i week ago i ran some old tubing from the throttle body to the vapor canister. the tube ran between the valve cover and alt.

yesterday i installed my msd street fire box, plugs, wires and so on. it all went in and no problems. but i noticed some smoke coming from the alt/valve cover area. i figured it was from the engine since nothing was hot or looked bad.

i go out and a few hours later, i come home to this:




it appears the alt arched into the valve cover. there is no contact between them and nothing else but rubber hose inbetween.

any ideas?

 

Wow, it even burnt a hole in the valve cover. Which was lucky, as it probably fixed the short before you had a serious fire. Must have been something metallic between the alt post and valve cover. Forgotten tool maybe?

 

Not sure where/how it made contact, but this is yet another example of what i'm saying when I try to warn people about eliminating fuses/fusible links at the main power feeds to the car....

 

the wire coming from the battery to the alt is original and intact. its not exposed to anything and still in the wireloom. there is no damage to any wiring, or to the alt. no link fuses are blown. i tested the alt and battery both running and off and there is no problem.
there was nothing between the post and valve cover but old rubber hose i was using for the purge cannister. the hose was burnt into powder and blew off. it wasnt melted. i even checked to see if maybe a hood vent clip fell off between there and found nothing.
one guess is that i bent the cable at the post towards the alt casing too much when trying to read the timimg marks a week ago.

another guess is that the rubber tubing i was using was so dry and hard it acted more as a conductor more than insulation.

the fact is there was an arc between the alt post and corner of the valve cover. what exactly caused it is the mystery to me.

when i hooked it all back up and started the car it was fine and ran smooth. nothing else is damaged

 

Vacuum hose is a common tool used to diagnose engines... The hoses are placed on the coil connector and the spark plug wire is placed on the hose. The hose acts as a conductor, but the cylinder can be shut off by a test light run to ground. That's 40KV and a few milliamps... Now imagine 12V at about 600 amps...

 

so your saying the vacum hose is the cause of the contact damage?

why did it take so long when the engine was off?

i was told by a friend familiar with ignition units like msd and he said stored electrical energy went through the alt. which caused this. i find that one odd.

im contacting msd to find out. i dont want to hook it all back up and risk a fire and more damage until i know what caused it.

 

No rubber hose is going to pass welding grade amps, rubber is a insulator. Might pass some hv at very low current, over a very short length maaaaybe due to leakage, moisture etc.

Was like a bolt or something shoved inside the hose, to plug vacuum?

 

Sorry, dude, but the facts say otherwise... There wasn't a plug wire near there, only the hose, and, like I said above, it's been used for years as a proven tool to DISCONNECT the spark plugs from the ignition coil(s). You explain how only the hose was affected when it was hooked to solid lines on both ends and obviously wasn't plugged. Besides, IF the rubber WERE to act as an insulator, what would a bolt have to do with anything? The bolt would be protected by the rubber hose, would it not?

The stuff that makes up the hose makes it a conductor, not ambient environment. Granted, it's not a very good conductor, but it's still a conductor. Like pencil lead...

 

no there was no bolt. as it can be seen in the pics that was the crime scene. the hose is old and dry. it didnt melt but turned into powder.
in the pics you can see the stud where the battery power line is connected to. i was thinking maybe it grounded out against the casing.

still after sitting a few hours with not seeing anything going on, then a few hours later finding this. i just want to be sure.


the rubber bushing on the back of the alt. is melted. can i just replace it with another one before connecting the battery on, or should the whole stud assembly be replaced? the alt. tested fine.

 

Ummm... I guess electricity must work upside down over here, down under. Go get a length of rubber hose and short your battery out with it, and tell us what happens. Zip. (Just make sure it's not braided of course )

I was suggesting that maybe the hose was a vac line, that someone had shoved a bolt into to plug it, as guys often do. Scenario - hose end is cracked, hose/bolt combo manages to wedge between alt post and valve cover and pushes thru cracks in hose. Or bolt head make the short. Zap.

Unlikely scenario I agree, but the hose end waving around there does look like it has the remnants of something sticking out of it.

Edit: Sorry Tony, didn't see your last post. No hose + bolt; that was just a long shot guess. One thing's sure though - there was a hard short from the alt post to the valve cover, that blew a hole in the valve cover. And it wasn't rubber.

 

i appreciate the thoughts and help in this. if i find an answer ill be sure to share it.

 

after repairing the hole in the valve cover and the battery connect post i put it all back together. only difference was there is no vacum hose between the valve cover and alternator. i started it up and it runs great. after a while i shut it off and left it alone. nothing happened like last time.
i did take a piece of the burnt hose and through my tester, i was able to draw 4 volts off the battery through it. that is not enough to keep a hot enough arch to burn a hole in the valve cover. so, still a mystery to me..