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-   -   Prestolite ICM - Not Required for this setup?? 75í CJ5 304 V8 (https://www.jeepforum.com/forum/f8/prestolite-icm-not-required-setup-75-cj5-304-v8-4313845/)

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.

https://uploads.tapatalk-cdn.com/201...dd99771a7c.jpg

https://uploads.tapatalk-cdn.com/201...cfbd88782e.jpg


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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.

Matt

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.

https://encrypted-tbn0.gstatic.com/i...E3WzuD6BppLZ8M

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.

Matt

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

Reliable?
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

Quote:

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.

Matt

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.

https://uploads.tapatalk-cdn.com/201...31e78601b0.jpg

https://uploads.tapatalk-cdn.com/201...3772f9f007.jpg

https://uploads.tapatalk-cdn.com/201...b41cce43bb.jpg

https://uploads.tapatalk-cdn.com/201...0c6c3e0e2e.jpg



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John Strenk 06-27-2018 07:01 PM

Yep, strictly a points distributor.

These are the points right here:

http://uploads.tapatalk-cdn.com/2018...3772f9f007.jpg

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

or put a Petronix in there.

Matt1981CJ7 06-28-2018 03:48 AM

Personally, I'd ditch the points, and stick a quality HEI or CDI system in there.

Many guys prefer the HEI because of the easy one-wire install. You can eliminate the existing coil and any old ignition modules, because those things are built right into the HEI distributor. There is a minor gear engagement issue with HEI, due to its design. It doesn't engage the cam gear as fully as a stock distributor does. Jeephammer claimed this could cause premature gear wear, but a ton of guys run HEIs with no problems.

I prefer the separate components of a CDI system and a distributor that is designed specifically for my engine. My system is all MSD products.

The HEI vs CDI debate will probably rage forever. The truth is, you probably wouldn't notice a lick of difference in performance between the two, and they're both a big upgrade over points.

Matt

PottsyCJ5 06-28-2018 04:18 AM

Thanks Mat and John. Iíll look into how to adjust to the dwell for now, and also start going down the rabbit hole of researching what ignition system I want to go with now that I know what I am starting off with.

Iíve heard great things about MSD. The stuff with the cam gears on the HEI systems scare me to be honest though. The petronix is a little pricey but not bad for a single unit. The earlier models are cheaper now that the petronix III is out it seems, and I might be fine with the Ignitor II series. At some point down the road I may just try that route for simplicity sake for myself, and see how it goes. Iíve bought enough meters for now and donít feel like investing in a dwell meter if Iím ultimately going to want to ditch the points anyway.

Thanks a lot fellas.


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PottsyCJ5 06-28-2018 10:44 AM

Sorry, couple more questions... lookin at these petronix systems is a little daunting having never done any ignition work before. I am trying to price out the petronix and I am not sure what I need. Since the PO swapped the stock prestolite distributor for the AC Delco Points distributor, is this the correct petronix to buy if I want to convert my current dist over to electronic?

PerTronix 91281 Ignitor II Adaptive Dwell Control for Ford 8 Cylinder https://www.amazon.com/dp/B000JUT7RS..._c4qnBbZM3TPZ9

Iím not sure I need the Ignitor III though I am considering going that route to get the multi-spark technology. This isnít a performance rig, I just want to get all the power I can out of my 304 and switch to a setup that requires les maintenance (and is fairly simple to install).

Also, when I adjust my timing the distributor was REALLY hard to turn. Is that common or should I be concerned? When Iíve watched videos of people timing their engines it looks pretty effortless to turn the dizzy and mine took a pair of vice grips to get to turn. Because of that I was considering switching out the whole distributor with a petronix dizzy with the igniter ignition built in, BUT one summit it mentioned for AMC engines itís recommended to swap out the cam gear when changing to their distributor. That is more involved than I am trying to get at this stage in my Jeep journey.

Sounds like I should upgrade my spark plug wires as well, which I was planning on doing anyway.



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Matt1981CJ7 06-28-2018 10:50 AM

Did you loosen the hold-down bracket at the bottom of the distributor before attempting to change timing?

Sorry, I can't help you with your Petronix questions, as I've never used one. I view it as a bit of a bandaid solution, anyway.

Matt

PottsyCJ5 06-28-2018 10:56 AM

I did loosen the hold down clamp, Matt. Thanks.


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Matt1981CJ7 06-28-2018 11:09 AM

Then something is amiss with your distributor. With the hold down bracket loose, it should turn easily.

I'd find TDC of #1 cylinder, then pull the distributor. Hopefully the problem is internal to the distributer and not a gear mesh problem.

