Electrical Nightmare!!!

[edolch]

So here's the story. I have an '81 CJ7 with the 4.0 and 3 speed. It's great fun. The previous owner left a wiring nightmare like nothing else. Very shortly after purchasing it (before I had time to really dig into the wiring), the entire wiring harness burned up. My friend and I got a wiring harness from a doner CJ7 that was just slightly newer (mine had glass fuses, this has plastic). I've got it all in and the Jeep is back together. Every gauge, switch, and light works. When I go to start it it gets plenty of fire, but it won't run. I've also replaced the starter solenoid. What in the hell is keeping my CJ from running?! I'm no mechanic by any means (though the friend helping me is) and I hate electrical. Got any ideas?

 

[808CJ7]

Check that your distributor and coil have power when the key is on. It might have spark while your cranking it but looses power when you release the key

 

[69jeepcj]

Oh what a mess. Reminds me of mine when I got it, lol. You say it gets plenty of power when you go to start it. How do you know?? Are you checking for volts with a meter? Does it crank over or just click when you turn the key? You say it wont run, is it starting and just won;t stay running. MORE DETAIL please.
As 808 said check for power with key turned and not turned. Check for power everywhere, ignition switch, coil, dist, control module. blown inline fuses. The control module is one of the first things I look at with a no start situation on the 6cyl cjs. Usually turns out to be the problem, they are junk. If that is what it turns out to be I would buy a spare and keep it with you as they can go out with no warning.

 

[edolch]

I haven't checked anything since I posted this thread (been working late). Anyway, it cracks, it has spark, and it seems like it turns over and immediately dies.

 

[Utah_jeepster]

I haven't checked anything since I posted this thread (been working late). Anyway, it cracks, it has spark, and it seems like it turns over and immediately dies.

Try this simple trick pour a little gas into the carb and see if it will sustain a short run. You might be chasing two diffrent problems here. Does it have a eletric fuel pump?

 

[69jeepcj]

If your sure your getting spark, then its not the module. I would do as suggested above and see if it runs then. 3 things are needed to run an engine, air, fuel, and spark.

 

[TLCJ5]

Does your Jeep have a ballast resistor? The ballast resistor is bypassed in the start position so that the engine gets a hotter spark to start. When the key is released& switches to the run position the ballast resistor is in the ckt. If the "newer CJ" didn't have a ballast resister & yours does you may be missing that part of the ckt. If the engine dies as soon as you release the key check for voltage at the distributor in the run position.(as 808CJ7 & 69jeepcj suggested). GOOD LUCK & keep us posted as to what you find!!!!!

 

[69jeepcj]

I was thinking about this and thought if while messing with the wireing could you have pulled off a vac hose somewhere. I know the carb should have a big port for the power brakes (if you have them) and if its off the engine will act as you discribe. Just another thought.

 

[frhrwa]

still, back to that original queston, IS there power at the coil when the key is on... when you start it and let go of that key, the 12v should remain on the coil.. if not, ....... also, you didn't mention what year the 4.0L was, does it or did it have an ECU?