Technical '72 500L Refuses to Start

[criceo]

After an engine rebuild my 500L lived for about an hour. First problem arose when she failed to do above 50 mph, when 55-60 mph was achievable before. Then, a sudden loss of power and an inability to do above 35mph. Now, she refuses to start. She'll crank, and, if I apply the throttle, she'll sputter as though she's about to start. However, no amount of time of this sputtering will lead to life. Good spark, proper timing, good compression, and extra fuel being delivered to the engine, but no dice. Carb is being stripped ATM, though it was just purchased from Pierce Manifolds to replace the old one during the rebuild.

Any thoughts on the matter? This one is a real head scratcher! I'd love any suggestions, as this sweet little car has been off the road for far too long!

 

[Toshi 975]

What was the replacement carb?

 

[criceo]

A Weber 26 IMB, same as the one that it was a replacement for.

 

[fiat500]

After an engine rebuild my 500L lived for about an hour. First problem arose when she failed to do above 50 mph, when 55-60 mph was achievable before. Then, a sudden loss of power and an inability to do above 35mph. Now, she refuses to start. She'll crank, and, if I apply the throttle, she'll sputter as though she's about to start. However, no amount of time of this sputtering will lead to life. Good spark, proper timing, good compression, and extra fuel being delivered to the engine, but no dice. Carb is being stripped ATM, though it was just purchased from Pierce Manifolds to replace the old one during the rebuild.

Any thoughts on the matter? This one is a real head scratcher! I'd love any suggestions, as this sweet little car has been off the road for far too long!

It sounds a bit hard on a rebuilt Fiat 500 engine to be expecting the performance you mention within the first hour after a ull rebuild. I know you're not meant to mollycoddle a new engine, but even 50mph might be harsh within the first hour.

Was it rebored and re-shelled or a more minor overhaul. It is possible that it was a bit tight after the rebuild and has got a bit tighter through heat. Can you turn it easily by hand on the pulley?

 

[dangfiat]

I feel for you. I just bought a 500F at auction and the motor will start, but won't rev. I have the carb off for a clean/rebuild to see what happens.

Timing is correct, valve backlash is correct. Just seems to be getting starved of fuel. The next step is to replace fuel lines, then sender/filer and finally the tank itself

Finicky little beasts these 500's. But for some reason you just have to keep trying!

Other than look to the fueling, I don't have a reasonably handy solution. I'm thinking of switching to an electric fuel pump. Worked wonders for my '66 Riley (classic mini varient). Might just be that the replacement mechanical pumps just aren't up to the job anymore?

Cheers and good luck
Daniel

 

[criceo]

The engine turns fine by hand with the pulley. The cylinders, head, valves, valve springs, and piston rings were replaced. I'm getting adequate fuel to the carb; so, I doubt the pump is the issue. Had an inconsistent idling problem with the previous carb; so, maybe the new one is at fault for this issue.

 

[the hobbler]

The engine turns fine by hand with the pulley. The cylinders, head, valves, valve springs, and piston rings were replaced. I'm getting adequate fuel to the carb; so, I doubt the pump is the issue. Had an inconsistent idling problem with the previous carb; so, maybe the new one is at fault for this issue.

Whilst I do realise that the original carb was not allowing for a consistant idle, have you tried re-fittting the old carb to see if the engine will start, albeit not running 100%

 

[dangfiat]

Has anybody found that an electric fuel pump helps these issues?

Perusing the forum it seems that rough idle and cutout on throttle are common issues. Just trying to figure out how to cure mine and find a lasting solution for the community. I know we're all DIY'ers and just trying our best to keep a loved little car on the road.

Love the helpful set of folks here! Seriously, between the Mini and Fiat crowd ya'll are tops

Any thoughts on why many of us experience this welcome. Let's get these little cars to be at least as reliable as their British counterparts!

Thanks all! I'll keep adding parts & trying new solutions. Any advice is super welcome

Cheers
Daniel

 

[Goldnrust]

The way I see it, 500s are such simple little cars that there’s very few things to go wrong, and yet that very same simplicity can sometimes make the problems seem less obvious.

For example, in the case of the problem @criceo has, if the engine really does have fuel, compression and a good spark at the right time, it will run.

But it’s quite easy to see a spark and go ‘that’s fine’ when really it’s a weak spark. Or to see a carburettor which looks clean in the float bowl but has a gummed up emulsion tube.

As I know well from my time with 2 stroke motorcycles, sometimes the simplest engines can throw up the most frustrating problems!!

What were the compression numbers you got @criceo? Were they even on both cylinders?

