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Unread 07-12-2014, 07:28 PM   #1
sabbyATL
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75 CJ5 w AMC 304 - weird start problem

So, I'm back. With a seemingly new problem.

Oh, and I have a 74 CJ5, not a 75. Typo in the thread title. But it does have the AMC 304.

Last weekend and early this week my Jeep drove fine. It's always had a bit of a sluggish start and if the battery cables are loose it sometimes won't start. I say this because on Tuesday we had an issue with it not starting and I went under the hood and wiggled the cable and it started.

Today when we went to start it there was nothing, not even the radio came on. I popped the hood and found the cables to be nice and tight.

I pulled out my multimeter and checked the charge across the battery and it was showing something like 6 and some change.

After a moment I noticed something weird about the ignition coil, which I replaced in late April of this year. I checked the charge to the coil and it was nothing - zero.

The weird thing I noticed about it was that it seemed like it had melted (see pics).

I took the battery to the auto parts store and they tested it and said it was dead dead dead bad bad bad.

So, I bought a new battery and a new coil. I also bought new battery cables because the old ones were a little ratty with exposed threads.

I replaced the cables, installed the battery, and then set to work taking out the old coil.

Let me tell you...that coil was HOT. Blistering hot. And I hadn't run the Jeep since Tuesday. I am not sure how it got hot right there that day.

So, here we have a dead battery and a super hot melted ignition coil. I don't know if that happened when we went to start the Jeep this afternoon or if that was happening on its own or what.

So, I replace the coil.

Went to start it and here is what happens:

1. In Run the dash gets power.
2. In Start it cranks and turns over and catches.
3. It immediately dies after one little engine rumble.

Almost like it has no fuel to keep going, but there's a good quarter tank left. And I turned on the electric pump for good measure. I get the same sequence as above.

I took my multimeter and tested the battery - 12.5V.
Then I turned the starter on Run and tested the positive side of the solenoid - 12.44V
Then I tested the positive side of the new coil - 5.6V

That's all I did because it was getting dark and I had plans.


So, can anyone help me figure out what's going on and I'll go fix it?


This forum has been so much help in the past so it's the first place I've come to.



Thanks!

Jen

20140712_192343_zpsrjvnj0al.jpg   20140712_192348_zpsw9hddcu7.jpg   20140712_192409_zpsujjmlpes.jpg  
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Unread 07-13-2014, 08:37 AM   #2
sabbyATL
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Can anyone help me?

The current issue is that when I try to start my CJ5 it cranks, turns/catches, and dies after the initial fire. This all started after findino the battery dead and the coil melted. Both are replaced.
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Unread 07-13-2014, 09:27 AM   #3
Mike Romain
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Is the coil still getting real hot? A short in the alternator can sometimes cause that.

You also might have melted the ballast resistor if yours has such. I would turn the key to run and see what the volts are on the coil positive. The coil gets a different power in start.

I would also try unplugging the alternator to see if it runs.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 07-13-2014, 09:48 AM   #4
sabbyATL
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Quote:
Originally Posted by Mike Romain View Post
Is the coil still getting real hot? A short in the alternator can sometimes cause that.

You also might have melted the ballast resistor if yours has such. I would turn the key to run and see what the volts are on the coil positive. The coil gets a different power in start.

I would also try unplugging the alternator to see if it runs.
Just felt it - cool.


The ballast resistor looks fine but would it be obvious?

So, assuming I got it right that Run is like Accessory where it gives power to the dash and under the hood but doesn't start the engine then I can tell you that the coil had 5.39 on the positive end.
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Unread 07-13-2014, 09:51 AM   #5
sabbyATL
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Oh, and the carb is getting fuel. Just checked.
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Unread 07-13-2014, 09:55 AM   #6
sabbyATL
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Thanks, by the way. Thanks A LOT!
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Unread 07-13-2014, 10:00 AM   #7
Mike Romain
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Quote:
Originally Posted by sabbyATL View Post

Just felt it - cool.

The ballast resistor looks fine but would it be obvious?

So, assuming I got it right that Run is like Accessory where it gives power to the dash and under the hood but doesn't start the engine then I can tell you that the coil had 5.39 on the positive end.
I would unplug the alternator and then see what the coil reads.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 07-13-2014, 11:13 AM   #8
sabbyATL
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Quote:
Originally Posted by Mike Romain View Post
I would unplug the alternator and then see what the coil reads.
Ok, sorry this took so long. Was also doing laundry.

And I'll be going to a pup down the street around 3 to watch the finals in the World Cup so I'll have to take another break. I don't really drink so I'll be good to work on it later.

Anyway, disconnected the alternator from the solenoid and tested the coil, showEd 5.41V.
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Unread 07-13-2014, 11:29 AM   #9
sabbyATL
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Ok, here are some readings:

Across battery - 12.37V
Solenoid - 12.36V
Alternator - 12.36V
Coil (alternator to solenoid) - 5.97V
Coil (alternator detached from solenoid) - 5.91V
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Unread 07-13-2014, 11:30 AM   #10
sabbyATL
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Does this mean the solenoid is bad?
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Unread 07-13-2014, 11:36 AM   #11
sabbyATL
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Never mind about the solenoid.

I tested the ballast resistor and found 12.17V on the right side (facing the resistor) and 11.87V on the left.
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Unread 07-13-2014, 11:43 AM   #12
Mike Romain
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Quote:
Originally Posted by sabbyATL View Post
Never mind about the solenoid.

I tested the ballast resistor and found 12.17V on the right side (facing the resistor) and 11.87V on the left.
That is good. Now why is that 11.87 not making it to the coil? Could the plug at the coil have gotten burnt too?
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 07-13-2014, 11:49 AM   #13
sabbyATL
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So, from what I read the ballast resistor should reduce the voltage to the coil, which it appears it's doing. I don't know if going from 12 to about 6 is right but that seems to be what's happening.

I want to reiterate that there IS spark.

The engine does actual start but it just dies immediately after starting. As if there is no fuel to keep combustion up or something. But I can tell you the carb is getting fuel. And I don't know how a fuel problem could be related to the battery and coil having a meltdown.
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Unread 07-13-2014, 11:50 AM   #14
sabbyATL
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Quote:
Originally Posted by Mike Romain View Post
That is good. Now why is that 11.87 not making it to the coil? Could the plug at the coil have gotten burnt too?
The one at the top of the coil?

It's possible. The top of the old could was crumbling away from the heat damage.
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Unread 07-13-2014, 12:01 PM   #15
sabbyATL
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It looks fine to me.

Order of photos is:
Plug on new coil
Inside of plug
Old coil
20140713_135126_zpsguimndf3.jpg   20140713_135234_zpswffywpnf.jpg   20140712_192343_zpsrjvnj0al.jpg  
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