Technical 68 500L won't start hot

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Technical 68 500L won't start hot

DsailsHRrs

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Hi - I know there are other threads on this and I've been reading them. I'm trying to determine if my issue is carb or solenoid so I did an experiment with an infrared thermometer. My issue is when the car is hot and I shut it off it will start immediately (not great but starts). If I let it sit for a few minutes it won't start until it cools down again. (this car starts on barely a crank when cold - I'm actually always surprised how fast)

So I took some temperatures while idling and then took some after it sat for 5 - 10 minutes and wouldn't start. Here is what I found:

(temps in fahrenheit)
fuel line - idle 117 after 5 minutes 151
carb bowl - idle 155 after 5 minutes 154
base of carb - idle 159 after 5 minutes 182
solenoid - idle 157 after 5 minutes 123

I tried to get parts of the engine/manifold and it seemed around 200

It makes sense that some things are cooling and some are getting hotter because the fan is no longer working.

Anyone have thoughts on what I should chase down to solve my issue?

Don
 
Have you checked your valve clearances? They may be set too tight and that will present problems when the engine is hot, such as low compression. The wrong clearance will adversely affect the valve timing. Low compression means it will be difficult to start or may not start at all. The rise in temperature once the engine is switched off may be enough to prevent the car from restarting. Tight valve clearances is a common problem on the Fiat 500.

If the car cranks over well it's not a solenoid or starter problem. The temperatures that you've quoted don't seem excessive so I don't think that fuel vaporisation is a problem.

I would check valve clearances and the ignition system before moving on to the fuel system.
 
Thanks for the response. Valve clearances weren't on my list for this issue but it was on my list of things for the future. I'll move that up, do it now and see if it helps.
 
Thanks for the response. Valve clearances weren't on my list for this issue but it was on my list of things for the future. I'll move that up, do it now and see if it helps.
Curious if you checked your clearances and if so did it sort out your issue? I've had similar issues, but not yet give the car a good run to try it
 
I haven't had a chance to yet - decided to order a new gasket first (I'll most likely need it) I will post the result when I do this
 
So I did the valve adjustment. It was badly needed and the valves were definitely too tight as Hobo1960 suggested.

Unfortunately it didn't solve my problem.

It did make a difference in performance, so a worthwhile task. I was also very hopeful because when I first turned it off hot and restarted, it did great - perfect actually (much better than before). But when I let it sit for 10 minutes it refused to start until it cooled down again. It takes about half an hour until it will restart.

Frustrating!
 
Have you checked to see that you're getting a good spark at the plugs when you're trying to restart the hot engine?

If the coil or condenser is breaking down when it's hot, there may be a good enough spark to keep a running engine running, but not enough to restart the engine. This is because the voltage reaching the ignition coil will be less with the starter motor cranking, so the spark will be even weaker. This is why many manufacturers adopted a ballasted ignition system. I'd check the ignition system before moving onto the fuel system.
 
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