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Prestolite ignition DIED..!!

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BrotherBamc View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BrotherBamc Quote  Post ReplyReply Direct Link To This Post Topic: Prestolite ignition DIED..!!
    Posted: Nov/28/2021 at 5:14pm
1977 Jeep CJ5 with a 304. Pretty much stock except for some fender well exit headers and some glass packs on the end of the headers. 
Gave it a bath today and something either got wet or something shorted and took a big fat dump. 
Changed the plugs, plug wires, cap and rotor. Still no spark from the coil. 
Reading the TSM I'm supposed to have 2 wires coming from the dizzy. But I only have 1.
I've checked resistance of the ignition feed wire and we got 1 ohm as its supposed to. Checked resistance of coil primary (coil pos. to neg.) 1.8 ohms. In spec.
Checked resistance of coil secondary and I have 6.2 ohms. Supposed to be 9,000 to 15,000 ohms. 
Did I fry the coil or the ECU..?? 
Any other alternatives to the prestolite besides replacing the dizzy or going pertronix..?? (Can't find a pertronix that fits right now either probably still on a boat) Ouch
Any ideas besides start throwing more parts and money at it..?? 
Thanks..!! 

77 CJ5 360
73 Gremlin 401 4 speed
2006 Dodge Magnum R/T AWD
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tufcj View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tufcj Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2021 at 7:17pm
The 77 CJ Prestolite will have a ECM on the passenger inner fender (maybe 4x4x1" gold box).   1st, make sure the ground wire for the ECM is good.  If that's good and the 4 prong connector is clean, try to find a new ECM.  They are notorious for failing with no warning.  After the second failure in my 77, I started carrying a spare in the glove box.  After the 3rd failure, I went to a Mallory Unilite and never looked back.  The ECM is potted, and there,s no way I've heard of to test, so you'll have to replace it.

Bob
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BrotherBamc Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2021 at 7:34pm
Thanks Bob...
That's what I'm doing. Going unilite. 
I think I've found enough pieces to put something together...

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Post Options Post Options   Thanks (1) Thanks(1)   Quote sweatlock Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2021 at 8:08pm
There was a factory TSB (Technical Service Bulletin) put out by AMC that stated to cut off the male/female connectors on the two wires coming out of the distributor and soldering them together with heat shrink. It was a known failure point. Yes, the ignition control unit on the fender is another problem point - I remember that whenever I went into a junkyard back in the ‘80’s if I found one I would snag it for my ‘77 Pacer and I would always carry a spare with me. 

AMC went to a Ford Duraspark ignition system in ‘78 for good reason. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote rgsauger Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2021 at 10:32pm
I have the Duraspark in my CJ.   I use it to trigger an MSD 6a box and it feeds into an MSD blaster coil. Could not be more satisfied. Has been in my rig for over 20 years and performs flawlessly. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Nov/29/2021 at 12:24am
DuraSpark is pretty good, other than the pita involved in re-curving one.
Still prefer the lack of "radiall proximity sensitivity" of a UniLite Infrared Module over any HAL effect, magnetic, points, etc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2021 at 1:53am
I cannot complain about Prestolite. I have 50,000 relatively trouble-free miles on my Prestolite ignition. One module started misfiring slightly at idle on hot days and had to be replaced and I had an ignition coil die once. 

I've had far more problems with Duraspark. I hate Duraspark. It has left me on the side of the road with the hood up 2 or 3 times too many for me to trust it any more.  

Prostolite is beautifully simple and effective. There should be two wires leading from the distributor to the ignition module. Just keep the wires in good shape and the connector clean and tight with dielectric grease and it'll be just fine. They are small wires, so be careful. Keep them protected inside a wire loom or sleeve. 

The ignition coil with Prestolite is a conventional points-type ignition coil. It should measure way more than 6 ohms on the secondary side. 9000 ohms is more like it. It sounds like you have a shorted secondary winding in the coil. Try a new coil.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2021 at 5:23am
A module:
And I used to take the old ones off, wire wheel the epoxy and metal housing, flush with WD40, heat in the oven for an hour at 120 degrees or so to drive out any moisture (do this when the wife is not home!!!), test it on a vehicle, and if OK just epoxy seal it back up as a spare.
75% of the time just driving out the moisture would make a serviceable box.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fluffy73 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2021 at 6:22am
My V8 Hornet originally came with Prestolite.  I never drove it like that. I had access to a distributor machine way back then so, I plunked in a recurved points distributor.  Really woke the 304 up.  Today, it's got a Pertronix.

A former acquaintance of mine had a '76 Hornet with Prestolite. She barely had the car a year and several times it wound up on a roll back, being brought to my house so I could swap ignition modules. I think that car went through 3 or 4 of them.  A few years later, a friend of mine wound up with the car, not running.  I hadn't let on that I knew the car, and mentioned he should change the module.  He did not believe me and went through everything trying to get the car to run.  Until one day, he was so frustrated and about to part the car out, I dug in his collection of parts, found the first module I could and threw it at him.  The car fired right up.   Funny thing is, he still parted that car out. I wound up with the fenders and the big gas tank.  One of these days I'll swap my Hornet over to the bigger tank.  Those fenders got cut up and used to patch my Gremlin.

My Eagle SX/4 and several other friends who had Eagles.... we all had the Duraspark. Never an issue. I've heard of so many people (especially Ford folk) who hate them and yet, mine was super reliable.
I am genetically incapable of being Politically Correct.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BrotherBamc Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2021 at 10:06am
Have a new coil on its way.
Just have to pull the old distributor out and get the gear off. 
Wiring is a complete mess, both under the hood and under the dash.
No turn signal on the right front and NO turn signals when the lights are in the on position. Something is not right somewhere...
Just gotta love someone else's mess... Ouch
77 CJ5 360
73 Gremlin 401 4 speed
2006 Dodge Magnum R/T AWD
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