Technical Starts from cold runs until warm then dies

[Tinyotim]

I’m struggling to get our little fiat running at the moment, it’s had a cutting out at junctions
issue for a while now which has gradually gotten worse , I took it for Arun on Sunday and ended up being towed back home.
It seems to start well from cold and run like a champ until warmed up , then when it’s warm it dies as soon as the accelerator is touched.
I have fitted the electronic ignition module and a new coil and plugs , stripped and cleaned the carb etc new fuel filter .
I’m thinking now about the fuel pump?
Would it work until hot then not ?
Is this a possibility? Any advice gratefully accepted

 

[dragonwagon]

I’m struggling to get our little fiat running at the moment, it’s had a cutting out at junctions
issue for a while now which has gradually gotten worse , I took it for Arun on Sunday and ended up being towed back home.
It seems to start well from cold and run like a champ until warmed up , then when it’s warm it dies as soon as the accelerator is touched.
I have fitted the electronic ignition module and a new coil and plugs , stripped and cleaned the carb etc new fuel filter .
I’m thinking now about the fuel pump?
Would it work until hot then not ?
Is this a possibility? Any advice gratefully accepted

That sounds like a fuel vapourisation issue or an air leak at the carb flange. Worth checking.

 

[Tinyotim]

That sounds like a fuel vapourisation issue or an air leak at the carb flange. Worth checking.

I’ll check it thanks

 

[the hobbler]

I’ll check it thanks

Due to people over-tightening the carb flange nuts, it is not unknown for both the bakelite spacer AND the flange on the carb to warp. These need to be flattened---"wet 'n dry" ( and used 'wet' with WD40 or similar) on a totallyflat surface. A piece of thick glass is perfect if a steel 'flat' is not available.
Have you tried running the car with the choke 'on' slightly? if you do, and that keeps the engine running, than it means that the engine is running lean---too much air.

 

[Sbf500]

Due to people over-tightening the carb flange nuts, it is not unknown for both the bakelite spacer AND the flange on the carb to warp. These need to be flattened---"wet 'n dry" ( and used 'wet' with WD40 or similar) on a totallyflat surface. A piece of thick glass is perfect if a steel 'flat' is not available.
Have you tried running the car with the choke 'on' slightly? if you do, and that keeps the engine running, than it means that the engine is running lean---too much air.

This is exactly what happened to mine, did the above using a plate of glass and some wet and dry and problem solved.

 

[Tinyotim]

So , after trying all of the above suggestions and all of the following I'm starting to despair
- Fitting new coil
- Replacing points with electronic ignition
-cleaning and rebuilding carb with rebuild kit , then spraying for leaks with WD etc
-Checking valve timing
- Checking ignition timing
-Fitting new Fuel pump new fuel filter
-replacing fuel line front to back
- removing fuel filter from inside tank and checking (its all new and clean)
- New Spark plugs

I have exactly the same issue as before (probably worse now , car will start just fine on choke , run on idle until warmed up then die as soon as I try and move away.
If I leave it to cool for 10 mins it will start again even without the choke but then die when warmed up as before .
At my wits end with it now as I'm usually pretty good with this sort of stuff but I seem to have completely run out of ideas now .

Any advice gratefully accepted

 

[the hobbler]

So , after trying all of the above suggestions and all of the following I'm starting to despair
- Fitting new coil
- Replacing points with electronic ignition
-cleaning and rebuilding carb with rebuild kit , then spraying for leaks with WD etc
-Checking valve timing
- Checking ignition timing
-Fitting new Fuel pump new fuel filter
-replacing fuel line front to back
- removing fuel filter from inside tank and checking (its all new and clean)
- New Spark plugs

I have exactly the same issue as before (probably worse now , car will start just fine on choke , run on idle until warmed up then die as soon as I try and move away.
If I leave it to cool for 10 mins it will start again even without the choke but then die when warmed up as before .
At my wits end with it now as I'm usually pretty good with this sort of stuff but I seem to have completely run out of ideas now .

Any advice gratefully accepted

Sad to say, this sounds like the scenario for a duff ignition pack, and I read that you have fitted a new one. Do you still have all the parts to re-instate the 'points' ignition? Worthwhile to try that, along with a 'Swiftune' condenser, mounted up by the coil. I work in a 'classic car' garage, and it is not unknown for new ignition packs to 'pack up' (sorry for the pun) after being used for a very short time. Might be worthwhile sending it back to the supplier for a warranty exchange. Lastly, check that the ignition pack has been wired up correctly---even experienced mechanics can get it wrong (but don't tease my boss about that!). The Fiat is NEGATIVE earth.

 

[Tinyotim]

Sad to say, this sounds like the scenario for a duff ignition pack, and I read that you have fitted a new one. Do you still have all the parts to re-instate the 'points' ignition? Worthwhile to try that, along with a 'Swiftune' condenser, mounted up by the coil. I work in a 'classic car' garage, and it is not unknown for new ignition packs to 'pack up' (sorry for the pun) after being used for a very short time. Might be worthwhile sending it back to the supplier for a warranty exchange. Lastly, check that the ignition pack has been wired up correctly---even experienced mechanics can get it wrong (but don't tease my boss about that!). The Fiat is NEGATIVE earth.

