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No spark

Tiny
BNGRISS
  • MEMBER
  • 1976 JEEP CJ5
  • 3.8L
  • 6 CYL
  • 4WD
  • MANUAL
  • 200,000 MILES
Background: Vehicle sat for a while due to my job (roughly a year). Came home, put a new battery on it, fired right up. Changed all fluids, would start, then shuts off. Isolated the problem to a bad Ignition Control Module. The previous owner didn't care about how they "fixed" things. I had some time off, so I replaced some wiring and re-terminated some connections. Vehicle ran fine, then quit running. Found the coil to bed bad. Replaced it. No spark to the plugs. Replaced the distributor, got weak spark, but it wouldn't fire. Now, I do not have any spark. Everything that deals with the ignition is new, except for the actual ignition switch and the starter solenoid. I have +12 volts to the plug wire feeding the top of the distributor cap.

I believe the problem to be somewhere in the wiring. I hired a mechanic to get it running. They failed. They redid some of the wiring and now I am not sure what goes where. I would like to verify that all of the wiring is correct. However, I cannot find a diagram with proper colored wires. This is all the old Prestolite stuff. I am not ready to upgrade the ignition just yet. I have a few other things I want to fix on it first.

I believe the wiring from the the ICM is a great place to start. It has five wires: Black, white, blue, green, yellow. However, the plug it connects to has red, blue, green, yellow. I want to verify I have the plug side going to the right spots first. I know two of them go to the distributor, one to the Ignition, one to the coil, and the black to the ground (I have it grounded to the engine).

Sorry for the long post, I figured it would be best to give as much information up front as possible.
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Wednesday, February 27th, 2019 AT 6:39 AM

18 Replies

Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
More information the better!

I'm going to work on the wiring for you (may take a a day or so).

1) Right now let's give me the voltage on the positive side of the coil with the key "on"

2) The new generation will sometimes steer you wrong, let's insure the coil is for your system/ application. Many times they might ask you at the parts store, "external resistor or internal resistor". Yours will be "internal"

3) insure your module is grounded well on a shiny surface.

I'm pasting this part from another post I answered.

Paste

The problem with Prestolite is the wires are little "solid" copper wires going into the distributor (like really small bell wire), no matter how well you tie them up and support them they vibrate and break. Motorcraft uses stranded wire, I think it is 18 gauge.

Another problem it has is the darn "Bellows" contained in the white plastic (this is how the advance operates) will also split/ break/ get a hole in it. No timing advance and now a constant vacuum leak all in one shot. You will not know it until, you experiment with your timing gun, and see it does not advance!

The advance mechanism inside the distributor will bind due to it riding on plastic.

Modules just seem to not last.

On the upside! The coil never gave me a problem!

I just had enough of every time I turned around-

"Presto!"

I was not able drive Mr. Jeep!

Do you have tools?

A place to work?

At Hunter Army Airfield (1982-1987) Rec-services had a garage complete with two old dude mechanics to somewhat assist/ explain/ consult with your repairing. Bay space was $.50 a day, tool use required leaving your driver's licence with the tool room. I learned a lot there! You were not allowed to leave until the bay was spotless!

Since the distributor has been "out", I reckon I will talk you through verifying TDC (top dead center) once you return and we need to continue.

Your turn,

The Medic
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Wednesday, February 27th, 2019 AT 5:12 PM
Tiny
BNGRISS
  • MEMBER
  • 10 POSTS
Found my first problem. My coil has “external resistor use” labeled on the outside. Should I go ahead and replace before we continue?

The timing was set from TDC when I replaced the distributor.

I have all the tools needed to work and space. I have used the auto hobby shop for my truck many times.
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Thursday, February 28th, 2019 AT 4:44 AM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
The Jeep was running after you changed the distributor?

Is there a ballast resistor installed somewhere under the hood?

Again, key on, volts on positive side of the coil?

Save the old coil for when you decide to upgrade. :-)

Maybe some nice pictures - overhead/ left/ right sides of Mr. Engine with hood back on the windshield and the breather removed. Sometimes things get changed in forty years time. Sometimes I can spot an issue!

