Working On HMMWV - Need Help

2,967 Views | 7 Replies | Last: 3 yr ago by hawk-aggie
hawk-aggie
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AG
I've got a little problem, Ags. I'm working on a 1980s HMMWV that has an electrical issue. I would like some help from any of you who have first-hand experience. Long story as short as possible below.

Unit has been operational in the past.
Unit saw a lot of sand and salt water exposure with the Teams.
Unit just recently started having issues upon start. Before this it was working and running fine with a jump start.

First time, was using a slave cable to get power from another Humvee. The two were jumped together for about 20-30 minutes to charge batteries. Turned ignition to "wait" position; heard some sort of ticking noise; "wait" light went off, move ignition to start. Engine fired and was running while I disconnected the slave cable. Engine quit, then smoke started coming from OLI on winch. (Note: Ignition switch installed at the time did not automatically spring back out of the "start" position. It had to be turned back manually.) See photo below.

The place where it caught fire is at the upper left corner. Got batteries disconnected and doused the fire.

I disconnected the two cables from the starter that go to the winch. (Repairing that is a separate issue that should be pretty straight forward.) Cleaned up the connector posts on the starter and repaired one of the ground connections.

Second time, slave cable connected; batteries hooked up; ignition switch to "wait"; smoke started coming out from under the "dog house" inside. That black object with the "t" top is an RPM sensor that might have experienced the smoke test. See photo below. Looks a little crispy, don't it?



Third time, no slave cable; batteries connected, and the diagnostic connector forward of the gear shift started smoking. I disconnected the batteries, removed the cap on the connector, and now you can see in the photo below what I saw when I did so.

It'd be nice to know to what that pin connects.

Obviously, there may be a short somewhere, but it would be helpful to know where to start. I have a new ignition switch. I plan on getting a new RPM sensor. I'm going to do a couple of starter checks to make sure the positive strap from the starter to the solenoid hasn't lost its insulation and is creating a short.

Engine is a 6.2L version. Batteries have a little less than 10 volts each. High amp alternator works fine. Is this a starter issue? a control box issue? a battery issue? If you've got some operational maintenance experience, I'd like to hear your ideas.

PM me at mark96ss at hotmail dot com. Thanks in advance.
IWannaGoFast1
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AG
Mod Mafia out of Magnolia seems to know their stuff. I'm sure they'd charge a pretty penny for it, but I don't doubt that they could fix it. One of the owners, Mark, is a former student, too.
JABQ04
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AG
Shouldn't have put the fire out........
hawk-aggie
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AG
Update: The RPM sensor shown in the 2nd photo was only caked with oily sand. Made it look a bit like it had gotten fried. Replaced a faulty ignition switch and gave the batteries a charge yesterday. Today, we're going to see if the smart box is working properly.
AllTheFishes
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AG
deleted
CT'97
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AG
I can't provide specifics but from experience managing an aged HMMWV fleet you will need to buy two more and between the three of them you will keep one running.

-originally posted this from my wife's account because it was still logged on.-
hawk-aggie
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AG
Well, I guess we are beating the odds so far. We have 5 Humvees, and this is the only one that isn't running right now.

Smart box appears to be working. Starter is going in for a repair/rebuild.
Gunny456
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AG
Hawk. I have restored two M998,s and one M1044. My first guess would have been the smart box. I had one with a similar issue. One of the issues was the grounding straps that were causing very high amperage. They are notorious for poor grounding and there is a kit available that fixes that issue. Even though you think the smart box is testing good it may not be or could be the controller. Check the grounding issue first.
Good luck.
On a different point install a battery cut out switch if you don't drive it much. The smart box always drains some current even if the switch is off and will drain your battery......you may and probably already know this.
hawk-aggie
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AG
Gunny,

It appears the culprit may have been the starter. We think it had an intermittent short. We got it rebuilt, reinstalled it today and jump started it. No smoke anywhere. Ran like a top. Smart box appears to be operational. High amp output alternator putting out lots of juice. Thanks for reminding me of the battery draw. I'll disconnect the batteries. On to the next issue.....
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