Starter Heat soak or something else?

[badazz81z28]

So after my car has been running a while and go to crank it back up the starter acts like the battery is low or the engine is a high compression engine slow to rotate. I suspect starter heat soak, but did not have this problem with the LS1. Nothing has changed except the LS7 engine. Would the LS7 just be putting out more heat? Or is something else going on?

[andrewb70]

Double check all of your grounds and the hot lead to the starter.

Andrew

[icemanrd19]

Triple check grounds. Did you install a new front runner at the same time? Powdercoating on it could cause this issue not allowing the alternator to be fully grounded. Also I heard a few cars after being ran on the autocross track having that same issue

[dhutton]

If the LS7 generates more horsepower then it generates more heat. GM installs a heat shield on the LS3 starters for a reason but it may not fit with your headers.

Don

[reedld]

Can you get a DVM on starter when you experience the problem? I experienced this issue 2 years ago. I got the DVM leads on starter, turned key, found that I was getting a voltage drop. I installed a waterproof relay. Bought a kit from this company....

http://www.ceautoelectricsupply.com/

https://ls1tech.com/forums/conversio...rter-soak.html(Post #4)
Good luck!

Leon

[badazz81z28]

Copy that, if it was connections or grounds would It only do it when hot? Would tuning cause this at all? Like spark advance?

[andrewb70]

Copy that, if it was connections or grounds would I only do it when hot? Would tuning cause this at all? Like spark advance?

It could, but generally the cranking spark advance is the same regardless of temperature (in the tune). You could try reducing the spark advance while cranking, a little, and see if that helps.

Andrew

[parsonsj]

We need more data. Can you get resting, cranking, running (at idle just after starting, especially) voltages at the battery and alternator posts? I'm speculating, but I wonder if your alternator is charging your battery enough while you're driving. You should see 14.7V coming from the alternator post after the car starts, and a solid 14.4V at the battery, that slowly recedes for 20 minutes or so down to about 13V.

See here for a great writeup on typical GM alternator failings:

https://www.corvetteforum.com/forums...nator-fix.html

[icemanrd19]

Again. Did you install a new front runner at the same time?

[badazz81z28]

Again. Did you install a new front runner at the same time?

Right now I'm still using the C5 set up. I know I have 14 volts in the dash gauge while runnng. I'll see what's at the battery.

[reedld]

Don't forget to check the voltage of the purple solenoid wire at starter. You may have proper voltage at battery and dash/ignition switch, but the long run from the ignition switch may be the issue. Electrical wiring was not the greatest in the 70's. The relay trick also works with headlights. There is a HUGE voltage drop from the dash switch to the actual headlamps, not enough to cause the headlights not to work but enough to make them dimmer than you are used to with modern cars. You'd be surprised what a few volt less will do.

[icemanrd19]

My purple wire at the clutch safety switch came out alittle. After driving it would sometime not start. Acted like the battery was dead. Found out only half the wires were still in the connector. Fixed the connector and bammmm. Starts perfect everytime now. Weird thing is it only gave me problems after driving for awhile and i thought it was heat soak.

[badazz81z28]

Don't forget to check the voltage of the purple solenoid wire at starter. You may have proper voltage at battery and dash/ignition switch, but the long run from the ignition switch may be the issue. Electrical wiring was not the greatest in the 70's. The relay trick also works with headlights. There is a HUGE voltage drop from the dash switch to the actual headlamps, not enough to cause the headlights not to work but enough to make them dimmer than you are used to with modern cars. You'd be surprised what a few volt less will do.

The harness is a painless (all new wires). Didn't act like this with the LS1 so the heat soak was my first guess.

[reedld]

What I meant to say was "70's electrical engineering" was not as good as it is today. The new painless wiring harness is great but it still has a decent run from switch to solenoid. I was lucky enough to catch mine acting up in my garage, clipped on DVM leads, rested DVM on cowl so I could see voltage when I turned the key. Having a helper would make this easier. If it is heat soak, running the new solenoid wire from the front of the engine allows the wire to farther away from headers. The actual connection distance doesn't change...I put my new wire in a reflective heat barrier as well. I could send you a pic since Photobucket blows..

[badazz81z28]

Confirmed I have over 14 volts at the battery while running.

[parsonsj]

Ok, next bit of data to check would be to see what the battery voltage is with the car off overnight. Turn the headlights on for 15s, then turn them off and measure the battery voltage. We're looking for a number of 12.6 or slightly above.