The Medic
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Thursday, February 28th, 2019 AT 4:57 PM
Tiny
BNGRISS
  • MEMBER
  • 10 POSTS
The Jeep hasn’t ran in a while. Been trying to isolate the problem to get a spark. So decided to replace everything to have a clean slate.

I haven’t seen a ballast resistor under the hood.

I will get pics and voltage first thing in the morning. I didn’t have a chance to mess with it today. Should I pursue an internal coil before proceeding?
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Thursday, February 28th, 2019 AT 6:29 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
Want to verify you have a 232 not a 258 straight six cylinder. (Kind of doesn't matter).

And, it has not run since the distributor was replaced? (Or even before that).

We will get you running, it's a bit frustrating "texting" a fix, than having your hands on it in real time.

Yes, obtain the correct coil!

I'll be here tomorrow (as always) waiting for your information.

Thanks,

The Medic
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Thursday, February 28th, 2019 AT 7:58 PM
Tiny
BNGRISS
  • MEMBER
  • 10 POSTS
I believe it is the 3.8L In-line six. The vehicle hasn't ran since I replaced the components. At first it was the Ignition Control Module, then the coil. I ultimately decided to replace everything except for the Starter Solenoid. I have always been able to get the engine to crank, but never to fire. I did have weak spark for a while, but now no spark at all. I tried to source the new coil locally yesterday, but everyone wanted to sell me an external resistor coil. I just ordered one from Crown and it should be here Monday. I tested the coil this morning and have 12 volts on the positive side.
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Friday, March 1st, 2019 AT 8:26 AM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
I really love "caps" and used them a lot in the past! Seems that a while back it was recommended that I not use them anymore!

If you want to verify "TDC" and the position of the distributor (rotor button).

I get carried away when I write, so if something does not make sense, just ask, I can usually come up with a different/ better explanation as time passes.

So, instead of copying and pasting or re-writing this long answer on here, I'm going to send you to it. Let's go about midway down to
SUNDAY, FEBRUARY 3RD, 2013 AT 8:29 AM (found at the bottom of answers). In this link.

https://www.2carpros.com/questions/1984-jeep-cj7-84-258-i6-weber-32-36-carb-tfi-igniton-upgrade-spark-been

I found this diagram in "Prodemand", it may help you too.

Use a little dielectric grease on your connections.

The Medic
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Friday, March 1st, 2019 AT 3:58 PM
Tiny
BNGRISS
  • MEMBER
  • 10 POSTS
That pic you uploaded appears to be the layout I am looking for. I am expecting the new, correct coil sometime Monday. I am out of town for work until Tuesday. I will verify all wiring and install the new coil when I get back.

I think I am good with TDC for the moment. I feel 100% confident that it is correct. I appreciate your help so far!
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Friday, March 1st, 2019 AT 6:45 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 43,339 POSTS
Please let us know what you find. We are interested to see what it is.
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Tuesday, March 5th, 2019 AT 10:15 AM
Tiny
BNGRISS
  • MEMBER
  • 10 POSTS
Meant to get back to you guys earlier in the week. Between work and personal stuff, I haven't had much time. I did get a chance to verify wiring last night. My ICM has four wires, blue, green, yellow, and white. These are terminated inside a four pronged plug. Two female and two male connections. On the vehicle side of the wiring, I have a similar plug, but with blue, green, yellow, and red with tracer. The diagram provided doesn't show a white. Should I assume that the white wire goes to the red with tracer wire? This is what I thought. However, on the side of the plug that goes into the ICM, the white corresponds with the yellow and the yellow with the red with tracer wire on the other end of the plug. Thoughts? The ICM did making a high-pitched sound after I connected everything. I immediately unplugged the connections to prevent damage.
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Friday, March 8th, 2019 AT 6:36 AM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
Whoa!

Looks like CJ MEDEVAC may have pulled another one out of his sleeve!

This one do you a little better?

The Medic
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Friday, March 8th, 2019 AT 4:37 PM
Tiny
BNGRISS
  • MEMBER
  • 10 POSTS
That definitely helps! I just got back from a family trip (took the ball and chain to Florida for a concert last night). Told the wife I’m headed to the garage and to only bother me if the sun is coming up.

