'75 Spider Won't Start When Hot

[gcorsar]

This one's tough. While adjusting the carb, my Spider started fine when cold, but after it warmed up and I put the air cleaner back on I couldn't start it again. The same thing happened when I first got the car. I started it cold (push started it because the battery was drained and I had to get it home), let it run, and shut it off. When I tried to start it again, no luck.

When it happened the first time I thought it was an electrical problem. I started checking things but gave up because it was about 103 degrees out and I needed a break! I went back about 2 hours later to work on it again, made sure gas was getting to the carb and spark was coming from the coil, turned the key and it started right up. I've started the car a few times since then but always cold so I didn't notice the problem again until I decided to rebuild the carb. Cold engine, starts fine. Hot engine, won't start.

Any ideas?

Thanks!

[Observer]

Check The Thermo Timer switch

[So Cal Mark]

you need to be more specific. Does the starter operate when hot, or is a no-crank situation?

[gcorsar]

@Observer: Thanks, but I'm new to the Fiat world. What's the Thermo Timer switch and where would I find it?

@So Cal Mark: The engine does crank when hot, but it never catches. It sounds like an electrical problem because I don't get any indication that the engine is trying to fire (like sputtering or backfiring). That's why I pulled the coil wire and looked for spark and saw that there was spark. The fuel filter (one installed in the engine bay, not sure if that's OEM or added by a previous owner) has fuel and I can see fuel flowing into the carb if I manually operate the throttle linkage. Does that help?

[So Cal Mark]

yes, it helps. Your car doesn't have a thermo-time switch. Those are only on FI cars. I'd suspect your engine is flooded upon restart. The fuel in the float bowl may be boiling when you shut the engine off hot, or the float level may be incorrect. Get the engine up to operating temp with the air cleaner lid off. Shut off the engine, wait a couple of minutes, then look down the primary venturi. If you see fuel trickling in, you've found the source of the no-start

[gcorsar]

I'll have to give that a try over the weekend. I got new points and condensers too just to clear up any questions about electrical problems.

[gcorsar]

@So Cal Mark: Well I finally had a chance to get back to this thread. It looks like the problem was a multitude of things all working against me. I rebuilt the carb, updated the distributor to a single point configuration, set the dwell, timing, and idle speeds, and things seem to be working much better.

As for your suggestion about fuel in the bowl boiling over, that may have actually been the cause. I decided to rebuild the carb because I noticed fuel leaking around the lower primary butterfly shaft. After the rebuild, no fuel leak.

Thanks for the help!