Hello everyone. I am the very happy owner of a 1972 500L that I had been driving for about 2 years now with no issues. All of a sudden it started being starved of fuel. It idles fine but when I mash the accelerator quickly it wants to shut off. If I accelerate VERY slowly it will putter on up to higher revs.
First thing I did was change the fuel filter but the same was still happening. I then changed all of the hoses in case one was clogged and even inspected the few metal lines that it has.
I then purchased a new fuel pump but still the same. At this point I am thinking that the carb needs a rebuild. This is where I am needing a sleuth...
it does not have the typical Weber IBM 26 carb. What it does have is a Dellorto FRG 28 carb that when I try to look for a rebuild kit online all I am getting is newer style carbs and even ones for Vespas. The person that I acquired the car from also gave me a 500R Weber 28 IMB carb but when I install that one the car wont run at all because it floods. It appears that at some point someone sheared off the fuel return nipple on the carb but I am not even sure if that nipple would be useful on this car since I don't even see a return line on the fuel tank. I don't know where else to look. I am going thru Fiat driving withdraws. Any help or advise is welcome. Thanks in advance

After much searching...I finally found a rebuild kit and what this carb went to. Here is some info in case anyone else ever runs into this.
The Dellorto FRG 28 fits the Fiat 126 and it appears that it is for an Abarth version.

Hi Alex I had this problem years ago. It ticks over fine and then it justs builds up the revs really, really slowly. I am pretty sure but can't remember 100% that it was nothing to do with the carb, as you would think and was the tappet gaps causing it.

Tony

Further thinking I am convinced it isn't the carb at all but I am happy to be proven wrong.

I am sure it was ignition related, I would check tappets, points gap etc. Condensor is another favourite that will give these symptoms.

Thanks for the input. I removed the carb and tore it down completely.
Since I don't have new gasket set or a rebuild kit I had to be very careful. I sprayed the entire thing down with throttle body and carb cleaner. Everything looked pretty good except for a little o ring. At the top of the carb where the fuel is brought into the carb is a little cap that's held in by a screw. I removed this and saw grooves had been made into the rubber. I guess from it being under pressure. I removed it and saw that the other side didn't have the grooves. I flipped it over and reassembled everything. Guess what? Darn thing runs great now. Not sure if it was the cleaning or the rubber but you know how it goes a bad rubber can change everything.