Technical Fiat 500L 1968 stalls when engine is warm

[Ian Glaude]

Hi all,

With my Fiat 500L from 1968 I’m encountering the following problem:

When the engine get’s hot (after approx. 30 mins) the Fiat stalls at traffic lights or junctions. When stalled, the Fiat does not start right away. If I want to start it again, I have to let it cool down for 10-15 minutes, then it runs fine again until the engine gets hot again…

I tried adjusting the valves to the correct timing. This did not help.

Does someone know what this problem is and how to tackle it? I was thinking of fuel vaporization, but I am not sure…

Thanks

- Ian

 

[bugsymike]

Hi all,

With my Fiat 500L from 1968 I’m encountering the following problem:

When the engine get’s hot (after approx. 30 mins) the Fiat stalls at traffic lights or junctions. When stalled, the Fiat does not start right away. If I want to start it again, I have to let it cool down for 10-15 minutes, then it runs fine again until the engine gets hot again…

I tried adjusting the valves to the correct timing. This did not help.

Does someone know what this problem is and how to tackle it? I was thinking of fuel vaporization, but I am not sure…

Thanks

- Ian

If worse in hot weather then you could be right about fuel vapourisation.
Two things,do you have an insulator fibre block between carb and manifold which if left out may cause issue with heat transfer.
The other thing is if fuel line or after market fuel filter is getting too hot in engine compartment, it can aggravate a problem.
Modern cars have a flow and return system which helps keep fuel cooler.
Another solution seen on VW Beetles is the boot/engine lid fixed in a slightly open position to aid heat dispersal.
Others on Forum are more familiar with specific Fiat 500 issues, my knowledge is 55 years general motor trade

 

[Ian Glaude]

If worse in hot weather then you could be right about fuel vapourisation.
Two things,do you have an insulator fibre block between carb and manifold which if left out may cause issue with heat transfer.
The other thing is if fuel line or after market fuel filter is getting too hot in engine compartment, it can aggravate a problem.
Modern cars have a flow and return system which helps keep fuel cooler.
Another solution seen on VW Beetles is the boot/engine lid fixed in a slightly open position to aid heat dispersal.
Others on Forum are more familiar with specific Fiat 500 issues, my knowledge is 55 years general motor trade

If worse in hot weather then you could be right about fuel vapourisation.
Two things,do you have an insulator fibre block between carb and manifold which if left out may cause issue with heat transfer.
The other thing is if fuel line or after market fuel filter is getting too hot in engine compartment, it can aggravate a problem.
Modern cars have a flow and return system which helps keep fuel cooler.
Another solution seen on VW Beetles is the boot/engine lid fixed in a slightly open position to aid heat dispersal.
Others on Forum are more familiar with specific Fiat 500 issues, my knowledge is 55 years general motor trade

Thank you! I will check it!

 

[Goldnrust]

Does the car run well when hot otherwise? And it's just the idling where it's struggling?

Apologies if this is massively patronising, but when restarting it, have you got your foot on the accelerator? The original handbook suggests you might need to give the car full throttle while trying to restart it when hot.

If it's just a problem at idle, it could be as simple as the idle mixture being set too rich. You could try winding the idle screw in al the way and count the turns. In a standard engine that's running well you'd expect it to be between 1-3 turns out for a nice idle.

If the car is generally running poorly when hot, another thing to consider is the coil. The coil gets the full blast of the hot air coming off the engine and this heat can cause some coils to fail, but it wont show up when the car is cold.

 

[Ian Glaude]

Does the car run well when hot otherwise? And it's just the idling where it's struggling?

Apologies if this is massively patronising, but when restarting it, have you got your foot on the accelerator? The original handbook suggests you might need to give the car full throttle while trying to restart it when hot.

If it's just a problem at idle, it could be as simple as the idle mixture being set too rich. You could try winding the idle screw in al the way and count the turns. In a standard engine that's running well you'd expect it to be between 1-3 turns out for a nice idle.

If the car is generally running poorly when hot, another thing to consider is the coil. The coil gets the full blast of the hot air coming off the engine and this heat can cause some coils to fail, but it wont show up when the car is cold.

When I keep driving there is no problem… the problem appears when I need to make a stop (ex. traffic light or junction). Then it starts struggling…

That’s why I think it is fuel vaporization…

 

[Ian Glaude]

When I keep driving there is no problem… the problem appears when I need to make a stop (ex. traffic light or junction). Then it starts struggling…

That’s why I think it is fuel vaporization…

Idle screw wasn’t the issue…

 

[bugsymike]

When I keep driving there is no problem… the problem appears when I need to make a stop (ex. traffic light or junction). Then it starts struggling…

That’s why I think it is fuel vaporization…

Does sound quite feasible as temp would rise when stationary with less fuel moving through the pipes.

 

[the hobbler]

Does sound quite feasible as temp would rise when stationary with less fuel moving through the pipes.

It does sound like a mixture problem---just before it gets to the temperature that it stalls at, it could be well worth while checking, and adjusting as required, the idle MIXTURE, as well as the idle speed. It is also possible that the idle jet has some muck in it. If you have a standard Weber IMB carb, the idle jet is on the engine side of the carb (looking from the rear of the car) just under the carb's top-cover plate. You will need a 'flat' screwdriver to take the jet-holder out---the jet pushes into the end of the jet-holder.

 

[Ian Glaude]

It does sound like a mixture problem---just before it gets to the temperature that it stalls at, it could be well worth while checking, and adjusting as required, the idle MIXTURE, as well as the idle speed. It is also possible that the idle jet has some muck in it. If you have a standard Weber IMB carb, the idle jet is on the engine side of the carb (looking from the rear of the car) just under the carb's top-cover plate. You will need a 'flat' screwdriver to take the jet-holder out---the jet pushes into the end of the jet-holder

Thank you.

I will check this.

 

[lazylobster]

I had this. bad spark plug that broke down when it got hot. I would get a multimeter on the coil to confirm it's good readings when cold and also when it's hot.

I would get the meter on the spark leads as well, measure the resistance. If high, replace.

I replaced the lot, coil, plugs and leads, been great ever since.
R

 

[Ian Glaude]

I took my carburator off and saw it was not flat….

This could also be the problem right?
I uploaded it to youtube for you all to see:

 

[heggae]

How interesting. Thank. How do you think that happened. ? Did you just file it down.

 

[bugsymike]

I took my carburator off and saw it was not flat….

This could also be the problem right?
I uploaded it to youtube for you all to see:

Ha,ha, probably not helping.
Looks like someone over tightened it at some time.

 

[Toshi 975]

The 500 Weber 26IMB carbs are notorious for having warped flanges where they have been mistreated over the years causing rocking and or air leaks. The flange is weakened by the hole for the idle mixture screw. You need a good Bakelite spacer and gaskets. The flange can be straightened mechanically if you are brave or flattened on a sheet of wet or dry on a flat surface.

 

[Ian Glaude]

The 500 Weber 26IMB carbs are notorious for having warped flanges where they have been mistreated over the years causing rocking and or air leaks. The flange is weakened by the hole for the idle mixture screw. You need a good Bakelite spacer and gaskets. The flange can be straightened mechanically if you are brave or flattened on a sheet of wet or dry on a flat surface.

I will try to flatten it shown in the video above.

Is this the cause of the problems?