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Cranks, but does not start

Tiny
BRADEN99
  • MEMBER
  • 1982 JEEP CJ7
  • 4.2L
  • 6 CYL
  • 4WD
  • MANUAL
  • 100,000 MILES
Fuel is getting into the carburetor, and worked okay before, but there does not appear to be any spark coming from the coil. This happened after it had run for about ten minutes perfectly as we were taking it to the emissions testing facility. It had to be turned off briefly for whatever reason, and then never started again.
We replaced the ignition coil, to no avail. I think it had an ECU originally, but it appears to have been bypassed, which may need to be fixed to pass emissions, but at this point, it would just be great to find out why it suddenly stopped working. Any tips or help would be amazing, as I am 19, and do not have a ton of experience working on old cars for obvious reasons.
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Sunday, July 15th, 2018 AT 6:44 PM

8 Replies

Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,005 POSTS
Check your fuses.

Check the connections at the solenoid (a wire could have broke off of a ring).

It may also be several other possibilities.

Key "on", what is the voltage at the positive side of the coil? Picture 1.

Failed ignition module? Not sure what you have now (if modified). Can you send a picture? (Even pictures of the whole engine with the breather removed)

Coil failure?

Pickup/or distributor wires within the distributor?

Rotor not turning?

Just for giggles, try this! This may rule out things or rule in things! See last two pictures. Positive battery terminal to the positive coil terminal using a jumper wire. Attempt to start it up. Return with your results!

I am here to help as long as you keep responding.

The Medic
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Sunday, July 15th, 2018 AT 7:46 PM
Tiny
BRADEN99
  • MEMBER
  • 5 POSTS
Thanks so much for the reply! I just went out and took some photos, and checked the fuses.
The voltage on the positive side of the coil was 6.3 volts.
Fuses were all fine
The rotor was turning perfectly, and did not show signs of wear on the distributor.
I will try your last two photos tomorrow. How many amps is the fuse that you have attached?
Hopefully the attached photos will give you an idea as to what I am up against, and it is certainly not pretty. I have quite a bit of knowledge on circuitry and electrical components, but this is all quite messy and confusing.
I am also considering reattaching the ECU (I believe it is the box on the left with all the unattached wires, but it does not look like the original, as I have looked around online for clues as to what the box is.
Thanks again, and have a great night!
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Sunday, July 15th, 2018 AT 8:15 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,005 POSTS
Good pictures!

Thing on left is a voltage regulator, probably once used with a Motorcraft alternator. Appears to be space junk now.

You are looking for this (picture 1).

Grab the wires on either side of the connector and pull, this is the correct way to take it loose, prying the tabs will break them off.

If my test does not work (that is a 15 amp fuse- just a little protection on my test lead) pull the ignition module out and have it tested.

Have them test it five or more times- they will trick you!

If a new one is needed- test it too, before you leave! Nothing like the "fine, brand new one" not working too! This would result in chasing the wrong stuff for a fix. Been there!

Picture 2 is the test machine at Advance Auto Parts.

You just pulled into our garage, this is the first impression, Do not fret, we will get to a solution with more testing if needed.

I want to know what coil you got and from where. It may matter!

Green wire at the coil (loose one) where does the other end go?

What is the voltage on the positive side of the coil while cranking?

Just trying to put in a lot in in a short time!

The Medic
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Sunday, July 15th, 2018 AT 8:44 PM
Tiny
BRADEN99
  • MEMBER
  • 5 POSTS
Oh, okay. Voltage regulator makes much more sense, lol. I still have no clue where, if it even exists, the control unit is located, but that is not a priority at the moment.

I tried your test using a ground wire, so that negated the need for a fuse, and it almost seemed like it was shorted, as it made quite a few sparks when connected to the positive terminal of the battery and warmed up the heavy gauge wire (12, I believe), but maybe that is correct. I accidentally left the ignition turned on last night, so I attempted to jump start it, which did not work. It did crank just fine, however.
I tested the starting voltage to the starter as I saw in the manual, and got 9.5 volts instead of the full 12, which I believe should be what is being supplied.
I am currently waiting for the battery to charge before continuing.

I have no clue where that green wire goes, and I have that problem with many of the wires in the truck go, as they are all unmarked. I might try to see if it is getting any voltage.
I will take out the ignition module tomorrow and get it tested if I am able to locate it.
Thanks again!
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Monday, July 16th, 2018 AT 5:07 PM
Tiny
BRADEN99
  • MEMBER
  • 5 POSTS
Found the ignition module, and it is in pretty nasty condition. Looks like coolant has been leaking on it, and there is a puddle on the plate underneath. If this is in fact the problem, I might just move it to a different, higher location, because I honestly cannot imagine why they would do that where water could reach it so easily.
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Monday, July 16th, 2018 AT 5:40 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,005 POSTS
Starter voltage will probably be fine with a fully charged battery.

The goo on the ignition module may be the gel they pour in the bottom to protect the electronics. It is supposed to remain firm and intact, heat and time makes it drool out.

If you do move the module, insure you scrape the paint under the mounting bolts, the module's body needs a good ground.

I have mine on the passenger side fender, under my train horn (cannot see it in my picture)

Green wire - trace it down, it may go to the coil, we do not want to just hook it on without knowing what it is. That is a good way to fry something else and quadruple our problems!

Is it possible that you left it off when you changed the coil?

Did you get the coil information I requested?

The Medic
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Monday, July 16th, 2018 AT 6:20 PM
Tiny
BRADEN99
  • MEMBER
  • 5 POSTS
Here is a photo of the inside of the ignition module. It is pretty wet, but I also see the gel. The other photo is the package that the coil came in.
It is possible that the wire went to the coil, I will trace it in a moment.
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Monday, July 16th, 2018 AT 6:29 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,005 POSTS
Coil is correct for your rig!

A OEM would have been just fine too.

The Medic
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Monday, July 16th, 2018 AT 6:58 PM

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