Weird short

[engineeradam]

I have a 1987 6.2L, that wont start. Randomly it just started shorting out. When you turn the key on, the lights come on in the dash like normal and everything is fine. Then when you crank it over it sounds like the batteries are almost dead, but in fact there grounded somewhere. The truck wont start and the cab to air intake ground strap gets red hot. Ive traced the purple ignition wire and there seems to be no breaks in it. After some testing ive come to the conclusion the problem is beyond the firewall and in the engine bay. Any suggestions? Im stumped.

[DmaxMaverick]

Make sure your battery ground cables are really grounded, and where they belong. It sounds like your starter is grounding through the chassis, and not through the batt- cable grounded to the engine (intake bolt, normally) like it should be. If both your batt- cables are attached to the frame, the starter will have to ground through the bonding straps, from the body, which will not be sufficient current. The system works better if both grounds are to the engine, and bonded to the frame and body downstream.

[engineeradam]

Thats exactly what it was, thanks alot.

[trbankii]

Hmmm... Sounds exactly like my problem. Yesterday, parked the truck in the driveway with no problems after running around all day. Less than an hour later I go out and it won't start. All normal while the glow plugs cycle, but try to start it and everything goes dead and the dash lights go off.

Checked all the battery cables - positive and negative. All looks secure. Will pull everything apart, clean it, and put it back together just to make sure. But what would be the next culprit? I'm thinking starter solenoid?

Headlights are bright before starting, so doubt a dead or shorted battery. After trying to start it, the headlights don't even glow.

[trbankii]

Just to follow up...

Turned out to be TWO dead batteries. Both 770 CCA 78 series batteries tested with under 100 CCA - only two years old. I've never had a battery completely die like that, much less two.

Needless to say, very relieved it wasn't anything more serious!

[JohnC]

Turned out to be TWO dead batteries. Both 770 CCA 78 series batteries tested with under 100 CCA - only two years old.

Maybe a "stupid" question, but did you fully charge the batteries before testing?

[trbankii]

Saturday I had been running around all day. No struggle to start at any point or any other sign of problems. Parked in the driveway and then less than an hour later went out and absolutely no start. Glow cycle and then just a click when I tried to start it up.

Initially the headlights were bright, but everything would be "dead" for a few minutes after trying to start. It was dark, so I left it for the night.

Sunday there was nothing. No headlights, no dash lights, no click. So I put it on the charger overnight.

Monday we were back to headlights, dash lights, and click. So I switched the charger over to the "start" setting and gave that a try. No luck.

Took both batteries in to BatteriesPlus and they ran the tests. Said both batteries were dead - less than 100 CCA on each and that charging wouldn't help that. So two new batteries for $80 plus change with the warranty pro-rating. Brought them home, threw them in, and started right up.