Good luck,

Matt

PottsyCJ5 06-28-2018 01:42 PM

Prestolite ICM - Not Required for this setup?? 75í CJ5 304 V8
 
Ugh, yeah it was seriously difficult to turn. Everything seems to be functioning fine but it was scary hard to turn.

The whole thing should turn correct? as in not something inside the shaft is what turns, but the entire assembly spins? I literally had to put vice grips on it and pull with all my night to budge it. I was able to get the timing adjusted 5 degrees eventually by turning, but I almost gave up for fear I was breaking something when it budged enough to move it. I figured there was just rust or crud on the shaft, but didnít consider the gears.


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Matt1981CJ7 06-28-2018 02:49 PM

Yes, the whole distributer should turn quite easily.

Hopefully the distributor shaft bore is just corroded, making it difficult to turn. You'll know when you pull the distributor out. You should be able to spin the distributor shaft/gear with your fingers easily.

Matt

PottsyCJ5 06-28-2018 03:28 PM

Thanks bud.


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RedNeckCorvette 06-28-2018 04:10 PM

I have had a distributor shaft lock up in the past on a 400 Ford. I feed it penetrating solvent for several weeks wile hitting it some place on the pot metal with a light plastic hammer. Tap it around, up and down to let the fluid do it's thing. Sooner or later it will give, most of the time.

If you change the distributor over to HEI or what ever else? Take the gear off the bottom of your old distributor and put it on the new one. Most of the time this requires you to push out one retainer pin on each gear, then just switch the gears. The old goes on the new distributor and now it matches the wear pattern on the cam exactly. Lay them side by side and check the overall length. If ever, rarely [I have never seen it] there may be a difference. Nothing to it really.

RN

PottsyCJ5 06-29-2018 07:08 AM

Prestolite ICM - Not Required for this setup?? 75í CJ5 304 V8
 
Hey thanks man, that sounds like solid advice. I have been hesitant to touch the dist. after getting it timed for this reason. If I can reuse the current distributors gear and not have to replace the cam gear, I may considering going for a petronix like distributor instead of just the module.

Swapping the gears between distributors wonít change the behavior of the new distributor? Like screw up the timing or anything? I mean I know Iíll have to retime it, Iím talking about the new one spinning at a different rate than designed if the gears donít have the same profile or whatever.

I know I read some of the HEI dizzys out there use a hardened gear which chews up the cam gear too, so this seems like a good option for peace of mind to avoid that.


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Matt1981CJ7 06-29-2018 07:58 AM

Potts,

Yes, you have to be careful about mismatching certain HEI distributors that have a gear that is hardened more than the factory cam gear. This is especially the case with AMC V8s because they have a detachable cam gear that is softer than the cam itself. On the I6 engine, the cam gear is machined into the cam, which is already hardened, so it's less of an issue.

As long as you have a matching set of gears suited for your engine, it won't affect the function of the distributor. The distributor gear spins only as fast as the cam gear makes it spin.

Hope this helps,

Matt

PottsyCJ5 06-29-2018 07:01 PM

That does help, Matt. Thank you. Itís funny, I started this thread just to make sure I could disconnect my ICM, and by the way of it learned enough about my ignition to convince me to swap out my points and go electronic. Man working on this jeep is addicting.


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John Strenk 07-01-2018 06:30 PM

There is a special kine of therapy for that kind of addiction. It's called B.R.O.K.E.

Matt1981CJ7 07-01-2018 09:09 PM

Quote:

Originally Posted by John Strenk (Post 40265669)
There is a special kine of therapy for that kind of addiction. It's called B.R.O.K.E.


LOL. The Warden said she'd Nutter me if I spent any more on mine. >:)

Matt

CSP 07-03-2018 10:34 PM

Quote:

Originally Posted by PottsyCJ5 (Post 40262303)
SI am trying to price out the petronix and I am not sure what I need.

Your application would be any '72-73 CJ with the AMC 304 engine.

John Strenk 07-04-2018 07:42 PM

Quote:

Originally Posted by CSP (Post 40268419)
Your application would be any '72-73 CJ with the AMC 304 engine.

Would that give him one for an AMC distributor or should he choose a different application because he has a GM distributor in there?

PottsyCJ5 07-05-2018 05:56 AM

Going broke indeed John and my wife is starting to reach her limits for how much Iíve been in the garage. Gotta start spacing out my Projects better and alternate home projects in between ; )


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John Strenk 07-05-2018 01:00 PM

Quote:

Originally Posted by PottsyCJ5 (Post 40269675)
Going broke indeed John and my wife is starting to reach her limits for how much Iíve been in the garage. Gotta start spacing out my Projects better and alternate home projects in between ; )


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Your jeep is running, Redo her Kitchen. Then get back to the jeep later....

