Engine wont shut off and random battery drain. Help!

[grampsbutler]

I am new to Chevys, and have an issue which has me stumped.

I have a 84 Suburban K10 with 6.2L diesel V8. I have owned it for about 3 years, when I first bought it I had a charging problem, so I replaced the alternator and batteries. That fixed the charging issue, but now I have an electrical problem that is getting worse.

Symptoms: 1: The battery is going flat while driving....sometimes very quickly (after a 20 minute drive) I wont be able to restart. I will put it on a charger and batteries hold charge, but will will go flat while driving. I put a volt meter on the battery terminals and I am getting 13.4v running, which indicates that the alternator is charging. 2: The engine wont won't shut off with the ignition key. The dash lights go off, but the engine shutoff solenoid remains energized. I can usually get it to shut down by shifting into gear and then trying again several times.

I suspect the ignition switch is causing the shut off issue, The battery drain issue has me stumped. I have checked the harness for obvious shorts and or burned wires, and cant find anything.

Any suggestions what could be causing this would be greatly appreciated.

 

[SirRobyn0]

I can't help you with diesel specifics, but I maybe able to give you some thoughts on the electrical stuff.

13.4 indicates some voltage. Is that measurement at idle? Voltage is not a guaranty of amperage. Turn the headlights, blower motor on and rev the engine up some, now what's the voltage, it should be higher than 14.0V, if it's at 13.4 or less then it's not charging enough. 13.4 might be enough to maintain the battery but if for some reason that's all the alternator can put into the battery that's not going to keep up with electrical loads on.

Do the other electrical things on the truck work ok? If there are a few things not working consider a possible bad ignition switch.

Hopefully someone that knows these diesels will come along with more specific info than I can provide.

 

[grampsbutler]

Thanks for the reply. I will test it underload today and report back .

 

[fast 99]

On the charging issue. 13.4V is low, depending on the battery state of charge 13.8 to 14.5 would be better. If a digital voltmeter is available check the AC voltage. If it is near .100 [1/10th] VAC running a little above idle further checking of the alternator is justified. There are several factors that effect that number such as state of charge and battery condition. A number near that indicates a possible problem with the rectifier. A bad rectifier can cause a battery drain when parked and low or no amperage output running.

FYI there will always be some AC voltage

 

[rich weyand]

You do have the chassis and cab grounds connected, correct?

There are four items on the vehicle that need to be grounded to each other: the battery, the block, the chassis, and the body. Connecting four items takes three wires.

One wire is the heavy battery wire to the block.

Second wire is the smaller battery wire to the radiator cross member.

Third wire, and the one often removed and left off, is a small copper braid from the passenger-side cylinder head to the firewall.

Check that all of these are 1) present, 2) have clean contacting surfaces.

If any of them is missing or corroded, you can get all kinds of weird behavior. The block and the body are on isolation mounts that are not connected electrically without those wires.

 

[grampsbutler]

Thanks for the replies. I took your suggestions, tested voltage at load, and it was only 12.8. So this week I replaced the alternator and removed and cleaned all my ground connections. Sure enough this solved the problem.