Tuning 1968 Fiat 500L dies when accelerator is pushed

[Nts550]

Hello all,

I have a 1968 Fiat 500L. It’s Spring now and I’m trying to get the 500 out. It’s starts great and idles, but dies when the accelerator is pushed. It will rev higher when carb cleaner is sprayed into the intake, but quickly loses any ability to rev once the carb cleaner is not being sprayed. The car sat for a month at a time over the winter. I used premium gasoline, but just switched to non-ethanol premium and now I have problems. There’s still a half tank of regular premium fuel mixed with premium non ethanol.

Any advise would be great. Should I rebuild the carb?

Thank you

Nate

 

[Bleeding Knuckles]

Hi Nate, modern fuel can can, with time, turn into an unholy mess in the fuel system if not flushing through with clean (new) fuel during use. I would start with the filters at the tank, pump and carb. Check fuel flow when turning over at the carb, and strip and clean the carb. While you are at the pump check the diaphragm is ok.
Ian.

 

[Nts550]

Thank you Ian! I’ll give it a shot and see what happens.

Do you think to poor quality American fuel caused the problem? I did switch to non-ethanol: maybe I switched too late…or maybe the non-ethanol is the problem.

 

[Bleeding Knuckles]

Hi Nate, It is possible the fuel is of low quality, but the tank in the 500 is not good at preserving the contents - it just seems to turn gungy and can block filters, best to keep running things and using the fuel.
Ian.

 

[F30Msport]

Nate, is it time for new spark plugs? I had a similar issue and that solved it.

 

[Nts550]

Prior to leaving Italy, (1 year ago) I took the car in for a full tube up at a classic 500 garage. It is possible the mechanic just cleaned the plugs; even though he said he changed them. It’s a cheap fix. I will give it a shot. Thank you for your advise!!!!

 

[Veloman518]

I run all my vehicles (many are older cars and bikes) on whatever fuel is available and never have major issues. The problem with ethanol isn’t so much the running as it is the sitting. Leaving ethanol fuel in the tank for months will cause it to separate and gum up fuel pumps and carbs. I wouldn’t get too concerned with using it in general. I absolutely top everything off a few times with ethanol free before I hibernate for the winter though.

Carbs on these are pretty simple to disassemble and clean thoroughly. While you’re in there check all the fuel filter screens and the float height for sure. If the float isn’t set right the bowls could be emptying just when the car is calling for more fuel.

 

[Nts550]

I fixed the problem. The non-ethanol fuel caused a lot of the rust inside the old tank to dislodge and clog the fuel system. A new fuel tank, cleaned lines, rebuilt car, rebuilt fuel pump and soda blasted the fuel sender (tube in the tank) solved the problem. I don't drive this car often, so I use only non-ethanol fuel. It starts perfectly and runs great every time.