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PottsyCJ5 06-23-2018 08:59 AM

Prestolite ICM - Not Required for this setup?? 75í CJ5 304 V8
Hey Fellas - can someone please help me understand why it seems my setup does NOT require the prestolite ICM that WAS still hooked up in my CJ? In another thread I posted trying to figure out what this ďgray ooze leaking black boxĒ was, I think someone on here mentioned I didnít need an ICM with how the PO setup my 304, but Iím hoping someone can explain why in detail so I can rest easy now that I unplugged it.

Hereís the skinny...the PO definitely changed some things out on the setup 75í, but his dad who did the work died and I have no history on the vehicle. I believe from stuff posted by members here, the distributor I have is not the original style for this year, but I donít fully understand what is different between this dizzy and whatever the stock dizzy was.

The prestolite ICM pictures has been leaking/oozing tacky gray plodding since I bought the Jeep (I canít believe there is still anything left to ooze at this point), and I was about to just order a new one to have on hand for fear it was gonna die soon BUT (at the advice of Matt) I just disconnected to see if the Jeep ran without it, and it did. It starts fine without it (Jeep was already warm if that somehow matters) and it seems to run fine going down the road with it disconnected as well. My understanding is that if I do need the ICM the jeep would either not start or not run without it?

So my questions are:
1) What is different in my setup from the stock configuration that makes the ICM no longer necessary?
2) since the Jeep starts and runs with the ICM unplugged, that indicates I definitely do NOT need it correct?
3) could disconnecting the ICM in this configuration cause any issues with timing, performance, or anything else I might not realize immediately? I want to be sure Iím safe with just leaving it disconnected.
4) finally, is this setup a ďbetterĒ setup than the stock configuration? I have read these ICMs fail often so it seems like maybe itís a good thing I donít seem to need it, but need help understanding if that logic is correct.

Essentially I want to confirm the ICM is really not needed, and that I am not going to do any damage to the Jeep running it with the ICM unplugged, or that Iím not missing out on anything but not running one. This is an area where my knowledge is pretty limited at this point, so I really appreciate any guidance you can provide. I really want to understand why itís no longer needed (if it really isnít) so I can stop worrying about it. Like I said, I was about to order a backup because I had a feeling it was gonna go soon based on the amount of oozing, but it seems the PO adjust left it wired up but itís not doing anything (except drawing and current and cooking itself).

Thanks for the help as always. If better photos are needed let me know. In the second pic, I have the ICM unplugged.

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Matt1981CJ7 06-23-2018 12:23 PM

The engine would not run with the old ICM unplugged if it was needed. So you are doing no harm by unplugging it.

I'm not sure what type distributor/ignition system you have, but the easy way to figure where the new ICM is located is to follow the wires from the distributor. They will terminate at the ICM that your current setup is using.


PottsyCJ5 06-23-2018 01:12 PM

Prestolite ICM - Not Required for this setup?? 75í CJ5 304 V8
Thanks for replying Matt. Are you saying I must have another ICM somewhere? The only other thing that looks like an ICM is the smaller black box next to the prestolite, but it was explained to me in other threads that that is a Motorola voltage regulator for my alternator. Iím almost positive there is not another ICM onboard.

Iíll trace the wires from the distributor and look again.

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John Strenk 06-23-2018 01:52 PM

1 Attachment(s)
It could be an early points distributor. No ICM needed for that.

Can you put a GM Chevy points distributor on an AMC V8?

The distributor on there now has that little "door" on it where you would adjust the points with an allen wrench.
I remember doing that on my '63 Chevy V8

You can see it peeking out right were the two hoses come together.

Matt1981CJ7 06-23-2018 02:12 PM

I think John may be on to it. :thumbsup:

It seems odd they'd swap to a points distributor, but you never know with POs I guess.

It's safe to say your old ICM is no longer in play, so unplugging it does no harm. You could remove it entirely, along with the wiring harness that plugs into it, if you wanted to tidy things up a bit.


