Help! My HMMWV is throwing major sparks and smoke out from the 200A electrical buss

[dohabandit]

My hmmwv is throwing sparks and crackling smoke from the buss bar area. It starting doing this when I was doing some above normal amount of cranking.
The reason I was cranking it longer than usual was because I drained out some old diesel, put in a new fuel filter/strainer and needed to bleed out the fuel system. Per the TM, just take the lead off the MFI pump solenoid and crank it until the fuel arrives at the bleed screw (I put a tube in there and let it run into a bucket, then closed the bleed screw).

I then reconnected the MFI pump solenoid lead and decided to try to start it up. It cranked a bit and then almost started. So I let it sit for a bit, don't want to burn out my starter with too much cranking.

I then tried to crank it and BZZZZZT!!!! CRACKLE!!! SMOKE!!! blowing out from the buss bar area (battery box cover was open). I almost thought a wrench had fallen in there and made contact between the chassis and a battery terminal. It was quite a light show really, like 5-6" sparks showering.

It looks like the issue is where the POS battery cable is connected to another cable on the side of the wall forward of the buss bar. What is odd is the pics I see from the TM show a vertical bar and a horizontal bar. On my truck there is only the horizontal bar. Where the vertical bar is located there appears to be bolt that has the two POS cables attached to it. I have always puzzled at this because it seems like it is attaching the POS to GND! Is there some sort of insulator under there or something? It is gooped up with some sort of black tarry substance so I am not really sure what is going on under there, but will disassemble it tomorrow. I do know that my cables aren't in the best condition. I ordered a couple off ebay, but I only saw the short length ones. If anyone has the longer length ones, please let me know...

What a bummer today has been... I hope this doesn't mean my starter is toast.

Any expert advice out there?

 

[dilvoy]

That "bolt" is probably the through hull connector. Positive from the battery to the stud then on the engine side of that connector a wire goes from the stud to the starter main power connection. Early Humvees seldom have that buss bar. Your sparks may be from a loose battery cable connection to a battery terminal. You probably got the cables and things hot and they can throw sparks and melt the battery terminals and actually fuse a terminal to a battery stud if you have a loose one. I've ruined one battery cranking with just a pressed on and not tightened terminal.

 

[dohabandit]

Thanks for the response,

The terminals on the batteries all look good, tight, no corrosion, etc. Nothing fused to anything it shouldn't be.
The cables are another story. I will wait for the new cables to come in and take all the terminals off, wire brush the contact areas, and then put it all back together.

The thru hull connector is where it seems like the sparks are coming from. One of the cables attached there goes to the slave receptacle. Should I remove all the good and clean that up and inspect it? How does that connector remain isolated from the chassis, is it sleeved with some bakelite insulator or something?

The first time it sparked, I thought as you did that maybe it was hot. So I let it all cool down, looked everything over and didn't see anything that looked like it was an issue so I cranked it and more sparks are showering.
I don't think the issue is that its hot. I have a feeling that something is wrong in the area of the through hull connector. Could this be caused by a seized up starter motor?

 

[Jeepsinker]

No the starter is more than likely fine. You have a bad connection somewhere there. You must have gotten something hot and melted an insulator or part of a connector that you haven't seen yet. You need to take all of the cables off of the hull connector and inspect closely.

 

[dilvoy]

The through hull connector is a stud that is isolated from the hull with, for lack of a better word, large plastic threaded body. There is a nut that holds it on the engine side. It is a commercially available item. Nothing special about it really. A boating supply catalog should have them in many different sizes. I remember mine having a retaining nut that was what they use on electrical boxes. Low tech, but it did the job. Maybe one of the cables on either side was loose and things got hot and the plastic melted and the stud of the through hull connector has moved and is grounding on the body.

 

[Retiredwarhorses]

Like Dilvoy said....the power stud passes through the tub from the battery box to the other side to the pos stud to the starter, its possible it is now in contact with the body, remove all of it and replace/Inpect the stud and the plastic isolation pieces. These items need to be tight. Look at the TM for the proper unit to replace and the washers used.
i usually replace these on my restorations....