Hot hot hot! No start..

[mplsspider]

Hey gurus, I have a bone stock 1971 that I am having hard/not starting issues with when hot. Here's what I'm experiencing:

Car has always started as expected when cold. I've noticed during past summers (we live in MN) that on warmer days sometimes it would be a bit difficult to start once warmed up and making a stop somewhere, but it would always fire up after a bit of cranking.

Today on first real drive of the year, it's +90F. I had repeated issues not being able to start the car when I'd stopped after driving for a while. In all cases I was eventually able to get her to fire and run (excellently) after a period of waiting, 20m - 40m, and a LOT of cranking. I did notice with experiments that no gas pedal maybe worked better than applying gas.

Having done some research on this forum and others, I'm wondering if I should be chasing down a fuel delivery issue or a spark issue. I had an inboard boat which experienced similar and it turned out to be an electrical spark issue introduced from heat....

Anyway curious if anyone has suggestions on which to start with.

Thanks!
dug

[njoconnor]

No guru, here, but this is from NOV 2015, after 3 years of dealing with that hot start issue:

"It was pouring yesterday, so I fell to work on installing the 14 mm spacer/gaskets (and while hood was up, reconnected the crankcase vent tubes). Just finished this morning, and I'm about to take the car on a test run to the library.

Anywho, most of you will recall one of my first posts was about hard starting issues. This issue plagued us off and on, usually when the weather was hot, the drive kinda short, and the waiting period between starts even shorter (think hot parking lot and a 10 minute dash into the store). One of the replies last summer suggested a spacer, to thermally decouple the carb (and float bowl) from the heat of the engine. As I was removing the air cleaner yesterday, I noticed the carb....moved. Once the cleaner was off, I discovered that all 4 carb nuts were so loose I could turn them with the edge of my index finger! And, considering the location of the nuts, I could sorta understand why: only one of them is easily reachable, and the rest are major PITA's to access with even 1/4 inch drive sockets and short wrenches. Lots of patient tweaking and small movements eventually got the nuts off, new carb studs and spacer installed, and carb tightened back down. Fired up immediately, with none of the stumble I'd become accustomed to. So, recommendation: for anyone who just acquired a carbed 124 from a PO, and there's starting/ running issues, check to make sure the carb is bolted down tight! Yeah, no duh, but who'd a thunk?? All you experienced Fiatistas already have correctly tightened carbs....

In case anyone else is considering the 14 mm spacer, you will need metric studs in the size of 8mm-1.25 pitch x 50mm. These "just fit", but the longer 60mm's come too close to the carb body to allow one to tighten the nuts.

Next project: fuel pump, followed by H-4's and relays. Followed (maybe) by 95amp alternator if the budget allows....."

Almost three years later, we've had zero hot start issues. I credit, in order: 1) the spacer; 2) proper torqueing of the carb on its studs; 3) correcting the carb fuel/air mixtures (per Brad A's recc's); 4) the gear reduction starter.

We're doing heat records in Madison these days, so I'll be "testing" the changes once again. Nice to not have to park on a slope for roll assisted starts anymore.....

Neil

[seabeelt]

Neil, Funny you should post this. This year I have been having the very same problem with our 71 - though I'm running dual IDFs on a waffle manifold. Never had a problem until this year - left me stranded at a Wendy's but stated right up the next morning. HMMMMMMMMM. I will go back and check the carb bolts. yes PIA to tighten. I went from the standard fuel pump to the blue holley electric pump in the trunk and have the pressure adjusted to 3 psi at WOT as I thought that fuel delivery might be the problem..... Thought I solved the problem but it happened again last week. (don't really care for the pump as its noisy and I never really had a problem with the standard mechanical pump - don't like it in the trunk either)

[Zoofly]

I had this problem. The connection at the "temperature gauge sending unit" was loose. I fixed that and the problem went away. Here's a link to locate the sending unit.

https://www.youtube.com/watch?v=8DtcIlkt4BY

Hope that helps.

[seabeelt]

Well I finally solved the problem. Turns out it had nothing to do with the carbs at all. Darned ballast resistor was heating up and creating so much impedance that I had no spark . Go figure. Haven’t decided whether to put the original fuel pump back on or live with the hum of the electric one in the trunk for a while longer as I like the way it primes the carb if it’s been sitting a while.