alternator issues

[mkoch1]

So I finally got my canam on the road and even though it's not tuned correctly it's still a blast to drive. Even without getting into the boost it still a missile. Anyway my alternator works (I think) the volt gauge goes from 12V with the engine off to 14 with the engine running. I have put about 150 miles on the car in the last 2 days and every time I stop and shut the car off I have to jump-start it to get it going again. Once its jumped it runs fine. Any ideas? It's a single turbo ls1 with a tecIII efi system.

thanks,
Mark

[NAPiston]

Bad battery?

[davefiddes]

Is it dying after you leave it for a while or is it just when you turn it off? If it starts OK if you restart after a few minutes then it may be that you've got something that's drawing too much current when you think you've turned off.

One thing I have noticed is that, when cranking, my ECU (MegaSquirt) sees voltages as low as 9.2V on a freshly charged battery. The Ultima battery is very small and cranking a big V8 really takes it out of it. Is your ECU resetting a lot during the start? My tuning software can tell me this, I presume that the TEC-III stuff can too.

I've also fitted a big 70A relay in the main ignition circuit instead of the dodgy Lucas switch. This definitely has much lower contact resistance and keeps the voltage a lot higher in the rest of the loom. Others have gone further and replaced some of the main ignition circuits with thicker wiring which seems overkill but if you've got a lot of non-standard electric gizmos it might be worthwhile.

Congrats on getting your beast on the road. They all have some teething problems out of the box. You'll get them all sorted quickly enough and get back to the...

[davefiddes]

Had another thought. It could be electrical noise that's killing your car. Jumping it will hook in a higher voltage and another battery which will do a lot to suppress any noise issues temporarily. Apparently hooking up a car stereo PSU noise filter can make a huge difference to the quality of supply to the ECU.

[mkoch1]

davefiddes said:

Is it dying after you leave it for a while or is it just when you turn it off? If it starts OK if you restart after a few minutes then it may be that you've got something that's drawing too much current when you think you've turned off. One thing I have noticed is that, when cranking, my ECU (MegaSquirt) sees voltages as low as 9.2V on a freshly charged battery. The Ultima battery is very small and cranking a big V8 really takes it out of it. Is your ECU resetting a lot during the start? My tuning software can tell me this, I presume that the TEC-III stuff can too. I've also fitted a big 70A relay in the main ignition circuit instead of the dodgy Lucas switch. This definitely has much lower contact resistance and keeps the voltage a lot higher in the rest of the loom. Others have gone further and replaced some of the main ignition circuits with thicker wiring which seems overkill but if you've got a lot of non-standard electric gizmos it might be worthwhile. Congrats on getting your beast on the road. They all have some teething problems out of the box. You'll get them all sorted quickly enough and get back to the...

After I charge the battery the volt gauge shows 12 volts. Car starts fine and the volts go up to 14. I can drive around as long as I want but if I turn off the car it won't start again without a jump. After shutting it off before trying to restart the volt gauge still shows 12 volts. I hit the start button and it tries to turn the motor over a few times but you can hear it getting slower until it just won't turn over at all. I am thinking the alternator is running but not charging up the battier.

Mark

[GTR4ME]

Mark, What battery do you have? Is it a Optima gel cell, a motorcycle battery (or similar), or something else? Sounds like a weak cell, a battery lacking in cranking amps, or a bad connection somewhere not allowing full amperage to get to the starter motor.

I am also assuming this is not a starter motor heat soak issue.

[steve_D]

I had similar issues. After replacing the alternator it went away. By all indications the old one was charging but it obviously wasn't.

Steve

[Chewy]

If you let the car cool down for a few minutes does the problem still exist. A few of us have had hot starting problems, which presents its self as if the battery is flat in that it struggles to turn the engine over. When the car has been left for a few minutes the problem disappears. My problem has eased with time. I'm afraid I cant give you a definitive answer to the problem but others might as I know the problem has been discussed before.

[USCANAM]

Marl
Check the hot lead coming from the alternator to see if the nut is tight. If ok, check all connections in charging system.
The voice of experience with the similar problem at startup
Jack

[builder]

I put an engine in my truck and had that problem. Turned out to be the alternater, too. It became progressively worse and worse until it just wouldn't start. Gauge read +12 and +14 while running...until the very end when it read +9 running.

[mkoch1]

I think I narrowed the issue down to heat soak of the starter motor. I wrapped the starter motor in the aluminized fiberglass heat shield and went for a drive. Stop by my girlfriends for an hour or so, and the car started right up. Drove around for 30 minutes stopped to get gas, car struggled but started. I stopped by an advanced auto parts and they tested the battery + alternator both checked out okay. I left there and drove around for an hour, pulled into the garage shut the car off, waited 1 minute and started it right back up. Tonight was much cooler than the other days I was driving. Got under the car and the starter wasn't even warm.

Is there any airflow under the car? I was thinking about making a little scoop under the car to help force air across the starter for hot days.

Thanks for all you advise.
Mark