Electrical issues

[College Cummins]

Alright, I've searched about as much as I can, and now I'm posting my own thread. The truck with start and run fine, but will only charge when I am sitting completely still. I believe that there is an intermittent ground somewhere, but I can't find it, and my Dad is in MO with my FSM, so I can't track down all the grounds to check them. I checked my ground under the dash, the one on the core support, and of course my negative ground cable. The lights will pulsate like a disco ball when I am running down the road, but work fine when I am sitting still. I have put an external regulator in and have bypassed the PCM in regards to the alternator, but everything else is run through the PCM. I'm about at my wits end chasing wires all over the place.



Any help or insight is greatly appreciated.



Thanks,



James



Ps truck won't shut off with the ignition switch either, I have to pull the pump wire shut her down

 

[pepecat]

What about the ground going from the Neg Batt Cable to the front clip. If you for instance touch a wrench to the hot lead to the fender, this ground will heat up and go bad - too much resistance. Just clean the contacts if so.

 

[p-Bar]

I would check for ground strap engine to frame try just using one side of a jumper cable

 

[JLEONARD]

just using one side of a jumper cable

Yes try using a temporary ground. . jumper cables will work for an experiment.

If it solves the problem install an additional permanent ground and be done.

 

[College Cummins]

Thanks guys, I'll triple check that (I've already checked the battery ground previously, twice, lol), and try to bypass my original ground with a jumper cable to see if that does it.



Thanks

 

[College Cummins]

alright, that's a no go on bypassing the original ground wire. I had the truck running and tried to jiggle the wiring harness and the ground wire and main harness as if I was running down the road, but couldn't get the truck to act up. It just stayed charging and the lights didn't flicker or anything. I just can't think of why when I'm sitting still, whether I'm in gear or in park or in neutral, it will charge, but not when I'm moving. I was thinking it might be a sensor not registering the speed of the motor, but I can rev it up in park or neutral and it still will charge, it does put a slight draw on the amp gauge, but the lights and all work fine.

 

[p-Bar]

what are you using a an amp gauge? the stock? or an aftermarket? If it is the stock gauge I would use a digital volt meter and monitor it that way

 

[College Cummins]

I am just using the stock gauge, however the charging issues are tied to the lights, radio, wipers, and pretty much all the other accessories that work when the truck is stopped, but act like there is a short/intermittent ground when moving.



Thanks,



James

 

[p-Bar]

Maybe it's more a short rather than a charging issue. I think the volt meter would tell you that. Try a volt meter and pull all the fuses that are not needed to drive the truck and start one by one reinstalling them after some drive time. But you must monitor it with a volt meter, digital is bst as I stated before. Wish you were closer I'd come over and help you with it.

 

[BGore]

Just one other thought - make sure your intake and fuel heater systems aren't kicking on for some reason when you're driving. You can disconnect them temporarily to eliminate them as a source of trouble.

You can get an inexpensive digital volt meter that plugs into the cigarette lighter socket at various auto parts stores, Wal-Mart, or from online sources like JC Whitney. Usually they are around $10 or $15.

I use mine when I'm plowing, since the plow puts quite a load on the electrical system.

Maybe this will help you figure out what's going on. Many of them have red, yellow and green LEDs that you can see change while you drive. Mine is almost always reads between 13. 8 and 14. 0 volts unless I've started it cold and the heaters are running, or I'm lifting or swinging the plow. It's a good, inexpensive way to get a "second opinion" on what's happening with your electrical system.

 

[College Cummins]

Thanks guys, both of those are great ideas that I'll try ASAP and get back with the results. I do agree that it sounds more like a short than an actual charging issue, that just seems to be how it presents. I wish you were closer too, I could use some hands on advice on the truck, lol



Thanks,



James

 

[Moe]

My 92 did the same thing. I found that the crank sensor had slipped and was intermittently touching the harmonic balancer. Put on a new one and that cured the problem. Whenever the sensor would scrape the balancer it would quit charging but the engine would keep running fine. Good Luck. MOE

 

[College Cummins]

Alright guys, I'll know more tom, but I went to put a new crank sensor on after trying the other two ideas, and i took the battery out to have it tested, just off of a hunch, and it's tests out bad. Now what I'm thinking is that there is a broken plate or something like that in the battery. It is one of those maintanence free batteries and now that I think about it, when I turned to the right, the truck no longer acted up, it charged and the headlights were fine and all, so, maybe that plate stood up right, or maybe it was covered with the sulfuric acid, or i don't know what else, but I'm gonna get a new battery tom, and hopefully that solves the problem and I'll have to sell that crank sensor I bought, or I'll have to hang onto it for when it goes, out, lol



James

 

[Moe]

Letus know what u find out. This is interesting. MOE

 

[p-Bar]

Interesting thing with the battery. Hang on to that crank sensor never know when you will need it.

 

[College Cummins]

wasn't the battery. the battery was apparently bad, but that wasn't the cause of the trouble. Time to replace the crank sensor.



James

 

[91.5oneowner]

Do only the automatic equipped trucks have a crank sensor?



If not what is it "sensing"?



Never noticed one on my truck, only sensor is for the tach.

 

[PToombs]

89 to 91. 5 trucks don't have them. When they went to I/C they added a PCM, Crank Sensor, and a bunch of other goodies. The sensor controls A/C, OD, charging, and cruise control. I think I missed something? Ah, well, you get the idea.

 

[91.5oneowner]

Huh, where's it located at.

Mine's a '91. 5 and has a "computer" in the fender behind the battery (and intercooler) but I've never been sure of what exactly it controlls.



So the '89-'91s don't have it?

 

[Moe]

My 92 had the sensor located on the front of the engine looking down at the balancer which had a mark on it. If the sensor didnt "see" the crank turning then it will not charge. Check to see if you have a wire running straight down behind the pulley. On the end of the wire it should have a sensor aimed at the crank. If it does then you need to make sure that it has the correct gap from the balancer. On my 92 I set the gap with a brass feeler gauge as the sensor is a magnetic pickup. I guess I really dont know if your 91. 5 has the crank sensor in that location, but its worth a check, MOE