breakdown just outside of town.

Some times I am driving and other times it just won't start again after I have driven it and it has been sitting for a couple of days. When it fails I have power at the primary wire to the HEI distributor unit, but no spark out to the plugs. Change the internal ignition module and it runs fine 'til next time. Towing is expensive on the paved roads. Don't even want to think what recovery would cost out in the boonies.

I will run new wiring from the switch to the coil and on to the points distributor. I'll keep y'all posted!
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Old 08-28-2007, 08:07 PM   #11
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Grandpa jeeper, when I installed the MC2100 it was a kit from a guy on ebay his instructions had me do this

Factory Electrical/Ignition
The factory ignition setup looks like this.
The violet and orange wires from the distributor must be cut, and the orange wire from the computer to the ignition module too. Trace this wire carefully, as there are at least two orange wires in that bundle and you don't want to cut the wrong one.
Notice the violet wire from the ignition module goes into the connector, but doesn't come out the other side. You must splice one here.
The module is under the washer reservoir, bolted to the fender.

Tricked Electrical/Ignition
This is what the ignition looks like after the modification. The solid-state ignition module is located under the washer reservoir. A length of wire must be added to extend the violet wire from the distributor to the ignition module. The distributor vacuum advance hose is moved from manifold vacuum to ported vacuum. You should add a tee here, since ported vacuum also operates the EGR valve. The stepper motor from the Carter BBD is unplugged.

Try this link if there are no pics

PS my carfb has the 47.5 jets
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Old 08-28-2007, 08:07 PM   #12
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Old 09-04-2007, 10:48 PM   #13
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Were you install the modules with the special grease they give you with the module? It purpose is to act as a heat transfer to the distributor body for cooling. Just an idea.

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