Im looking at an 83 Z-28 with an LG-4 and a 700-R4. Really the only thing wrong with it is that it keeps draining batteries while its running. If you put in a fresh battery, it will start and run fine but drains it real quick. The alternator was supposedly tested and deemed good. What could cause this? Would something like this probably be related to wiring under the hood or could it be anywhere in the system? I do have a known good engine harness and ECM from an 84 Z with an L-69. Would rewiring the engine bay be a possible cure? Thanks in advance.

 

Check the grounds and all the leads running off the battery.

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

TTT

 

If drains while it's running, the alternator isn't any good. If it drains while the car is off, something is pulling juice from the battery(I'm guessing this is the case). I've seen a bunch of alternators suck juice from the battery while the engine is off, so you might check that out. To test, just unhook the alt. when the car is off and see if the battery is still going dead.


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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, currant red metallic paint. Lots of other stuff...
82camaro

 

Easy alternator test:

Put a voltmeter on the battery with the engine off... you should get 12 volts. Take off the meter.

Start the engine, and put a voltmeter on the battery- if you're not seeing above 13.5 volts, the alternator's not doing anything worthwhile.


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-Tom P (Hot rodded 1986 Firebird 2.8l)

 

So if the alternator is sucking current with the engine off do I just replace the alternator or is there another solution?

 

This happened to me 2 weeks ago, the positive battery cable had become loose. Just tightened it down and voila, no more drained battery.

 

Does the "Choke" light come on when you turn the key on with the engine not running? If not, the alternator will never charge, because it doesn't "know" the key is on... it gets that "information" by way of receiving 12V through the light bulb. So, if the "Choke" light (which is also the "Alternator" light - don't get me started) doesn't come on, put a new bulb in there, and then see if the system starts to work. I've known more than one person to go through several rounds of unnecessary and expensive battery-alternator-starter replacement, because their bulb was bad.

As stated before, check all your connections at the battery and alternator for being clean and tight. That's something you should do regularly anyway, at the same time you do a tune-up.

OBTW... I don't recommend rewiring anything, ever, unless you really know what you're doing. Not to be insulting, but if you're having trouble diagnosing a dead battery, you probably don't have the skills or tools to improve on the wiring that's already there, and would do more harm than good by hacking on the wiring. Except for the one oddity about the indicator light, the factory wiring design is just fine. Find the problem and fix it rather than trying to rig something.

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"So many Mustangs, so little time..."
ICON Motorsports

[This message has been edited by RB83L69 (edited November 21, 2001).]

 

Thanks for all the constructive replies guys.
And RB83L69, I didn't mean start hacking up the harness, I just meant get a new engine harness. I already have one sitting in my garage that came off a car that ran right. I have no intentions of ever ethnically rigging some half-assed wiring on any of my cars. And I don't want people thinking Im some sort of imbecile. My first guess was the alternator as well but the seller swears up and down that the alternator is good. I was just looking for some suggestions.