For years, this has been the main way the CJ ignition switch has been wired.

There have been additional items added such as the computer But this is the basic.

The "IGN" wire sent power THROUGH the tach, if equiped, then to the Duraspark ICM and then through a resistor wire to the (+) on the ignition coil.

This is for a 84 CJ but close enough to a 79 to make sense:

 

Thank you. This helps immensely. I have a huge mental block when it comes to understanding more than a simple switched circuit. And reading a schematic is like reading ancient hieroglyphs. And this is the easy stuff!

My next challenge is figuring out why the brake and backup lights aren't working. And I've given up on the fuel gauge ever working.

 

Brake lights are a little more challenging, they go through the turn signal switch so they have to be connected and working.

The backup lights follow a long path to the tranny switch but an easy one.

 

The "IGN" wire sent power THROUGH the tach, if equiped, then to the Duraspark ICM and then through a resistor wire to the (+) on the ignition coil.

Would this be the ballast resistor that is on the firewall? Wired as above, but still not cranking. For some reason, the "IGN" wire is wired into the fuel gauge. However, the starter switch was working before...

 

In an OEM setup it's a resistance wire. Some people replace that wire with a ballast resistor. You should never use both. It will drop your voltage too low and will not start.

 

Got the ignition switch working today. Brake lights are another story everything is connected. Should be working. Not sure why they aren't. They were before. Electrical gremlins will be the death of me. Give me 120v AC any day!

 

Need to get a test light. And you can find were the power stops.

Do the 4-way flashers work?
Do the turn Signal works?

 

Managed to get nearly all the electrical gremlins evicted. For now at least. Only thing I'm fighting currently is that all my dash lights are staying on. All the time. Could be worse problems. At least the safety lights function. Stop, turn, tail.

 

You probably have an orange wire crossed with a red or red with tracer. Jeep wiring is quite simple if you keep the colours in order and don't mix them together(POs don't)

The orange wires are powered by the ACC LPS fuse. You can pull this fuse and then see where the wires are spliced with something else or disconnect them one by one from the panel instruments until they go out. Then check you have voltage at he fuse holder and put the fuse back in.

It is worth checking your light switch is not feeding voltage all the time to that circuit. It comes from a seperate tab on the side of the switch that feeds back down to the fuse box LPS ACC fuse and then out through the orange wires.

 

Well, I'm back with this thread........

I have the ignition switch starting and running the engine. Problem is when I return the key switch to off, the engine doesn't die. Just keeps running. My volt gauge was crapped out so upon replacing it, I can see what is happening. The switch is turning off the power, at least it is showing it at the gauge. However, the engine still runs. I am able to kill it by turning off the electric fuel pump.

Remember, this is a 79 CJ7 with a junkyard MPFI. I'm thinking somewhere in the process there is a wire that is crossed or something not right to cause it to not turn off. Any ideas from the great minds as to why it doesn't turn off. Or circuits to check...troubleshoot...etc.

Thanks!

 

Well, I'm back with this thread........

I have the ignition switch starting and running the engine. Problem is when I return the key switch to off, the engine doesn't die. Just keeps running. My volt gauge was crapped out so upon replacing it, I can see what is happening. The switch is turning off the power, at least it is showing it at the gauge. However, the engine still runs. I am able to kill it by turning off the electric fuel pump.

Remember, this is a 79 CJ7 with a junkyard MPFI. I'm thinking somewhere in the process there is a wire that is crossed or something not right to cause it to not turn off. Any ideas from the great minds as to why it doesn't turn off. Or circuits to check...troubleshoot...etc.

Thanks!

How are you 'turning off' you electric fuel pump? Is it on a switch by itself or is it on a relay controlled by the PCM? If on a constant hot switch by itself and using the PCM for ground without a relay, you might be feeding power into the system that way.

 

It sounds like your ALT sense wire go tied into the power for the computer. When you turn the jeep off, unplug the brown wire off of the alt and see if it shuts off or not.

 

Brown wire isn't even connected. Not sure where it goes.

 

What wires do you have on the back of the alternator? Have you converted to a one wire setup?

 

Alternator to battery wire, connected at post on back of alternator, then pigtail from that post to plug on top, post nearest passenger fender. The brown wire put into space. Feel like it belongs somewhere, just don't know where at

 

You need to put a diode on the alternator sense wire. It's back feeding and keeping the motor running


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http://www.thecj2apage.com/forums/delco-3wire-alternator-help_topic34231.html

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Diode on the dense wire has been mentioned several times and one is on its way. However, i would think that the engine would die when that wire is unplugged?? It does not.

 

If it's not killing it when you pull that wire then you have something else going on. Turn it off and check your pin out on your ecm. Any chance you miss wired your 12 volt constant and switched?


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It is entirely possible. Just wanted to go through the obvious and easy options before digging into the ignition switch and wiring. I'm too fat to be upside down under the dash!

 

Aggie jon...you in college station? Lol

Need to check on why the ignition coil is still getting power... What connections you have on your starter solenoid? My guess is the "I" side has another hot connection on it back feeding

 

That's a real possibility I didn't even consider that. Check the voltage at the solenoid


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I'll check the solenoid wire. I also took my ignition switch off to look at that.

Here is what I have. Not sure who is who.

 

Checked the voltage on the solenoid on the "I" post. 9v when key in run position, 2.6-3.4 when key in off position, engine continuing to run.

Straight wire from solenoid into the bottom of the PCM that I use for my MPFI swap. I wonder if a diode would help remedy the issue? And if so, what size diode?

 

Checked the voltage on the solenoid on the "I" post. 9v when key in run position, 2.6-3.4 when key in off position, engine continuing to run. Straight wire from solenoid into the bottom of the PCM that I use for my MPFI swap. I wonder if a diode would help remedy the issue? And if so, what size diode?

tested the "I" wire on solenoid. Removed it while running and with key in off position and it continues to run. Aargh! Like chasing a rabbit. So to summarize...plug at top of alternator disconnected. Solenoid wire disconnected. Ignition switch in off position. Continues to run.

The two battery wires into the ignition switch, is one hot constant and one switched, or both constant hot?

 

Remove the power from battery and it dies? If not name her Christine and call a priest...

Ignition is off you should not have power to the "I" side. From that terminal forward to the engine is spark which if you could stop that it would not run. So where is the power coming from? 2 possibilities come to my mind..

1 is its back feeding and downstream from the "I" terminal there is something bleeding power into the circuit. This circuit used to go to the + terminal on the ignition coil before it went FI, now I assume it goes to a coil pack?...

2 is your starter solenoid has broken down and is bleeding power internally from the constant power from the battery to the "I" terminal....time for a new solenoid.

One check to confirm which route to go is to remove the "I" terminal from the solenoid while ignition is off but it's running- if it continues to run the power is coming downstream(option 1 above)..if it dies then option 2 (new solenoid). I think you did this test already but I cannot go back and look. From there you get to find out what else downstream is causing the voltage to "back feed" that line.

Make sense? I'm doing this all from memory so don't be afraid to question something!

 

Ok also diode- not the problem. You did the test already so look downstream for what has power going into pcm🤔... Circuit boards can bleed power if they get damaged by heat or dirt/rust. So pcm could be doing it internally or else there could be a splice that's not necessary...

 

pcmedd14...???...

Where is pcmedd14?