So ive been working on a my 1985 z28 with a 283sbc that i bought. I replaced everything from the Carburetor, Starter, Alternator, Filters, Flashers etc. It draines like crazy. I could drive it for a good while but once i shut the car off it wont crank back up as if it has no power but the lights and everything works. Interior lights and headlights are still bright. Ive run out of solutions to get it back to normal and im no mechanic i dont have anyone to help me so far so thanks in advance.

 

First things first, how much voltage is the alternator putting out? Check it at the battery with a voltmeter, it should be at least 13 volts or more at idle.

 

When the car is on the gauge shows a good reading more than 13 volts. Do you think it's heat soak?

 

No.

Not least because THERE IS NO SUCH THING. That's only a technical-sounding myth invented by people who refuse to even try to understand electricity, perpetuated by Friday night McDonalds parking lot monkey-spank and intoned with deep reverence and religious awe by the same people on the Internet, and then taken advantage of by unscrupulous vendors (or those who have just given up on the truth and decided to just hold their nose and adopt a "sell em what they ask for" attitude) as a marketing tool.

Put that myth out of your mind.

13V is not necessarily a "good" "reading". The "gauge", if you're talking about the thing in the dash, is NOT an "instrument"; it's a trim package.

You need to know the ACTUAL VOLTAGE in a few critical places, measured with a piece of ACTUAL TEST EQUIPMENT.

Using a DMM or similar, get the following voltages:

Across the batt terminals with the car not running
Across the batt terminals while starting
Across the batt terminals with the car running
DC voltage between the big post on the alt and the + batt terminal with the car running (expect something in the neighborhood of .05V to .2V)
AC voltage as above (expect about a quarter of the DC voltage or less... a very low voltage)

 

I will have to try that and get a real reading from the voltage meter. But this is truely bizzare because everything works just fine when im able to drive it.

 

The measurements will help figure it out. Or at least, rule out a few things.

 

Ive done a Parasitic Amp Draw Test and its at 4.00A . After i pull the CTSY WDO FUSE it goes down to 3.86A. Thats the only fuse that makes a difference. Maybe some sort of ground somewhere.

 

4A is a YUUUUUUUUUJJJJJJJJE drain. 50 - 100 times what there should be.

What about the list of voltages?

 

Ill have to go back and get the voltages was caught up in finding that fuse draw. But i know with the car off the battery read 13.7.