My problem sounds kind of like the other alternator thread, but I have already had the alternator checked out by a reputable local rebuilder and its putting out 140amps. There are no obvious wiring issues, though I'm suspecting that is where the problem is.

Cold, the car starts fine...once it warms up, it is very slow to restart and sometimes won't start at all. The voltmeter has gone from being around 13-14 volts to barely 12, and it doesn't feel like the car is running to its potential so I know it isn't the gauge. The starter is a new Summit unit. I did have an older battery in the car that had been unused for several months (charged it first),and I am wondering if that may be the issue. I'm putting the alternator back on tomorrow and seeing how it does with a new battery. The engine was out recently, so I may have pinched a wire somewhere...any ideas? Before now I have never had charging issues with any 4th gen (have had three of them).

 

It sounds like it takes longer to fire up, Is that correct? Does it rotate the engine as fast after it's hot as it did when it was cold ?

Have you checked the ground strap from the body to the engine at both ends for cleanliness and being tight?

 

It turns over much slower when hot. Good idea on the grounds, I'll check that.

 

The only thing I have ever seen give a rotational problem once the engine was hot is a starter. They get fried from the headers. You sure yours is ok??????

 

I would suspect the battery also.

 

Its a new starter from Summit, and I don't think thats the problem since there is a low voltage condition all the time. I'm off tomorrow so I'm going to put the alternator back on and try it with the new Optima battery.

 

Wait. If the alternator was bad, the battery would not be charging. Therefore eventually the battery would get low and there could be no cranking even when cold. Understand?

You only mentioned a hot problem. If you have a hot problem but after cooling down,it's ok, it's not the alternator.

Let's cut to the chase. While cranking it over from dead cold. Measure the voltage across the battery while someone cranks it over. Be sure the voltage does not drop below 11 volts.

After the engine starts, measure the voltage across the battery and confirm it's at least 14 volts. This confirms battery and alternator health.

Now the next time you have a "hot cranking" problem, measure the voltage across the battery and see if it drops much lower than before (when viewed cold).

I'm curious about a low voltage all the time, as you put it. When you suspect a low voltage, what is the actual voltage when measured across the battery?

 

The alternator checked out ok, and I put in a new Optima battery, and the car is fine now. The gauge still looks a little low to me, but it isn't giving me any more trouble.