General Fiat 500L - Engine not idling

[bellucci]

This thread has reminded me that last year an owner of a car fitted with a 650 engine and running a 28IMB carb had trouble trying to get it running properly after he rebuilt the carb. As a last straw he sent the carb to me to have a look at. He had got a rebuild kit from a well known UK supplier which I found to be pretty poor quality. The main gasket was about half the thickness of the originals but worse it had that shorter fuel inlet valve insert which made it impossible to adjust the float properly. I re-rebuilt the carb using parts I was happy with and all was well

Exactly!! I'm glad I'm not the only one who has experienced this. I cannot get two parts that are consistent with one another. It's such a hit and miss. I went through 4 different repair kits from 4 different vendors (Italy, Germany, UK and here in USA) all because the gaskets were poor quality. Just for giggles, these are all the gaskets I went through until I found the right thickness. I even ended up making one myself. While I was so focused on the gasket inconsistencies, I did not pay attention to the other parts until now.

 

[bellucci]

The taper on the needle from the kit is also concerning. Look at the massive difference between the 2. the angle might be the same, but the overall length of the taper (the new one being much shorter), might prevent the needle from fully sealing off fuel flow (needle body bottoming out in seat). One thing you can do/test... when you have the float attached to the top half of the carb, flip the top half over so the float is closed from gravity, and try and blow into the carb fuel inlet (block off the return barb with your hand), and see if its fully sealing and not letting any air thru.

On avg, fuel pressure is around 2-4psi, we can only blow about ~1psi, so it should easily seal shut against human breath.

Great idea. I'm in the process of reassembling so I'll test it out using the old needle.

 

[bellucci]

Hi everyone, I know this is a few months late, but I wanted to thank everyone for their help. I was able to get my Fiat up and running and wanted to share what happened in case it's of any use to anyone.

After changing the parts in my carburetor with the correct ones, I found out that my engine was heavily flooded due to the carb leaking gas as a result of using the wrong needle. This explained the heavy black smoke every time I tried to turn it on. It also explained why it was running so rich. I changed its oil, added double gaskets between the carb and the engine and in between the carb and the manifold. That sealed everything so there wouldn't be any gas and air leakage.

I also decided to leave the choke down especially when starting the car since where I live where it's 80 degrees and humid. This tip also helped me a lot! After all this, I started the engine, and it started without any help. The RPM is a bit high, but the engine runs without losing power or turning off. Now I can start tuning it and lower the RPM.

Lesson learned is, don't just swap out carb parts. Buy from a reputable dealer, buy quality parts and make sure you keep the original parts of your carb so you have a point of reference.

Thanks again everyone for all your help.