Technical 1966 500F Runs But Dies - Need Advice

[AutobianchiGuy]

I'm hoping one of you seasoned Fiat 500F owners can help me. I have a 1967 Autobianchi Bianchina with a 499cc Fiat 500F engine. My problem just started a couple weeks ago. After putting in electronic ignition and getting it all dialed in it was purring like a kitten (a loud kitten). Then a minor disaster struck. While out for a spin the engine started sputtering and I lost power. Had to pull over to the side. Now I can start it up and it runs fine until I start driving along and then it just loses power and dies. It has fresh gas and it seems to be getting fuel just fine but I can't get it past second gear without a total loss of power. I am able to limp back home to get it in the garage but only slowly and people seem very willing to give me a friendly one finger wave for slowing them down so much. Any guesses on what I should do?

 

[ianhunterv8]

Not that I am any kind of expert in dying Fiat 500s, having got one myself, but try taking off the fuel tank cap when it dies and see if you have created a vacuum - you can hear air rushing in if you have.

That means a blocked breather or the wrong fuel cap. Your symptoms match exactly!

Happenned to me!

Best regards

Ian

 

[Damon500]

My guess would be a possible blocked main jet in the carburettor- undo the 10mm brass plug on the airfilter side of the float chamber at the base of the carburettor (beware- fuel will come out) then unscrew the jet from the holder and see if there is any debris in the jet or holder- often there will be a small piece of dirt blocking the jet and causing the problems you describe.
Good Luck!

 

[Toshi 975]

Might be worth checking for air leaks at the base of the carb, carb could be a little loose, mounting flange could be bowed, damaged gaskets or crack in carb spacer. Do not overtighten carb though as you may cause some of these problems. Pretty much every Weber 26IMB carb I have rebuilt had a bowed flange.

 

[AutobianchiGuy]

I tried loosening the gas cap and was hoping that would solve the problem. It really sounded like a vacuum situation was happening. Sadly, I'll have to dig deeper. I did notice, however, that the pulley on my alternator is really warped and the belt is now super loose. That couldn't have anything to do with it, could it?

 

[johnkeech]

I have a 1961 that is doing the same thing you describe, what did you determine was the problem?

 

[Toshi 975]

I had exactly the same thing on my newly rebuilt engine a couple of weeks back. Engine would start and tick over fine but very little power and no revs. Suspected fuel starvation so checked for air leaks at base of carb and that main jet was ok. Then total carb strip and clean. Still had the problem so tried changing the coil and it has been fine since. The engine is a 650 with some tuning so revving quite well which must have been too much for the coil as it went all of a sudden. I did wonder if the electronic ignition was causing the coil to run hot but I had lashed on the new coil with the old one still in place and after a run they were both quite hot purely due to the heat from the exhaust in the engine bay.