I ensured everything was connected as your picture shows I hooked on the paper clip and grounded it to the engine. I was able to get spark. I did the alligator clip from the starter solenoid to the positive side of the battery.

I’m charging the battery at the moment. Then I am going to test for spark from the distributor to the plug in cylinder one.

Oh yeah, tightened every screw and verified every mechanical connection involved with the ignition.
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Saturday, March 9th, 2019 AT 2:37 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
Roger,

We're not going anywhere, so keep us posted.

A picture of your Jeep would look nice in your post!

The Medic
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Saturday, March 9th, 2019 AT 3:02 PM
Tiny
BNGRISS
  • MEMBER
  • 10 POSTS
Alright. Everything checked out as far as wiring goes. However, Crown sent a “external resistor” coil. I called their customer service and they stated I required an external resistor coil. If my memory serves me correctly, I did have a resistor on there at one point. After speaking to the wife, she said she might have threw something similar to a resistor away when I re-did some of the wiring. Now, I have no idea where the resistor would go. Any help in that area? I uploaded some pictures too. I will be following up shortly with a current wiring diagram of what I have going on. I hope to get this resolved in the next two days because I have to go out of town for about thirty days or so.
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Sunday, March 10th, 2019 AT 4:49 PM
Tiny
BNGRISS
  • MEMBER
  • 10 POSTS
Current wiring. See anything wrong? Need a better picture? Where would the ballast resistor go? Between I and positive coil side?
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Sunday, March 10th, 2019 AT 5:16 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
Solenoid is right. (Drawn diagram)

If you have the correct coil, there is no ballast resistor at all ever 1976-1978!

There is no resistance wire for Prestolite.

There is a capacitor shown at the coil.

Your pictures

1) Is the connector all the way in or is the skirt crumbling off appearing like that?

2) Second red wire on "S" is a temporary way to crank?

3) Wrong coil, should have internal resistor (specific for your Jeep)

4)

5)

6) Nice Jeep!

Your question:

Where would the ballast resistor go?

When upgrading, it would be on the wire to the positive side of the coil. (Only reducing the coil) (Not before other wire intersections)

The Medic
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Sunday, March 10th, 2019 AT 6:06 PM
Tiny
BNGRISS
  • MEMBER
  • 10 POSTS
1) Is the connector all the way in or is the skirt crumbling off appearing like that?
Yes, the connector is all the way in. I am not sure why it looks like that. I made it a point verify it.

2) Second red wire on "S" is a temporary way to crank?

Yes. I jumped from the "S" to the positive side of the battery. I was doing this when testing for spark by pulling a plug and grounding it. I should have taken that off before I took the picture

3) Wrong coil, should have internal resistor (specific for your Jeep)

Can you reference a part number for me? I will go buy one today. Unfortunately, everywhere I am going to is giving me the external type.

4) Question was blank.

5) Question was blank.

6) Nice Jeep!

Thanks! The family and I really enjoy cruising in it.

When you say on the positive side of the coil. Is that from the ignition wire or from the ICM wire?
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Monday, March 11th, 2019 AT 9:09 AM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
Positive (and negative) side of coil is marked on the top near the terminals.

Here's one:

https://www.autozone.com/ignition-tune-up-and-routine-maintenance/ignition-coil/spec-ignition-coil/883605_0_17367

Here's another:

https://www.autozone.com/ignition-tune-up-and-routine-maintenance/ignition-coil/duralast-ignition-coil/111849_576402_17367

Not meant for you! (Yet!)

When I upgrade, I use all of the ignition parts as a 1979 would have, this cuts down on mismatching/ confusing stuff during a later repair/ tune up.

Here's a diagram for upgrading to Motorcraft from a '76, '77, '78

Beings that those years did not have a "resistance wire" as does a '79 on up. The ballast resistor takes the place "that special wire"!

It's installed nearer to the coil on the wire that feeds the positive side of the coil (we don't want to reduce anything else back towards the firewall!)

Notice the ballast resistor feeds right to the "Tee" at the coil. "I" terminal feeds to the other side of that "Tee". The explanation on my diagram should explain how "I" helps while cranking.

The Medic

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Monday, March 11th, 2019 AT 3:47 PM

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