CJ7 runs for a while then starts jerking, won't stay running

About 3 years ago, I bought a 1980 CJ7 Renegade. Had about 47k original. I believe this because of no rust and good running condition. For the past YEAR I have been trying to get it running right again. Here's the deal. She will crank and purr like a Singer sewing machine. She may run perfectly for 5 minutes or an hour, but at some point she starts jerkiing like she's starving for gas. We have replaced everything (including new carb, tho that's not the problem it turns out). Have changed fuel pump, using gravity and electric, dist. cap, lines, checked tank and other stuff I can't remember. Looking for suggestions. Any appreciated. by the way, 283 six cyl. 4 speed manual

 

Hello Jack, welcome from Oklahoma.
Do you mean a 258 six cylinder?
If you shut it off and restart it does it run good again or do you have to wait awhile?

 

two quick thoughts-
1) An exhaust restriction. Loosen exhaust, if an o2 sensor engine remove sensor to vent exhaust.
2) FUEL vent valve plugged. ie wrong cap - misrouted lines. Run with cap open or OFF CAREFULLY.

 

It sounds more electronic than fuel. Is 1980 the first year for the computer control? To get the jeep running perfect I would perform a nutter-bypass and install an HEI distributor. This will remove all of the Ford electronics that are causing your problem including the computer, ignition control module (ICM), coil, and distributor. If no computer this will be a little easier. That ICM gives fits when it starts going bad. You can likely get an HEI distributor on ebay for less than $100 that will bolt into your jeep. Also check Quadratec, Morris 4x4, and 4wheelparts for price comparison.

 

no, it won't immediately start but you can wait, sometimes an hour or overnight, and it will crank and run fine. There is no predictability on that either, however; and yes, it is a 258

 

ok, I do not know if 1980 was the first year, but it does have the little computer "box" on the wheel well, driver side, which we replaced. Are your saying search for the HEI and install it and that's it? Or, is there something that has to be removed also (I aint a mechanic)

 

I have slept since my first reply and can't remember where I may have been going with it except that I thought it might be heat related.
Heat and electronics don't mix, especially failing electronics. A wire with a bad connection, heat causes resistance and with heat expansion the metal can actually move causing no connection.

 

After a little research the 82-86 CJs have computers. That box on the wheel well is the "Ford" Electronics control module (ECM) not a computer. If you replace the coil and distributor with a HEI set up, you can then remove the ECM. Take the thick power wire (red/white stripe) that feeds the ECM and extend it and use it to feed power to the new HEI distributor. The new distributor will have another plug left open. That is to feed signal to a tachometer if you want one or already have one.

 

Did this issue ever get resolved? It does sound like it could be the ignition control module as OFFGRID suggested.

 

One more thought is that the elctronics in the distributor are going bad. Mine started doing this and I first replaced the ICM. did not fix it, but next I did the HEI distributor swap and fixed the problem so I believe it was the OEM distributor that was going out. HOpe you get it fixed.