Fire.....well amost

[oboyjohn]

In my many years as a mechanic, civilian and military, I have seen electricity do some very weird things. When I was learning the trade in High school, our teacher would put faults on stand mounted engines. When my turn came, he said that the client was complaining of a no start situation, but the engine cranks. I did the usual checks and decided to crank the engine to "just try it". The engine cranked for 2-3 seconds and started running. Running, but very rough, like the timing was way off. The teacher came over when it started and said "that was fast. What did you find?'. I told him I did the usual checks, cranked the engine over, and it started. He looked at me surprised, shut off the engine and showed me what he had "sabotaged". He took off the high tension wire from the coil to the distributor, and showed it to me. The wire was not an actual wire but a rubber vacuum hose almost 2 feet long. That coil must have been really good to generate a spark strong enough to make that jump in the hose! And that was my introduction to "weird things that electricity can do."

 

[sermis]

Well here is the contact point. Top side of passenger frame rail. No brake line in site. Transmission lines close but they didn't contact. I'm guessing the voltage went into the frame rail then jumped somewhere to either the left frame rail or just into one of the brake lines. The brake lines made the final ground back to the negative cable on the battery. Thing I don't understand is doesn't the battery dead ground to the passenger frame rail?

 

[Retiredwarhorses]

Well here is the contact point. Top side of passenger frame rail. No brake line in site. Transmission lines close but they didn't contact. I'm guessing the voltage went into the frame rail then jumped somewhere to either the left frame rail or just into one of the brake lines. The brake lines made the final ground back to the negative cable on the battery. Thing I don't understand is doesn't the battery dead ground to the passenger frame rail?

No...the grounds all lead to a different point based on the engine and model year of the truck, but. They all lead too the engine.

A0/A1 is from battery box to the shunt to the starter ground and runs through the engine harness.
A2 NA 6.5's to the right rear of the head stud, then to the starter
Turbo diesels from the shunt to the front right of the motor stud and then back to the starter.


Changine the frame rail rail brake line is easy...the others except for the fronts under the cooling stack are a bit tougher.
nows your chance to install flexible brake lines instead of the hard lines at the calipers....makes for pad changes so much easier. Blue hummer sells a flexible braided brake line kit....

 

[Retiredwarhorses]

As far as the broken bolts, weld a nut and try and get them out...this area is under exretme pressure and torque due to the starter weight and torque of cranking the engine....

 

[sermis]

I would weld it but they broke about 3/8" inside the bolt hole

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[snowtrac nome]

take and center punch it pilot drill right down the center than try a reverse drill bit 90 percent of the time the bit will bite and pull the residue right out. The key is being as close to center as you can.

 

[doghead]

If they are broken deep enough, you can drill out a bolt ahead of time, cut it off about an inch long. Then, thread that into the hole and use it as a centering guide to pilot drill out the broken bolt. It will keep you centered much better than trying to do it "freehand".

 

[Retiredwarhorses]

I have used this method before, but not on starter bolts

https://m.youtube.com/watch?v=v8KEzbJvqEE

 

[CMPPhil]

That is a neat little video, thanks for sharing.

Cheers Phil

 

[Action]

Has anyone mentioned that the trans and t/c cooling lines are what runs down the rail near the starter? The brake line is on the other side of the frame.
Also, I haven't seen AMG brake line clamps with rubber on them. They are metal only and bolted to the various spots.

 

[TOBASH]

this is very similar to what I have described elsewhere. If you can get a Dremmel in, cut a 90° crosshatch. Use a flat head screwdriver or cut the tip off of a Phillips head, and twist the bolt out after heating with a blow torch and then using anti-seize spray.

If you can't, drill two holes in a line, next to each other. Then either use a flat head screwdriver made for anti-theft, or use a saw to cut out the center. Plug the 2 tines of the fork you just created into the holes you just drilled, and turn.

RWH has posted a terrific video. In many cases you will not be able to fit a drill or Dremmel. use that video and buy some small hooks.

T

 

[Ddk2001]

I have a question. I've never re-wired a car or truck - but have done so on a few boats I've owned. Multiple batteries, charging relays, and the like. It's an ABYC requirement that overload protection be located within 7" of a power source on a boat - including starting batteries. On my boats - I always installed a 250 amp fuse on the starter cables - and house batteries. Fires on boats = bad news - so the overload protection will break the circuit if arcing occurs - preventing what happened here to the OP.

I was always amazed at how little amperage some starters pulled. Momentary amperage spikes aren't a problem - the fuses are capable of handling the few millisecond spikes when starters crank.

I get why the military doesnt have fuses fuses all over these trucks - but I wonder whether overload protection at the battery would be a good idea.

250s are the biggest I've used - but you can get 500s, 750s, etc.

 

[sermis]

One down one to go. I tried a pick and turning first. It would move a little then bind. Able to drill just enough for the easy out to bite.

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[sermis]

Glad they didn't use any thread locker. Really want too bad. Just enough drill for the ease out to grab. Almost could have used the picks of it would have had something to grab.
Note Brake line replacement and see what else is fried

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[sermis]

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[Action]

Have you figured out why the brake lines cooked yet? They are not near the starter....

 

[TOBASH]

Glad they didn't use any thread locker. Really want too bad. Just enough drill for the ease out to grab. Almost could have used the picks of it would have had something to grab.
Note Brake line replacement and see what else is fried

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Good for you!!

 

[86humv]

If this happened before my texas trip last week...I could of brought a new long brake line, and new starter bracket, and more....I was in Temple Friday 3/24.

 

[sermis]

Well the starter is back on and the truck fired right up. Checked the charging voltage and it seams to be OK and no spikes from the ALT charging.

GROUNDS were mentioned. I have CRS going on and forgot that I had made and installed the grounding harness for this truck..
Everything is grounded to the back of the engine. Grounds from control box, dash, ALT, battery, All run to the back bolt on the engine. Starter is also grounded straight to the battery.
Only thing I can think of that might would help is a ground wire to both frame rails.
Best I can tell is when the starter fell on the right frame rail and shorted direct into the frame the voltage arced to the left frame rail where the brake lines run, than arced to the brake lines which grounded back to the truck. The brake lines couldn't take the voltage and got hot and melted......

Best advice I have at this point is check the back bracket on the starter and make sure that the stud into the bracket is tight. Had this bolt been tight on the truck the starter would't have fallen off.

 

[Bravojmc]

Well the starter is back on and the truck fired right up. Checked the charging voltage and it seams to be OK and no spikes from the ALT charging.

GROUNDS were mentioned. I have CRS going on and forgot that I had made and installed the grounding harness for this truck..
Everything is grounded to the back of the engine. Grounds from control box, dash, ALT, battery, All run to the back bolt on the engine. Starter is also grounded straight to the battery.
Only thing I can think of that might would help is a ground wire to both frame rails.
Best I can tell is when the starter fell on the right frame rail and shorted direct into the frame the voltage arced to the left frame rail where the brake lines run, than arced to the brake lines which grounded back to the truck. The brake lines couldn't take the voltage and got hot and melted......

Best advice I have at this point is check the back bracket on the starter and make sure that the stud into the bracket is tight. Had this bolt been tight on the truck the starter would't have fallen off.

Good to here she fired up and your getting things fixed. Also glad she didn't burn to the ground, no pun intended.