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need help quick, dead truck

3K views 24 replies 7 participants last post by  ArcticDriver 
#1 ·
Hello everyone,

Haven't been on here in a long time (no need, trucks been running great, no problems til now. And its a doozy, so I come here seeking knowledge from the fine members on this site. This is how it began.
First start of the day was ok, but when I started it to leave my workplace, it seemed to turn over just a bit slower. Went cross town to my surgeons (double hernia) office, go to leave, truck barely turns over, starts clicking That's when all the whistles and bells started going off, including the wipers taking one swipe. Called the wife who was just getting out of work to come jump me. Started right up, so I took off for home and about 3/4 of the way there, battery light came on (that was one of the lights flashing the first time), along with all the other dingers and bells. Got home, shut it down, tried to restart it and it just clicked. Let it set a bit, tried to start it again and it was dead. When I say dead, I mean DEAD. There is absolutely no power to anything, headlights, dash lights/gauges, nothing. So this is where I'm at and this is what I've done so far.

1. cleaned up battery post/terminals
2, cleaned up every ground I found
3. replaced solenoid (the one on the p. side inner fender)
4. swapped gem module with known working unit, still dead
5. pulled pcm out just to give it a once over, looking for possible water intrusion. I see absolutely no stains or any indication of water.

So now I'm at a standstill, waiting for a buddy and his son in law, who is suppose to be a wiz with these 7.3's., to come over Friday evening to look at it. And by coming over then, screws me out out sending away for whatever it takes to fix this beast. Oh, he took a stab in the dark thinking it's a wire harness/plug. To me, it sounds like something went haywire in the gem or pcm, we'll see.

A few things you should know, the batteries are a couple of years old and in good shape, all battery cables/terminals are original and in good shape, starter is a couple of years old and in good shape. This truck has never had the dreaded windshield or cab light leak, no wet carpet, ever. That's about all I can think of, let me know what you guys think. Thanks, Mike
 
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#2 ·
Sounds like an internal short in one of the batteries or an alternator problem. Those really are the only possibilities. Pull your batteries and your alternator. When your buddy gets there, have him run you to the parts store for some testing. One of those is your problem.


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#3 ·
First check should have been battery voltages. Those gremlins you describe are typical with low voltage.

As RT said, sounds like alternator.

“Good shape” is tricky with batteries & alternators & starters. The only way to know if they are in good shape is bench testing (load testing).

If your alternator is not charging then the batteries may need replacing. 2-3 years is average for lead-acid.

Good Luck.
 
#4 ·
voltages

Yea, wish I would have checked that. So it could be the alt. or batteries, don't think its the gem or pcm at all? It would be awesome if it was one of the two.



Mike
 
#5 ·
Like RT and Arcticdriver said --Batteries or Alternator.
Your basic toolbox should contain a voltmeter (even a cheap one). If you don't have 12.5 V on your batteries at rest, they're discharged. Since you were able to jump it to get running, I would suspect your alternator hasn't been charging. The battery light doesn't always come on if charging isn't up to snuff.
 
#6 ·
Handy having a voltage gauge on the dash ?
 
#7 ·
Question

Appreciate the quick responses guys but I do have a question. If the alt. is bad and batteries good, wouldn't the lights and everything come on, and the truck start up and run even? Until the batteries are drained? And then it would just die again? Or is my thinking off here. Thanks



Mike
 
#10 · (Edited)
Appreciate the quick responses guys but I do have a question. If the alt. is bad and batteries good, wouldn't the lights and everything come on, and the truck start up and run even? Until the batteries are drained? And then it would just die again? Or is my thinking off here. Thanks

Mike
Yes, that is what is happening. The alternator is not producing peak voltage (around 14.2V) so the batteries are in a chronic weakened state. As the alternator output deteriorates further, the available reserve capacity of the batteries becomes less and less but the alternator might still be producing enough amperage to keep vehicle operating and allowing some voltage to be stored in the batteries...until demand increases or alternator fails further.

Add a change in routine such as rain requiring wipers or night requiring lights or even colder weather requiring longer GP cycle and those weakened batteries lose enough reserve to let the truck operate.

But batteries will regain some voltage after sitting. So the truck may start after it sits but quickly get depleted with GP and starter draw.

There is a minimum voltage required for the PCM to allow starting.

Prolonged charging with an alternator not able to provide peak voltage will ruin a battery.

