Won't Crank when Hot

[felo72]

Hi all, been working on a 75 124 Spider and chasing gremlins. Rebuilt the carb, new radiator, new alternator, intake and exhaust manifold gaskets, replaced multiple coolant and vacuum hoses, checked ignition timing and cam belt timing, removed air pump, plugged air pump hose at intake, but EGR hose is still hooked up to feed the air filter... She starts up and runs like a champ now, however after going for a ride and at operating temp, if I turn it off and then come back to turn it back on, it won't even crank over. I've had the battery tested and it checks out fine. If I let it sit for a couple hours it'll fire right up like nothing was wrong. I'm guessing it's the starter, but I've read how much of a pain that job is to do. Hoping there are other issues I could check before diving into that job. Thanks in advance!

[18Fiatsandcounting]

Does the starter motor "click" at all when you turn the key? Try starting when hot with the headlights on and see if they dim when the key is turned to start.

I can think of 4 things that cause the starter motor to do nothing when you turn the key to start:
1) Failing ignition switch
2) Poor connection at the 3 wire connector going to the starter motor, the one with brown/black/red wires.
3) Failing starter solenoid
4) Bad connections at the battery, ground posts, or the large red wire that goes to the starter solenoid.

Bryan

[felo72]

Thanks Bryan. The starter does not click at all when I turn the key, when hot. The headlights do dim when I turn the key and the radio shuts off. I've cleaned the battery terminals and charged the battery several times.

[18Fiatsandcounting]

OK, that means the starter motor is trying to draw power. What I suggest checking next is the ground strap from the bellhousing of the transmission to the body underside of the transmission tunnel. It's actually kinda common for that to be missing or loose or otherwise not grounding the engine to the body.

If you think about it, without this ground strap, there is almost no grounding pathway for the engine block. All the hoses to it are (non-conductive) rubber, it sits on rubber engine mounts, and the exhaust system is often hanging only by rubber straps. All that leaves to ground the engine are the accelerator and clutch cables, which really don't like it when 200 amps tries to flow through them...

-Bryan