Hey. My 500 with a 650cc engine is running poorly. It just died the other day while operating fine just moments before. Then wouldn't start again. Skip ahead a few days and she starts right up and seemed to be running well. I drove it home and about 1/4 mile from the house it bogs down and almost dies same as before but it only started to die as I pushed the fuel pedal. I get it home and let it cool down and I get it started but now it runs very poorly. Maybe misfiring or something. I am getting spark at both cylinders. I am trying to figure it out but I'm a little stumped because now when I let off the throttle it dies. Any ideas?

Hi. Have you looked at fuel starvation? Airlock in the tank?

I've had similar issues and tried (still a work in progress) to sort the problem. I've replaced the coil pack and now wrapped the exhausts. I'm going to double wrap it as I think heat is the problem. I've also wrapped the coil. Also going to change my leads. My dad also adjusted the tappets as I was advised they maybe too tight and effecting the running when hot.

Check for air leaks at base of carb either because the carb is loose , poor gaskets or damaged Bakelite spacer.

hodgy18 said:

I've had similar issues and tried (still a work in progress) to sort the problem. I've replaced the coil pack and now wrapped the exhausts. I'm going to double wrap it as I think heat is the problem. I've also wrapped the coil. Also going to change my leads. My dad also adjusted the tappets as I was advised they maybe too tight and effecting the running when hot.

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I would say coil possibly as well from the description of the problem.

I wouldn't wrap the coil though, you are just going to trap the heat inside and not allow it to dissipate. Eventually the insulation internally is going to break down through overheating and cause further issues.

Tony

My theory to wrap the coil is to stop it boiling over with the heat of the exhausts, however with double wrapping them, i may remove coil wrap and try to improve air to it. Before I couldn't touch the coil for being so hot. I read somewhere or maybe someone quoted me that on the earlier 500's the coil was located on the left hand side of the engine bay.

hodgy18 said:

My theory to wrap the coil is to stop it boiling over with the heat of the exhausts, however with double wrapping them, i may remove coil wrap and try to improve air to it. Before I couldn't touch the coil for being so hot. I read somewhere or maybe someone quoted me that on the earlier 500's the coil was located on the left hand side of the engine bay.

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If the coil was that hot then that you couldn't touch it, I don't think that's due to the heat of the exhaust. It would suggests to me that that the insulation inside the coil is starting to breakdown. Can anyone else who has their coil on the right hand side say whether their coil is too hot to touch after the engine has been running for a while?

My 1966 F has the coil on the left hand side of the engine bay. I don't know why Fiat thought it was a good idea to move it?

If I understand your symptoms correctly, it started OK from cold, ran very erratically and was difficult to start hot? This sounds like it is running very rich--have you checked the carb float? If you get a tiny crack in the float it will slowly fill up with fuel to the point that it won't shut off the needle-valve. Take the float out, and give it a gentle shake---you will soon know if it has fuel in it! If it has, chuck it and get a new one.
Check your coil and electrics as well as making sure that there is no air-leak at the base of the car, all items as suggested by other Forum members.

I put in a new coil. I'm going to check the carb for a leak as soon as I get home. And I will follow up with everything else suggested and let you guys know. Thanks for the suggestions.

I couldn't find a leak, and I can't find the workshop manual that covers the carb that comes on the 650 engine so I'm not sure what all is supposed to be.
I did take a video of it running...
https://drive.google.com/open?id=0B5jgFInUJU3KeEZHaVJWVjc0ak0
And smoke coming back out the carb when the vehicle is off and I open up the throttle plate...
https://drive.google.com/open?id=0B5jgFInUJU3KblI0NzhmVXJLM2c
I was thinking maybe bad valve seats? Any clues?

It sounds like the timing is out to me? Which also could explain why you are getting exhaust gases coming through the carb?

What sort of ignition do you have is it standard points and condenser or electronic? If it's a standard distributor it could be the advance weights in the distributor are sticking and not advancing the timing when you rev the engine?

Have you had the rocker cover off and checked (a) tappet clearances; the 500 is renowned for tappets closing up which could be holding a valve open and, (b) that the rockers and pushrods are working the valves correctly. difficult to diagnose from a distance, but I would still put my money on it being a mechanical fault rather than an electrical one.

I watched your 2 videos.
After the 1st one, I was going to suggest either the accelerator pump wasn't working or there was a partial blockage in the idle jet/circuit. (assuming valve clearances and ignition timing are correct).

After the 2nd video, I don't know. The smoke coming from the carb venturi looks like what normally happens when you open the throttle with the engine off but still hot, i.e. the accelerator pump jet squirts some fuel into the carb venture and the heat of the intake vaporises this fuel, causing 'smoke'.

Is the choke engaged (on)?. Looks like it to me but I'm not sure.

Iirc, and assuming I'm not confusing it with another Fiat model, the idle jet is removable from the side of the carb. without any further dismantling.( Look for a brass plug with a large screwdriver slot in it's head.) If so, try removing the idle jet holder, pull out the idle jet from the holder and blow through in all directions. Then refit.

I agree with what others have said about checking valve clearances, ignition timing, air leaks etc., but the above idle jet clean is easy to do.

Edit: As luck would have it, this idle jet cleaning is covered in another current thread 'My 5ino's transatlantic adventure' See post #37, with all due credit to 'turbo500' and 'fiat500' for the info and very clear pics.

Al.

Thank you all for the info. I will do as suggested as soon as I can and get back to you all with the results. Thanks again.

Sounds like a coil that is getting hot or a fuel pump that is tired and can not keep the proper pressure. I would replace both as they are both cheap and easy to replace.
Tom's suggestion of the carb flooding is also a possibility. I would replace the coil and fuel pump and go from there. Also make sure the fuel filter is not blocked and the fuel pick up in the tank is not blocked.

John

Okay, sorry for not replying sooner to those who gave suggestions. I got busy with work and school and didn't have time to work on it myself. So I took it to the mechanic down the road and from what I can gather from trying to translate what he told me in Italian to English was that the condenser on the distributor was broken, and not producing spark as it should. I also had them replace some baskets to fix some oil leaks while it was there. The valve cover/head gaskets replaced, and he fixed the timing issue. It still occasionally wants to die out when I push the accelerator when it's cold out but that is about it. Thank you all for all your help.