Thanks for your reply, I’ll be trying the points again, but I only changed out the points for electronic ignition in order to solve the same issue I’m having now in the first place.
So it would be a big co-incidence to end up with the same issue as before.
As said earlier im getting desperate now so I will try what you suggest.
Thanks

 

[Sbf500]

Does it fail on one cylinder first or both at the same time? Mine would always start to die on one first before both failing so at first I though it was ignition related but then when you pulled a lead on the not failing cylinder the other started working again and it would run roughly on that one cylinder. Plus I had a spark on both when it failed. Mine was a combination of a warped carb base, which only showed up a real sizable leak when hot which made sense with it being a heat related issue. Also the carb base was missing the drain tube with the crimp in the end so that was causing a bigger air leak as well so a new base and sanding flat the carb base sorted my issue out. Unfortunately it took me 10 years to figure it out. I had replaced pretty much every thing else, a rewire, voltage regulator, distributor, whole ignition, fuel pump, fuel lines, sender unit, head off checked the valves........the list goes on. Had the car not had so much sentimental value I would have given up ages ago but glad I stuck with it as it is working like a dream at the moment.

Just make sure you do one thing at a time as for me there would easily have been times when I changed so many parts that I wouldn't have know if a certain thing fixed the problem.

 

[Tinyotim]

Does it fail on one cylinder first or both at the same time? Mine would always start to die on one first before both failing so at first I though it was ignition related but then when you pulled a lead on the not failing cylinder the other started working again and it would run roughly on that one cylinder. Plus I had a spark on both when it failed. Mine was a combination of a warped carb base, which only showed up a real sizable leak when hot which made sense with it being a heat related issue. Also the carb base was missing the drain tube with the crimp in the end so that was causing a bigger air leak as well so a new base and sanding flat the carb base sorted my issue out. Unfortunately it took me 10 years to figure it out. I had replaced pretty much every thing else, a rewire, voltage regulator, distributor, whole ignition, fuel pump, fuel lines, sender unit, head off checked the valves........the list goes on. Had the car not had so much sentimental value I would have given up ages ago but glad I stuck with it as it is working like a dream at the moment.

Just make sure you do one thing at a time as for me there would easily have been times when I changed so many parts that I wouldn't have know if a certain thing fixed the problem.

That’s interesting, I’ve not heard of the drain tube on the carb base before and I certainly didn’t see one when I took the carb off .
Is this something common to all years /engines ?
As for the leaky base , mines flat and I’ve squirted it more than once when hot so I’m pretty confident I can rule that out .
Thanks for the suggestions

 

[Sbf500]

That’s interesting, I’ve not heard of the drain tube on the carb base before and I certainly didn’t see one when I took the carb off .
Is this something common to all years /engines ?
As for the leaky base , mines flat and I’ve squirted it more than once when hot so I’m pretty confident I can rule that out .
Thanks for the suggestions

So if you are running the standard 499cc engine with the 26 IMB carb (not sure about the R) there should be a little tube poking out the side of the base https://www.ricambio.co.uk/carburettor-carb-spacer-drip-tray-classic-fiat-500 like this one. If the tube is missing the whole will be bigger as the end is crimped and thus you will be unknowingly running a leaner mix.

 

[The Mouse That Roars]

How frustrating, how can a car so simple be such a problem, something we’ve all probably asked ourselves at some point.
I‘ve just had the problem of the missing drain tube from the carb base, it had always been a bit loose but on the last trip out it fell out. Symptoms, engine would stall the moment I was off the throttle, the most amazing “chuff” noise on over run and with the engine cover opened a huge sucking noise!
Unbelievably the missing tube was still in the bottom of the engine compartment, thinking I would just glue it back in I removed the plate only to discover it was cracked and slightly damaged, so a new one ordered.
On fitting the new one problems occurred with the fit of the gasket and the plate fouling on the head stud washer, this had caused the damage and the crack on the original ( this damage and crack wouldn‘t affect the running as the gasket doesn’t seal the head stud recess from the inlet)
All reinstalled and Luigi is back to running like a Swiss watch!
As for your problem with the car cutting out when hot, Luigi did the same after I had rebuilt the engine. It would start and run fine then cut out and not restart, let it cool down it would then restart run fine until warm then cut out again. In my case it was caused by valve clearance.
Stick with it the answer is in there somewhere!

 

[Tinyotim]

My R Has the 28 IMB , ive looked at the base and the new ones on sale and they don't have the tube so at least I can rule that out now.
Once ive changed back to points and eliminated the ignition being at fault ill check the valve clearances again just in case.

 

[Sbf500]

My R Has the 28 IMB , ive looked at the base and the new ones on sale and they don't have the tube so at least I can rule that out now.
Once ive changed back to points and eliminated the ignition being at fault ill check the valve clearances again just in case.

The hard thing seems to be there are a number of faults that seem to present very similar issues. Keep at it and i'm sure you will get there!

 

[matt1267]

I’m struggling to get our little fiat running at the moment, it’s had a cutting out at junctions
issue for a while now which has gradually gotten worse , I took it for Arun on Sunday and ended up being towed back home.
It seems to start well from cold and run like a champ until warmed up , then when it’s warm it dies as soon as the accelerator is touched.
I have fitted the electronic ignition module and a new coil and plugs , stripped and cleaned the carb etc new fuel filter .
I’m thinking now about the fuel pump?
Would it work until hot then not ?
Is this a possibility? Any advice gratefully accepted

Hi. Did you ever get your stalling sorted out? Just reading forums and iv got a similar problem. Doing my head in!!

 

[Tinyotim]

Hi. Did you ever get your stalling sorted out? Just reading forums and iv got a similar problem. Doing my head in!!

Hi , Yes after I had swapped almost everything connected with the ignition side and the fuel (carb , pipes etc) to no avail I bought and fitted a reconditioned distributor .
Problem solved .

 

[heggae]

I had a similar problem on a saab model 96. I also have a Fiat 500 vintage so I don’t know if the carburetor had some similarities, but I turned a screw at the base with the carburetor(not a mixture screw) which changed the float level on the saab carb and that problem disappeared.