PottsyCJ5 06-24-2018 03:35 PM

Thanks Matt and John as always. For good measure, I did trace the wires off the dizzy, and aside from spark plug wires, the only wires coming from the distributor go directly to the coil. One that seems like a ground perhaps, and the other being the main coil wire. Good to know I donít need to worry about this thing oozing anymore; Iíve been worried it was gonna leave me stranded.

That said, I donít know much about distributors. Is a Points setup considered reliable? Iím not ready to start thinking about any kind of HEI conversion at this point, but do want to know if I can expect this to be a reliable setup. Iím running this thing a lot and want to be able to count on it. If there is a better alternative that is pretty straight forward to swap to, Iíll consider it.

I will say, when I adjusted the timing, it was VERY difficult to get the distributor to turn in order to get it back to 5 degrees BTDC. It was set to 10 by PO, and I wanted it set to factory spec. It took a pair of channel locks to get it to turn. Because of that, I have been thinking it might be a good idea to drop a new rotor in at some point. If I do, any recommendations on what I should replace this with for a simple swap without needing to add the ICM back in? I am trying to slowly inventory every part I donít recognize so if and when they go I know where to start.

You guys have been a god send and I really appreciate the time you haven taken to help me learn. Iím getting there ; )

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CSP 06-24-2018 04:00 PM

Yes, that is the Delco points distributor. No electronics involved.

John Strenk 06-24-2018 07:25 PM

yes and no.
They are simple, but points cam wiper (?) wears out and the dwell has to be adjusted often for best performance.
The contacts deteriorate and have to be replace depending upon how much you drive it.

Good ting to look up and read about.

Fourtrail 06-24-2018 07:42 PM

Pop the cap and see what is in there. Could get lucky and have a pertronix unit installed and be good to go with what you have.

BagusJeep 06-24-2018 10:51 PM

Almost anyone who has had points will tell you to go electronic, just so much easier to maintain.

Ditto on the Petronix, great product to take out the points. only way to tell is to lift the cap and have a look.

PottsyCJ5 06-25-2018 05:40 AM

Thanks for the info fellas. Iíll read up some more on dwell - Iíve skimmed over that section in my TSM but didnít really understand the importance of it.

Iíll grab a photo tonight with the dist. cap off, and look into the Petronix as well.

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PottsyCJ5 06-25-2018 06:01 AM

I just checked out the petronix on amazon and read some reviews. First off, Iím pretty positive I do not have a petronix, as I donít have any extra wiring coming from my distributor, and I have had the cap popped and didnít see anything that looks like the petronix in there.

That said, the reviews on the petronix are incredible and I think I want to switch to it in the near future. It sounds super simple to do - have any of you guys ran one of these? I really like that it doesnít seem to require an external ICM. It sounds like you just need to add the petronix itself and upgrade the coil? Is it really that simple?

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Matt1981CJ7 06-25-2018 07:13 AM


Originally Posted by PottsyCJ5 (Post 40258419)
It sounds like you just need to add the petronix itself and upgrade the coil? Is it really that simple?

You may not even need to upgrade the coil, but you'll have to confirm the amperage meets the Petronix specs.


PottsyCJ5 06-27-2018 05:43 PM

Finally got a chance to pop the dist. Cap and take a couple pics. Definitely not seeing anything that looks like a Pertronix under there. What am I dealing with? I noticed some crud in the second photo that doesnít look great.

Aside from going HEI, if this was your jeep, what would you do? Leave it alone and stick with this setup, or ditch the points and go with something like a Pertronix unit? The reviews are either amazing or terrible on the Pertronix.

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John Strenk 06-27-2018 07:01 PM

Yep, strictly a points distributor.

These are the points right here:

If you plan on keeping that distributor you might want to look on eBay for a Dwell Meter.

or put a Petronix in there.

The time now is 12:59 PM.

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