84 CJ no spark from coil

[Techlight]

Hey All,

Need a bit of help...

Jeep wont start...no spark from coil.

I was driving down the road and jeep just quit like it ran out of fuel. Towed it back and started looking for electrical issues.

I've checked all fuses including the howell TBI fuses and main stock fuses...checked solenoid power, distributor pick up coil, and changed ignition control module (cause i had an extra)...i also changed the coil out because I had an extra and same problem...anyone want to chime in on next steps? I have no spark from coil and I'm lost at this point. Anyone want to walk me through the basics that I might have missed and the rest would be greatly appreciated...we're moving into top off weather here in SoCal and I'd like to be cruising that way hunting for snakes haha.

Thanks in advance.

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[gert]

Do you have 12 volts to the coil? Do you have a ballast resistor? Do a ohms check across the ballast resistor if you have one. Also there is an ohms check for the coils it wouldnt hurt to perform that as well


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[Posi]

If you have the stock distributor you should have 6v at the coil with key on.
Post up your readings

 

[gert]

If you have the stock distributor you should have 6v at the coil with key on.

Post up your readings

Hey posi
Why 6? My understanding is the ballast resistor is only used during cranking


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[Posi]

Anyone want to answer this before I do?

I'm willing to bet gert will figure it out before someone answers.

 

[gert]

Anyone want to answer this before I do?

I'm willing to bet gert will figure it out before someone answers.

Grrrr son of a donkey lol makes sense full voltage at start and drop voltage while running


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[Posi]

Yes sir

 

[Posi]

If you have the stock distributor you should have 6v at the coil with key on.
Post up your readings

If he finds 6v the next test would be to check the voltage at the coil with the key in the start position. Should have 12v

 

[Lumpy Grits]

Run a 'jumper' wire from the POS(+)side of the battery to the POS(+)of the coil.
Will it start now?
If it does-Don't run it much more than 5 minutes, as the coil is get'n full voltage.
LG

 

[mtnwhlr]

Are you still running the stock horse shoe clip to the coil? A common problem I had to change mine out on my '84 because it would just die out of the blue.

 

[mtnwhlr]

Here's what I did

 

[Techlight]

Hey All. Thanks for the responses.

I'm not sure about the ballast resistor. Where would I find that and does anyone know what its resistance should be?

I have 6v to the coil in the on position not 12v.

It is the stock dist. When I unplug the dist and check the resistance on the pick up coil it's reading .649.

I tried the jumper to the coil and still no start.

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[Posi]

If he finds 6v the next test would be to check the voltage at the coil with the key in the start position. Should have 12v

^^^

 

[Techlight]

I did check the horseshoe clip and it seems snug. I recently put a new one on a few years ago but I'll see if I can hunt one down just to eliminate it.

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[Techlight]

It's not 12 in the start position. It's more like 8-9 v

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[Posi]

You have a short, or open, in the wire that goes to the ignition post (I) of the start solenoid and coil. Sometimes it’s a poor splice connection between the 2 wires going to + side of the coil.

Edit: I’m not suggesting that’s your only problem however, you have a voltage drop that needs to be corrected. You need battery voltage in the start position. Having 8v-9v I would first look at the splice and connection to the I post.

 

[Posi]

I'm not sure about the ballast resistor. Where would I find that and does anyone know what its resistance should be?

Engine side of the dash connector (brown wire) sliced with the ignition wire that runs to the coil. 1.35 ohms.

 

[Torxhead]

Techlight, pick up coil should be 400-800 ohms so you are good to go there. Just to clarify, you have no ballast resistor. You should have 6v at the coil and icm. Like Posi stated, you should be getting full battery voltage during startup. There is a red with white tracer wire from the starter relay to the coil that provides it. When the engine is running, a resistance wire from the alternator #1 terminal to that red w/white tracer wire that takes over voltage to the coil. Its always nice to have a CJ wiring diagram handy.

 

[Posi]

Just to clarify, the ignition wire with the resistor that runs from the ignition switch to the coil is working as it should hence 6v key on

Your voltage drop is in the starting circuit. An easy way to test the wire that runs from the I post to the splice at the ignition wire is to crank the engine and probe the I post, then probe just the wire in question at the post. If you read battery voltage on both the drop should be at the splice or the wire. If the I post does not ha e battery voltage the drop is elsewhere in the starter circuit and you will need to preform a full voltage drop test on the starting circuit.

You did confirm fuel spraying from the injectors while cranking?
Battery should be at full voltage (12.6v) for all tests.

Besides the voltage drop you may have another issue going on.

 

[Lumpy Grits]

There's a OEM resistor wire in the wiring loom on the firewall, on the P'side kinda near the battery.
Try a new coil-MDS with ring terminals.
Is this the CJ with the FI mod?
If so-Ck your CPS for function.
LG