Dead Battery

[Tom Northcott]

Recently my 1971 LS-5 has been throwing me a curve ball. When the car is cold it starts right up, I drive it for 10-15 minutes shut it off and let it sit for a few minutes and when I go to restart it the battery is not strong enough to turn it over. I replaced the starter, battery and checked the alternator, which seems to be working properly.

If the car sits for a few hours after driving it, it starts right up again? It only acts like a bad battery when the car is warm. Any help would be appreciated.

[Roy B.]

Re: Dead Battery

Many people don't think they are bad inside because they only see the ends CABLES cant carry the AMPS any more.

[Tom Northcott]

Re: Dead Battery

I thought that may be the case, but as you said, they "looked" good. The other reason I discounted that is due to the fact it starts cold, but not hot. You would think the starter would draw less amps cold than hot, but obviously that must not be the case.

[Roy B.]

Re: Dead Battery

When HOT is when bad cables show up

[Greg Pic 39571]

Re: Dead Battery

If present in your year change the fuseable link

[Alan Drake]

Re: Dead Battery

OK you cleaned the cable connections even if they looked good.
Have seen the starter being installed too close to fly wheel and when hot the clearance decreases between the two to a point that nothing moves. Some engines have shims (BB) to avoid this problem.
But lets find the problem first, measure the current when cold and then when it doesn't want to start. This simple measurement will start you in the right direction instead of spending on unnecessary parts.
Good hunting.

[William C.]

Re: Dead Battery

Pay special attention to the ground to the frame under the battery. You are dealing with copper-clad aluminum cables if the factory set, and the only protection against the corrosion of the aluminum is the dip solder covering the end of the cables. This is neither foolproof nor everlasting. In my '72 when I had it the cables had turned to powder at that point, but the car still started. I may have had a week left to go before failure.

[Mike S.]

Re: Dead Battery

Tom. to check your battery cables.with a volt meter check battery voltage.should be around 12.4 to 12.6.then check voltage at starter end of positive cable with a load on starter (starter engauged).the voltage should be with in .2 (2 tenths)of a volt of battery reading.if reading is lower cable is bad. you can check neg. cable the sameway.Mike

[Wayne P.]

Re: Dead Battery

This is a common BB problem due to heat soak of the starter. You need a heat shield, at the very least. If you're running hearders you can expect even more problems.

[Wayne W.]

Re: Dead Battery

You might just check the timing. If it is kicking back hard at hot start, sometimes the timing is too high.

[Philip C.]

Re: Dead Battery

Hi Tom take the air cleaner off when you shut the motor down and see if any vapor is coming from the carb it could be leaking down this will give a hard start. Good luck Phil 8063

[John O.]

Re: Dead Battery

Hi Tom

I had the exact same problem with my 1956 Chevy..Although I have a semi built 350 engine..I changed the battery cables using thicker ones. Now it starts up cold or hot with no cranking problems.

Just my 2 cents...............John