CSP 07-06-2018 09:54 PM

Quote:

Originally Posted by John Strenk (Post 40269433)
Would that give him one for an AMC distributor or should he choose a different application because he has a GM distributor in there?

Jeep used an AMC variant of the GM distributor in the early 70s, prior to Prestolite. This is what his engine has in it currently.

It's the same concept as '78 and up CJs having the AMC version of Ford's Duraspark dizzy.

PottsyCJ5 07-10-2018 05:51 AM

Update on this...it seems removing the ICM has caused my battery to start draining. Jeep left me stranded twice.

The Jeep was starting and running fine for two weeks with very minimal driving (probably only a couple trips) after taking out the ICM. The ICM only has two plugs - one single wire plugs that connects directly to the starter solenoid, and another with 4 wires that connect with a plug into a harness and I canít tell for sure where it goes from there.

I suspect what is happening is that when the PO switched back to a points dizzy, the wiring was not changed and the ICM wiring is somehow in the circuit the alternator useds to charge the battery. Since taking the ICM out and not changing any other wiring the battery was not charging while driving. Battery is only a couple months old so I think it took a bit to drain completely making this not immediately apparent.

Does that make sense or do you think I have something else going on? Jeep had never left me stranded or had any starting issues prior to this and starts on the first go when the battery is fully charged. A jump from my truck got me back on the road both times and I have been leaving the battery on a trickle charger, and it will hold 12 volts after being charged. The battery issues definitely seem directly related to removing the ICM.

For now I just put the ICM back in as well, though this time I put a piece of cardboard under it to act as a heat sink to hopefully stop the oozing.

Side note - Would fully draining the battery reduce its life? It was a new Napa battery and I hope I didnít cook it.


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Matt1981CJ7 07-10-2018 06:31 AM

The old ICM should have nothing to do with the charging system. I think you have other issues going on.

FYI, the 4 wires from the old ICM should be as follows: Green and red w/tr wires went to the old coil, yellow and blue wires to the old distributor. As I stated earlier, the old ICM and all if those wires can be removed without causing any problems.

Do you have a test light? If so, disconnect the negative battery cable. Attach the test light clamp to the cable and touch the probe to the neg battery post. If the light goes on, you have a parasitic drain that you need to hunt down.

Matt

John Strenk 07-10-2018 07:08 AM

1 Attachment(s)
Well looking at the schematic, it shouldn't matter.

Did you just unplug the one on the left?
https://uploads.tapatalk-cdn.com/201...cfbd88782e.jpg

The one on the right controls the charging.

Here is a schematic of your 1975 charging circuit for a V8.
It looks as if there is a sense wire that is attached to the power input to the ICM.
But disconnecting it should not effect the charging.

Unless he ran new wires to power the coil and cut out a lot of that circuit.
But then it would of not worked at all.

Is it charging with the ICM hooked up? Verified with a volt meter?

PottsyCJ5 07-10-2018 08:41 AM

Prestolite ICM - Not Required for this setup?? 75í CJ5 304 V8
 
Matt - I do have a test light and a multimeter. I will try that test as soon as I get home. So I connect the test light to the negative battery cable and directly to the negative battery post?

John - yep, I only disconnected the box on the left. In that photo you can see the 4-wire plug is already disconnected and then I also disconnected the smaller black wire you can see in that photo that connects to the solenoid middle left post (I forget if that post is the ďIĒ or the ďSĒ post).

What is the best way to test if the battery is being charged with or without the ICM plugged in? I want to test the output at the alternator but not sure which terminals to test with the multimeter. And how can I test that the current is actually making it back to the battery when engine is running and the battery should be charging?

Temporarily I have plugged the ICM back in until I can find out whatís going on. This definitely started right after disconnecting the ICM, but I understand it ďshouldnítĒ be related.


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Matt1981CJ7 07-10-2018 08:52 AM

Quote:

Originally Posted by PottsyCJ5 (Post 40276037)
Matt - I do have a test light and a multimeter. I will try that test as soon as I get home. So I connect the test light to the negative battery cable and directly to the negative battery post?

Connect the test light to the disconnected negative battery cable, then touch the test light probe to the negative battery post. If the light goes on, you have a parasitic drain.

To test the alternator voltage output, use your multimeter at the battery first with the engine idling. You should have around 14.4 volts. Then test the large red wire at the alternator. It should have the same voltage, or very close.

Matt


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