battery drain from glow plugs and while running

[GentleGiant]

Hello friends,

My '84 M1008 has problem with the front battery draining down very fast.


BATTERY:

I had this same battery problem in the Spring, and let the truck sit in the barn over the summer. Today, it started right up. There is no battery drain while it sits.

While the truck is running, the voltage across the terminals on the front battery is just over 11 volts. Not good. Should be more like 14. The back battery is about 14.

The battery itself is old, for sure. But when I charge it up to 13 volts and then put a load tester on it, I get the coils in the tester nice and glowing orange, like a toaster, and the battery is only down to 12.5 volts after that. The tester never shows "bad" with its needle... always in the "good" or just barely into the "weak" range.

GLOW PLUGS:
I replaced the glow plugs last year and that solved the starting problem I was having. (Many thanks to this forum). Could this have caused a battery drain problem? Maybe I need to replace the relay or solenoid? This truck has not had the recommended bypass modification done.

It seems that the glow plugs drain the battery very fast. I charged up the battery to 13 volts. Running four glow plug cycles on a cold engine brings it down to 8 volts. It won't even turn over properly after that.


ALTERNATOR:
I thought it might be the alternator. When the key is turned on, the Gen 2 light comes on, but the Gen 1 light does not. I read on the following thread that if the dash light is not on, the alternator will not work. But it was for the Gen 2 alternator and light

http://www.steelsoldiers.com/showthread.php?54292-CUCV-alternator-symptoms-diagnosis-and-fix

Last Spring when I used the truck, it would start fine with a charged battery, and then I could use it and stop and start it a few times, before the battery had to be charged. I noticed that if I drove a long time, the battery would be dead, without having used it to start the engine more than just the one time. That's why I suspected the alternator at first.

However, the battery gets drained badly by just running the glow plug circuit a few times without starting the truck at all, and the alternator is not involved in that at all.


WHAT DO YOU THINK?

Thanks!
Eric

 

[MakersTeleMark]

Have you tried swapping batteries?

 

[Warthog]

Both light for both alternators have to work for the charging systems to work properly.

While running all the electrical needs are from the front battery only. Injector pump, lights, etc.

Fix the GEN1 problem and see what happens.

First thing to check is the heater fuse. It controls the GEN1 exciter circuit.

 

[Tow4]

If the gen light does not come on when the ignition switch is on before you start the engine, that alternator will not work. The gen light is what turns on the regulator once the engine is running.

I drove my M1028A2 halfway to and all the way back from the GA Rally with the number 1 alternator disconnected because it started over charging. I charged the front battery over night and drove all day starting the truck several times.

Check the glow plug side of the glow plug relay to see if the glow plugs are on. If your front battery goes dead quickly while the engine is running even with the #1 alternator not working there is another problem.