Strange won't start electrical problem. Short? Bad engine ground?

[bias]

If I leave the battery connected there is a slow drain.

If I turn the key to the start position I can hear the starter solenoid click but engine doesn't turn. But, then the car loses power (i.e. dome light, trunk light are out but the battery still shows 12V at the terminals (on the wire side of the terminal, so it's not just a bad connection)).

If I disconnect the batter then after a random amount of time the car gets power again (sometimes a few minutes sometimes a few hours). If I don't disconnect the battery it slow drains.

So far I've been so stupid that when the car does have power I forget to check the engine diagnostic codes (or the BOSCH injector cpu codes). Of, course then I kill it by trying to start it and when there isn't power I can't check these things.

I've tried disconnecting the fuel pump and the ignition coil to see if it was a short in either of these components. But, the behavior is the same.

The car had this exact same behavior 2 months ago and I towed it to the neighborhood shop and they told me I installed my aftermarket radio wrong but didn't tell me what they did to fix it. Whatever they did it ran for a month then had the same symptoms. However, I used very unique shrink wrap on all of the radio wires and they definitely didn't repair any of my wiring (moreover I triple checked everything and read several thread discussing aftermarket radio installation and the car ran fine for months afterwards).

Could it be that they just banged on the starter and so it worked for a month? But, it this is so why would the starter kill the vehicles power system? I really don't want to replace the starter since I've read that it's a huge PITA.

I haven't banged on the starter myself nor have I tried to push start it (there isn't really a good place for me to do this where I live).

Does anyone have advise on tracking this down? Could it be bad engine or chassis grounds (and how would I know if they are bad)? If it's a short how do I problem solve it?

Any help is massively appreciated.

[jlevie]

The battery dying when the car is parked probably means excessive parasitic draw (the current drawn from the battery when the car is off). That can be aggravated by an aged battery or a weak alternator. The "click from the starter" could be any of several things, but the known problem with battery depletion strongly suggests a dead battery.

Immediate actions at this point would be testing the battery and alternator, and replacing parts as indicated, and a check for excessive parasitic draw and repairs as indicated. Know that the two most common causes of excessive parasitic draw are a bad voltage regulator and improperly installed aftermarket electronic.

[bias]

I had the battery tested 2 months ago when the problem first happened and the test said the battery was good. Tho' the mechanic said that the test could come back good but the battery might still have issues.

I have the radio disconnected so I can't imagine how that's still causing a problem. Also, if I don't turn the key to start the car but leave it in the on position the car powers up fine (I can connect the radio harness and that works, lights work, etc.)

What concerns me is how the power system dies after I try to start the car but the battery still shows 12V. That's what made me think bad ground - it's like the car is building up a charge somewhere inappropriate and needs to dissipate before the system can be powered again.

I do recall now that even before all of this occurred my battery died (left lights on) and I jump started the car and drove somewhere 15 min away and the battery hadn't charged enough to start the car in that amount of time. Is that reasonable?

I'll bring in the battery and alternator to get them tested. I'll pull out the voltage regulator and look at the contacts before I get the alternator tested. I'll also check out diagnostic codes and post them.

Thanks!

[Hey_You]

Battery should read 12.6v if it's good

[jlevie]

A fully charged battery will have a voltage of 12.7v. At 12.4 volts the battery is at 50% charge and at 11.9v the battery is at 0% charge. So precision in measuring battery voltage is important. While it is possible for there to be a problem in the primary power/ground circuits, the battery and alternator are the prime suspects at this point.

[bias]

Sorry, when I said 12v I did mean 12.6v I was just being lazy.

Indeed, the alternator was only putting out 11v. I picked up a refurbished one at O'Reilly.

The insulation around engine ground was complete corroded and much of the wire was eaten into (looks like from an acid). I just picked up a 4ga battery wire with flat tabs on both ends and swapped that in. Now, everything works fine.

The battery was fine.