C6 z06 starter heat soak issue

[froggy47]

Hi guys, been a while, looking for Paul or LLC5 if they are still active here. This is a widely experienced, if not known to GM, problem on the 427 motor and as recently as yesterday I was instructing in a 2016 Camaro ss automatic (466 hp engine - not sure the cubes) and EXACTLY THE SAME issue came up.

1) Cold starts 100% fine.
2) Hot starts engine at full op temp, shut off for 5-10/15/20 minutes crank over extremely/barely and may start eventually or may throw a xmas tree on the dash & multi codes.
3) Wait till engine cools 1/2 hour or more, starts fine.

What I have done.

0) Car is 2013 z06 9k miles east coast some normal corrosion (ugh) hate east coast cars. Bought at dealer auction.
1) 2 new batteries, so don't tell me it's the battery or connections, I know how to connect a battery.
2) Installed DEI heat shield on cat next to starter.
3) Tried to remove starter & could not wiggle it out between block & cat.
4) I did find a loose (hand tight) power cable to the starter, secured that but no fix.
5) I have a new(not rebuilt) starter ready to go. I think if I loosen the exh manifold & pipe near cat I can get the wiggle room to install it. The 02 sensor wires are short & impossible to access by a normal human.

Any help please?

Thanks.

[LLC5]

Hi guys, been a while, looking for Paul or LLC5 if they are still active here. This is a widely experienced, if not known to GM, problem on the 427 motor and as recently as yesterday I was instructing in a 2016 Camaro ss automatic (466 hp engine - not sure the cubes) and EXACTLY THE SAME issue came up.

1) Cold starts 100% fine.
2) Hot starts engine at full op temp, shut off for 5-10/15/20 minutes crank over extremely/barely and may start eventually or may throw a xmas tree on the dash & multi codes.
3) Wait till engine cools 1/2 hour or more, starts fine.

What I have done.

0) Car is 2013 z06 9k miles east coast some normal corrosion (ugh) hate east coast cars. Bought at dealer auction.
1) 2 new batteries, so don't tell me it's the battery or connections, I know how to connect a battery.
2) Installed DEI heat shield on cat next to starter.
3) Tried to remove starter & could not wiggle it out between block & cat.
4) I did find a loose (hand tight) power cable to the starter, secured that but no fix.
5) I have a new(not rebuilt) starter ready to go. I think if I loosen the exh manifold & pipe near cat I can get the wiggle room to install it. The 02 sensor wires are short & impossible to access by a normal human.

Any help please?

Thanks.

I hate to say it but your #2 problem indicates a low voltage issue. Charging system voltage when hot and under a load with all accy's on should be checked (above 13.0V) and load test any brand new battery with a carbon pile load tester. When this problem is active you should check the voltage at the battery clamps and compare it against the voltage at the clamps when it starts good. It could be a bad starter also, but at 9K miles it would be rare.

[froggy47]

Thanks.

So if it is a low voltage issue, why does the voltage "fix itself" after cool down. I know a hot engine requires a bit more electrical power to turn over than a cool one (not counting sub zero condition) but this is like night and day. One guy on CF (there have been many suggestions) said that the hot/power stud on the starter gets "loose" or partially disconnects somehow under hot engine condition & when cooled down makes better contact, possible?

[LLC5]

Thanks.

So if it is a low voltage issue, why does the voltage "fix itself" after cool down. I know a hot engine requires a bit more electrical power to turn over than a cool one (not counting sub zero condition) but this is like night and day. One guy on CF (there have been many suggestions) said that the hot/power stud on the starter gets "loose" or partially disconnects somehow under hot engine condition & when cooled down makes better contact, possible?

Not possible if the connection is good clean and tight. Batteries can recover just enough voltage after sitting to start a vehicle and your description of lights flashing and codes indicates low voltage. I am not saying that your battery is bad, just have it properly checked with a real carbon pile load tester to take it out of the equation. As an example, if you have a 800CCA rated battery it should load to 400 A with voltage above 9.6V for 15 seconds. Let the carbon pile cool down and do it again. A good battery will easily pass. If the tester does not have huge cables attached to the battery it is not a quality carbon pile tester. Your starter could also draw down the voltage enough to set codes and flash lights if it is internally shorted, it is rare but not impossible. Check the voltage at the battery cables with the problem active (preferably after the battery test) and see what you get.

[froggy47]

OK, Thanks, the time the dash lit up I KNOW voltage was nil. I had failed to reconnect the alt wire so battery was not charging (My bad & no facts withheld even if they make me look bad haha). I bought a brand new one it's correct spec for the car 590 crank amps and you may know in the back it's hard to find one that fits in the hole. So now I no longer get the xmas tree, just slow turn over. BTW the nut on the power stud on the starter WAS hand tight when I first went to it, of course that is now corrected. I put a DEI cat shield over the cat. Still it happens. I instructed in a 2016 Camaro SS last Sunday. EXACT SAME slow crank when hot engine.

Thanks.

[LLC5]

OK, Thanks, the time the dash lit up I KNOW voltage was nil. I had failed to reconnect the alt wire so battery was not charging (My bad & no facts withheld even if they make me look bad haha). I bought a brand new one it's correct spec for the car 590 crank amps and you may know in the back it's hard to find one that fits in the hole. So now I no longer get the xmas tree, just slow turn over. BTW the nut on the power stud on the starter WAS hand tight when I first went to it, of course that is now corrected. I put a DEI cat shield over the cat. Still it happens. I instructed in a 2016 Camaro SS last Sunday. EXACT SAME slow crank when hot engine.

Thanks.

Have you installed the new starter yet or just tighten the main battery cable nut? It could be your starter, but I would want to know that the battery tests good, I have found quite a few bad new batteries. If they sit on a shelf they sulfate and go bad internally, I would also check the born on date of your new battery. Make sure that the battery clamps don't twist when the bolt is tight, a tight bolt does NOT mean a tight clamp on the battery (ask me how I know). How do the negative and positive battery cables get up front to the engine and starter? Are there any junctions (like a steel subframe on the negative side) on either cable that could cause a voltage drop?

[froggy47]

It was mostly the loose nuts on the 2 starter cables. IMO caused by repeated hot cold cycles (cat goes up to 1600f) over 10k miles. I put in a new oem starter & added lock nuts (to provide fore some expansion/contraction capability at the stud connection ) and wrapped cat/starter/pipe with DEI insulation. WEorks 100% perfect hot start, never was battery issue (or cable, or grounds or other)

Link to my videos torubleshooting & fixing it.

https://www.corvetteforum.com/forums...er-videos.html

Thanks llc5