ecgleaton

Hey y'all,

I have a stick shift 93 cherokee that keeps blowing the "engine control 2" fuse. It starts and runs fine, when I try to back it up the hill it's parked on the fuse blows.

I can start the Jeep, rev the engine, rock it up and down, back and forth, even coast up and down a hill, but when I start to drive in it immediately blows.

The only things running off this fuse are the coil and the fuel injectors.

I've already tried:
-a new coil
-another computer
-unscrewed the large charging wire from the alternator
-looked over all wiring, no obvious grounding out to the body
-tested the "auto shutdown" relay the fuse runs through and the relay connections

Tomorrow I will unplug the rest of the wires from the alternator, I may replace the distributor button and cap, but other than that I will have to follow all the wires.

Is there anything else I can do, or has anyone else had this same problem of only blowing the fuse when it starts to move? Would appreciate any advice! Thank you!

freegdr

Automatic ?

jakemac2009

I had the same issue a few months ago and mine ended up being an alternator

ecgleaton

Free, It's a stick shift.

Jake, did you end up having to replace the alternator? I think one of the smaller hot wires coming off the alt could be grounding out, because the bolts they screw onto are very close to an engine mount. I can't figure that out, it looks like I won't even be able to get the wires off without removing the alternator.

jakemac2009

The alternator was bad it had a bust bearing in it and after that everything worked fine so all I'm saying it's the alt can be shooting some extra juice cause the fuse to blow

ecgleaton

UPDATE: Problem solved!!

It did end up being one of the smaller wires coming into the alternator. The voltage regulator inside the computer ended up going out simultaneously, and rather than replace the computer for $200 (I have a 4-cylinder, and I could not find a working computer for my Jeep at a junkyard, 6-cylinder computers will not run mine), I ended up buying an old-school Chrystler external voltage regulator and wiring it up, and the system is charging normally now! I will post a detailed write up of this mod in a few days complete with pictures, and post the link to the new post here.

Thanks for y'alls input, I appreciate it!

ecgleaton

Hey y'all,

I just want to revisit this post with what ended up being my true final solution. The old school Chrystler voltage regulator never really worked that well, the voltage always swung wide from 10 to 18 volts or so, especially at idle. I would rev the engine and it would usually go away though. Not sure if this was due to a junkyard alternator, though I've tried this setup with a new alternator with the same result. Still, something else in my setup, my wiring or the old alternator could have contributed to poor results and early demise of this setup.

I last posted in December '14. Now, August '15, I have finally found what appears to be a permanent fix. Eventually the Jeep had to be parked since late April when I couldn't get the voltage to hold steady no matter what.

I went to an auto electrician, referred to me by a local service shop (this may be a good route to finding a good specialist auto electrician), who got me a new, stock model alternator, and a custom voltage regulator which he installed inside. This VR is made for this alternator, so it fit right in. I'm happy that this is not some jerry-rig, everything is designed to work together. The voltage holds steady now, and I had Advanced Auto test the charging system, with everything coming out good.

I couldn't find the documentation when I looked for it just now, but if anyone ever runs into a similar problem and cannot find this part, just post here and I will call up the guy and get the part number. It really was a life-saver, because no one had ever mentioned this possibility before. I essentially created a "one-wire" alternator, without having to do any sort of custom bracket fabrication to put a GM alternator on there, which I have only heard bad things about. This way the electrical problem was solved electronically and didn't spread into a mechanical problem as well. I also avoided having to buy a $400 rebuilt PCM (I have a 4-cyl and it's difficult to find them in a junkyard). All in all, the alternator, custom internal voltage regulator, and labor to have it installed into the alternator was $200 cash (I installed the alternator into the Jeep). Not a bad deal! Hope this helps someone else!

For the record, the Chrystler voltage regulator was around $40 or so. If you are in a pinch maybe it will work for a few months like mine did, though I highly recommend this new setup as soon as you can get it. Fixing voltage swings was worth the money.

ecgleaton

One more follow up.

The other day I was coasting to a stop and my Jeep suddenly cut out and would not crank. I narrowed it down to a no-spark condition. Messed around with some underhood fuses and I heard a clicking in the cruise control servomotor as I did. I unplugged this, and was able to start the Jeep and move it to a parking lot. I was getting all sorts of strange error codes from the CEL. I reset the PCM and continue driving without issue.

Later in the day, I was leaving a parking lot and the same thing happened. Again narrowed it down to a no-spark condition. Using a DVM, I saw the voltage going to the coil was at 3.6V. I unplugged every single fuse until only two were left. If I pulled either, the voltage held for a second, then dropped to 0V. Looking at wiring diagrams, I was able to determine that both fuses went to the PCM, one to the key switch supplying the "on" signal to the PCM, and the other to actually power the PCM. The voltage remaining for a second also gave me a good indication the problem was in the PCM.

The ignition coil is on the same circuit as the + side of the alternator field circuit, and this circuit also leads to PCM pin # 57, labelled as "sensor feed" or something similar on the wiring diagram. I researched this pin and couldn't find any information saying it was essential. I cut the wire near the PCM, and voila, my Jeep ran again.

Let me sum that up. Two wires run from the PCM's integral voltage regulator to the alternator field circuit to charge properly. If you go the route I previously described, installing an internal voltage regulator in the alternator itself, it may be a good idea to go ahead and cut both wires leading to the alternator field circuit near the PCM. Haven't had a problem since. Apparently another short in the integral VR caused my stall-out, no-start condition.

EDIT: Also, the battery indicator light does not light on the dash, and the alternator field circuit error code #41 only comes up sporadically. Not bad!

ecgleaton

Just found the work order. The internal voltage regulator part number is 230-52049.

http://www.finditparts.com/products/...nd-n-230-52049