As someone mentioned, a lead-acid starter battery (vs a deep cycle) will be considered a “dead battery” with even ~11V.
 
#8 · (Edited)
9696, I went back and reread your original post, when you got the truck home did you hook up the batteries to a charger? Maybe not the same as others but my thought was the alternator may not be putting out “enough” of a charge (bad). My LED voltage gauge shows the initial drop from glow plugs- then the big drop from starter, and then while running quickly increases anywhere in the range of 13.8 to 14.0 volts and holds steady. Headlights and AC on it still maintains 13.7 or 13.8 My batteries are at least several years old (?) and when working on the truck with it turned off, but cycling the ignition power on and off and glow plugs and fuel pump cycling many times over the course of 45 minutes the batteries are barely able to start the truck because of the constant drain and no incoming charge.
 
#9 ·
If a cell is shorted, it will drag the battery down. If the diode on the alternator is bad - that will also drag the battery down. In either case, you can get a jump and the batteries will discharge fairly quickly - running or not.
 
#11 ·
You guys were spot on, turns out the alt. was bad, batteries good. But, it didn't solve my problem, truck is still dead. batteries have 12.5v each. What do I do now? Still have my buddy and son in law coming over in a while, we'll see what they come up with. Thanks again



Mike
 
#12 ·
Can you describe “dead” in more detail?
Headlights work?
Dashlights turn on when key is turned?
Starter cranks or no?

I would check all connections for the items you investigated originally.
 
#13 ·
Dead as a doorknob. No headlights, dash lights/dingers, dome light, starter, nothing


Mike.
 
#14 ·
Probably burned a fusible link. Double check all your battery connections first.


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#15 ·
Went back thru all battery connections, cleaned and greased em up. I haven't checked fusible links, are they located by p.side battery?


Mike
 
#16 ·
Main fusible links come off the starter relay over on the passenger side fender. There will be a pair of them feeding the fuse box on the opposite side and one or two, (can't remember exactly) going across to the engine.
The insulation will look blistered if the fusible link is burnt out. You can also check with a voltmeter downstream.
 
#17 ·
I'll check the fusibles out tomorrow. If it is them, do I repair them, buy another wire with fusible links, never dealt with them before. Anybody have a wire diagram for this truck? Thanks


Mike
 
#18 ·
You buy another wire with a fusible link and splice it in. Alldatadiy is one source for wire diagrams.


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#19 ·
If what I'm looking at is the fuse link, it is a wire eyelet with 2 wires about 4" long crimped to it and the other end has what I believe to be the fuse link. Oh, now I see it says 12ga fuse link. Both look intact. Not sure what to do now.


Mike
 
#20 ·
I’d replace the batteries and then check the alternator. After it started, the alternator should have kept you running. A shorted battery can mimic a bad alternator. The cost and trouble of a tow are much more severe than the safe bet. Did you notice slower cranking prior to the “light-show”?

Jump starting a shorted battery may cause the battery to explode - be careful.

Good luck.
 
#21 ·
First break out a voltmeter. Measure voltage at the batteries, at the fuse box, and wherever else you can. Somewhere the voltage is going to drop off. A loose connection can cause a weird symptoms. I had a radio once that wouldn’t work. Had twelve volts at the back - with the radio off. Turn the radio on, and the voltage went to zero. Ended up being a bad connection at the fuse. Yours might be a bad ground or similar.


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#22 ·
My apologizes for not getting back to you sooner (and wasting your time), well I sure feel like a horses butt. Turns out I put the wire from the solenoid (on fender) to the p. distribution box on the wrong post at the solenoid :crying:. Put it on the post it belonged on and guess what? I finally got my truck back. Thanks for everybody's speedy and very helpful info. This website is awesome for blockheads like me :blockhead:. Thanks again


Mike
 
#23 ·
Glad you got it fixed.
 
#24 · (Edited)
Another note on batteries being "charged": I had a pair of Bosch 850cca batteries. After a couple times of the truck not wanting to start, I had them both tested. Both showed fully charged but one only had 540 amps, and the other came out at 27. Both had failed internally. Alternator was doing its job in charging. The 'good' new for me was that they were only 38 months into the 96 month warranty for pro rating. I got two replacements for less than the cost of one.
 
#25 ·
96-month battery warranty?
Thats almost 8 years.

When did that happen? 1975?

?
 
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