Engine won't turn over when warm

[scottfab]

Originally Posted by Paul Workman

However, in retrospect, the problem with the arching is simply moved from the switch to the (mechanical) relay. So! I think I'll re-design the circuit and put a MIL spec solid state (FET) in place of the relay (read: no arching ever).

Not a bad idea as long as the FET is clamped with a zener to protect it from the inductive kick of the starter solenoid. (similar to class D amps).
Then, like any mods, it's a matter of documenting it well and in a place you'll find it if something goes wrong down the road. (or for the next owner) One of the biggest lessons I learned on custom mods was to document well. There's no amount of "oh I'll remember what I did here" that works

Originally Posted by Paul Workman

That said, Marc Haibeck made the comment once that he bypassed the clutch switch because pressing on the clutch puts a good deal of force on the thrust bearing in the LT5, a bearing that can be very dry, depending on how long it has been between startups. So... There's that to consider.

There will always be this pressure on the thrust bearing either before start or after. Failure will not be due to pressure on the bearing but the spin of the bearing dry which would happen regardless. (IMHO)

Originally Posted by Paul Workman

This discussion is warming to a tech article for the Registry, methinks!! But, in the mean time, I agree - we should be a smashin' da clutch afore turnin da key, doanchaknow!!

P.

Best overall solution would have been in the initial design. That is the NO (normally open) clutch switch in line with the high current starter solenoid is bad. Better would have been a NC switch in the gear lever at neutral. No one would be moving it while turning the key.

A noted and well know author and owner of a ZR-1 once said of the GM designers, "these are highly skilled, highly paid engineers that focused on these designs for years. They know more than shade tree mechanics." (paraphrased) That statement comes to me every time is see someone on this forum struggle with some of the more notorious failures. Fact is we've had decades now of experience that those engineers did not have. Improvements are not only needed but necessary for the good of the car. However, I've always made my mods "backoutable" just incase it's important to the next owner. (very likely after I'm gone)