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Unread 06-07-2011, 07:08 PM   #1
risgate1
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1985 CJ7 
 
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CJ not running - electrical gremlins

i am at my wits end. i was freshening up my 85 CJ (with a swapped in 304), getting her ready for the summer. I took off the front end and shot the engine bay with paint, and put in a bunch of new parts.

I started her up, she ran like a top, took her outside and all of a sudden she died. i will turn the key, she fires for a second, then quits. I looked and saw some fried wires at the starter solenoid - evidently it wasnt grounded good enough. So, i changed out the solenoid and grounded it to the battery, that didnt work, same result. Then i changed out the alternator thinking i fried it, but that didnt work either. I am assuming at this point it is a fantom ground that got fried. Does anyone know where i should be looking at this point from a wire and ground standpoint?

i figure it has to be an issue prior to the ignition coil because if i keep the starter engaged the engine runs until i turn off the key (bad for the starter i know).

any suggestions please! thanks in advance

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Unread 06-07-2011, 07:13 PM   #2
benullman
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check the ignition module. It may not be good and isnt giving the fire, signal

Ben
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Unread 06-07-2011, 07:14 PM   #3
risgate1
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ben

where is the ignition module located?
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Unread 06-07-2011, 07:45 PM   #4
benullman
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Quote:
Originally Posted by risgate1 View Post
ben

where is the ignition module located?
drivers side fender by the overflow tank and washer fluid tank

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Unread 06-07-2011, 07:45 PM   #5
Alby63
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Check for power at the coil+ with the key in the on position. If you still have the resistor wire, you may have fried it.
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Unread 06-07-2011, 08:02 PM   #6
risgate1
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thanks a ton ben, will check that out tomorrow.

as far as the coil, if i dont have power there with the key at the on position, would it be the coil being bad even though it runs when the starter is engaged? what do you mean by the resistor wire being fried?

i ahve the electrical components for an 85 cj with the 4.2 but i swapped in a 304 from a 72 cj5 if that matters in any way.

any way i could bypass any of these issues to confirm the diagnosis?
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Unread 06-07-2011, 08:11 PM   #7
Alby63
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There is a brownish/red wire spliced into the red wire near the module that goes to the + side of coil that lowers the voltage to the coil. There should be, I'm guessing about 8 or 9 volts at the coil with the key on. You can run a wire from a switched power source and temporarily connect it to the coil+ to see if it will stay running.
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Unread 06-07-2011, 08:16 PM   #8
risgate1
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that was on of the wires that was totally fried. i just clipped it and ran a jumper between the now split wire - no idea it was a resistor wire.

running that jumper to reconnect those wires didnt make it run, but i also didnt go very far down the wire either to reconnect them. is this the right way to reconnect them?
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Unread 06-07-2011, 08:18 PM   #9
Alby63
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If there is no power at the coil, remove the two wire plug at the module and check for power at the red wire on the harness side. If there is power there, and no power at the coil, the resistor wire is bad. No power at both means the problem is at the ignition switch or ignition switch wires.
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Unread 06-07-2011, 08:22 PM   #10
Alby63
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Quote:
Originally Posted by risgate1 View Post
that was on of the wires that was totally fried. i just clipped it and ran a jumper between the now split wire - no idea it was a resistor wire.

running that jumper to reconnect those wires didnt make it run, but i also didnt go very far down the wire either to reconnect them. is this the right way to reconnect them?
The whole resistor wire will need to be replaced.
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Unread 06-07-2011, 08:28 PM   #11
risgate1
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alby

thanks a TON

will give that a shot tomorrow - hopefully that gets me back on the road
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Unread 06-07-2011, 08:29 PM   #12
Alby63
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Good luck
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Unread 06-07-2011, 09:37 PM   #13
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Quote:
Originally Posted by risgate1 View Post
i am at my wits end. i was freshening up my 85 CJ (with a swapped in 304), getting her ready for the summer. I took off the front end and shot the engine bay with paint, and put in a bunch of new parts.

I started her up, she ran like a top, took her outside and all of a sudden she died. i will turn the key, she fires for a second, then quits. I looked and saw some fried wires at the starter solenoid - evidently it wasnt grounded good enough. So, i changed out the solenoid and grounded it to the battery, that didnt work, same result. Then i changed out the alternator thinking i fried it, but that didnt work either. I am assuming at this point it is a fantom ground that got fried. Does anyone know where i should be looking at this point from a wire and ground standpoint?

i figure it has to be an issue prior to the ignition coil because if i keep the starter engaged the engine runs until i turn off the key (bad for the starter i know).

any suggestions please! thanks in advance
The dead give away here is when you let off the key, the engine dies...

Alby63 is VERY close on what he told you!

The Jeep/Motorcraft ignition system has TWO CIRCUITS,
One is for 'Cranking' for faster starts,
One is for 'Run' position on the key switch.
There is a resistor in that 'Run' circuit to keep the module alive longer.
(Hold over from the old breaker point days that really didn't need to be there)

Your 'Cranking' or 'Start' circuit is working, the engine fires and runs in the 'Start' position.

It's the 'Run' position/circuit that is suspect...

-------------------------------------

What you need to do is break out the old TEST LIGHT,
The bulb kind you get for $6 at the parts store,
NOT THE VOLT METER!

The volt meter won't tell you if the resistor wire is intact or not, the load of the bulb in a test light will give you better information.

Pop the coil connector off the coil.

Test the terminal in the coil connector, Probe the 'Red' wire terminal.

You should have a 'BRIGHT' light when cranking,
You should have a 'DIM' light when the key switch is in the 'Run' position.

If you DO NOT have a 'Dim' light (Resistor making the bulb a little dimmer),
Then you have found out the issue is between the coil and the cab,
That eliminates the distributor, coil, module and wiring in between saving you a BUNCH OF TIME and harness unwrapping.

Start by checking the 'IGN' fuse in the fuse block.
The next suspect would be the ignition switch it's self,
Check that by unplugging the two wire connector at the module and checking the larger of the two wires for voltage on the HARNESS SIDE of the connector.

If you have voltage there, it's probably the resistor wire or one of it's connectors. Time to start unwrapping harness...
(Always a FUN job... )

---------------------

If you DO HAVE a 'Dim' light with the key switch in the 'Run' position,
Then you probably have a dead module 'Run' circuit.

The way to test that is to connect your test light to the battery POSITIVE and PROBE THE GREEN WIRE CONNECTOR IN THE COIL CONNECTOR.
When you probe, you should get a constant 'Bright' light.

Crank the engine and see if the test light flashes.

No flash, no module switching = Dead Module.

No constant 'Bright' light, no ground to the module.
Module grounds through the 'Black' wire in the module 4 wire connector to the distributor 'Black' wire.

Usually, I run a dedicated ground wire to the module 'Black' wire just to make sure the module ALWAYS has a 'Ground'.

---------------------------------------

These systems are pretty easy to diagnose since they are pretty simple...

Components are,

Distributor, produces signal in the bottom so the module knows when to fire,

Ignition Coil, charges from the power feed from the key switch, then fires when the ground leg of the circuit is opened by the module,

Module is simply a switch, when signaled by the distributor trigger, it opens the coil 'Ground' leg of the coil circuit.

Power comes through the ignition switch, through the fire wall, then splits three directions,
One to the module, full 12 volts,
One to the ignition coil, through a resistor wire,
One to the alternator to 'Excite' charging.

If you have power to the module leg, then you should have power to the coil leg.
If you don't, it's probably the resistor causing problems.

If you have power at both legs (module 'Red' wire, harness side & Coil 'Red' wire connector side) then it's probably not the ignition switch, fuse, ect...
It's usually the module when you have that situation of power in both places.

The joker in the deck is the 'Start' or 'Cranking' circuit.
There is a wire on the starter relay ('Solenoid'), small red wire on the side terminal, should be there by it's self...

This wire supplies a full 12 volts to the coil during cranking.
The extra voltage is supplied there to aid getting the engine started (more current into the coil means more spark energy to get things started when cold)...

Yours is working since the engine starts, and you are running on that power as long as the key switch is in the 'Start' position...

If your engine computer (Emissions) has given up, you may not get you up and running, but this will let you know what is going on.

Diagrams,




Does this help you track down the problem?
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Unread 06-07-2011, 10:03 PM   #14
BagusJeep
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JH, thanks for the data, wish I had it at the weekend when Bagusjeep was dead in the water. Turned out to be a corroded connector at the ICM giving the appearance of a failed ICM. Your test procedure would have nailed it much more quickly than the hit or miss I undertook.
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Unread 06-07-2011, 10:20 PM   #15
JeepHammer
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That's how you learn...
It's not a problem until you encounter it...
Then most times, you don't have the information at that very time, but since it's been an 'Issue' you are watching for answers.

Since this very same 'Issue' pops up so many times on so many forums,
I developed the test light procedure.
$6 test light and someone on the key switch and you are back in business very quickly.

Most guys don't own a good volt meter, and most don't know how to use it for testing resistance in the coil circuit, but the light makes it easy.

Besides, I use a dash light socket on the trail when I don't have my test light with me... Sneaky, but effective!

And the reason I have such detailed information about what CAN go wrong with a Jeep/Motorcraft ignition is because I've had about all of the above at one time or another!
Nothing like having a 50 year old AMC Mechanic hanging around when you need him!
I might be a broken down crusty old fart, but I can still type!

Besides, it's not 'Trade Secrets' anymore, I don't own a shop and there aren't enough '70s AMC around if I did!
Might as well share what I've learned or it's good for nothing now!
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