Condenser issues, including units that are failed from new are common. Valve clearances closing up seems to be another common cause of running issues. And air leaks from the base of the carb due to warped mating surfaces in the carb and carb spacer is another common one.

 

[Toshi 975]

If the carb is brand new then it is 99% sure to be at best one of the Spanish made Weber carbs which have been problematic in some cases or at worst a Chinese fake which are a bit of a no no.
Having said that I did manage to get my hands on a Spanish one which I totally stripped to see if I could find any faults and I could not and the guy it went to was very pleased with it.

 

[criceo]

Hey all. Still going through possible solutions. Compression is even on both cylinders. Carb box says it's made in Czechoslovakia; so, definitely not a brand new carb. Will see if the old one at least gives us some life. I'll keep you all updated! In the meantime, just scored an '88 RR Silver Spirit for about what I payed for this little red tempremental clown car. Funny how cars are priced sometimes!

 

[dangfiat]

Hey all. Still going through possible solutions. Compression is even on both cylinders. Carb box says it's made in Czechoslovakia; so, definitely not a brand new carb. Will see if the old one at least gives us some life. I'll keep you all updated! In the meantime, just scored an '88 RR Silver Spirit for about what I payed for this little red tempremental clown car. Funny how cars are priced sometimes!

Just had the same sort of problems (with a 650cc and an 28mm IMB).

Turned out, I had to do the following:
1. Check timing, change points/condenser. Get a timing light on it (even at cranking speeds) to check if you can
2. Check/set tappet clearences
3. Recheck/set timing
4. Pull the carb, pull all the jets/tubes/etc and blow through all of them with copious amounts of carb cleaner.. go nuts!
5. Put it all back together with new gaskets (and a new spacer)

Cured all my starting problems. Thing starts on choke fairly quickly

I think your problem sounds like a fuel issue, like there's something in the carb passageways/etc. Maybe a good clean will do it?

Also, get a spark plug extender and check your spark just to be on the safe side.

There's only fuel/air/spark to deal with. You'll get there!

 

[Toshi 975]

Made in Czechoslovakia is a new one on me

 

[FR85]

Hey all. Still going through possible solutions. Compression is even on both cylinders. Carb box says it's made in Czechoslovakia; so, definitely not a brand new carb. Will see if the old one at least gives us some life. I'll keep you all updated! In the meantime, just scored an '88 RR Silver Spirit for about what I payed for this little red tempremental clown car. Funny how cars are priced sometimes!

RR Silver Spirit......and you thought the 500 is giving you problems! My dad is a RR man, has two Silver Shadows. He swears by two things, get the rear suspension filled with grease and then block it off from the rest of the system and rust treat everywhere, Fiats fell apart thanks to the tin worm, RR were every bit as tasty to the tin worm.

 

[Goldnrust]

My Daimler (common as muck compared to a Rolls, but also a relatively luxury classic British motor) was also not much more to buy than my Fiat cost me, but restoring it and running it... thats a different matter. You can basically add a 0 to the cost of Fiat parts. Not to mention 14mpg... haha.

 

[FR85]

My Daimler (common as muck compared to a Rolls, but also a relatively luxury classic British motor) was also not much more to buy than my Fiat cost me, but restoring it and running it... thats a different matter. You can basically add a 0 to the cost of Fiat parts. Not to mention 14mpg... haha.

Jags, Daimlers, Rolls....when they're singing they are fabulous but when they aren't well....
The Citroen Hydrodynamic Suspension used by Rolls, top class when it's working but the plumbing is unreal.
Electric gremlins too can be tremendous fun and you are correct, move the decimal point a few places when it comes to some repair bills but with that said there is no point in being the richest man in the graveyard.

 

[criceo]

Hello all.

Still trying to revive this little clown car.

Will make sure to follow the basic checks suggested; it's always the easy and obvious that trip one up. You are sure you've covered all possible points, but there's something simple hiding in plain sight.

If anyone has experience with, or has even seen, a Czechoslovakian carb, let me know. May be worth putting it through a dip in one of those ultrasonic parts cleaners.

As for the comments about British beauties, this is far from my first rodeo. The parts may be pricey, but the level of craftsmanship that went into the cars originally mean that, with proper maintenance, failures are rarely catastrophic or without warning. But, no matter how comfortable and beautiful they are, absolutely no Rolls, Bentley, or Jag, examples of which I am the at times happy other times unhappy caretaker of, will ever turn half as many heads as a 500!

I'll keep everyone updated on how the situation progresses; I hope we're reaching the end of this particular saga.

 

[criceo]

Also, forgot to ask if anyone has experience with switching to electronic ignition. That was an upgrade installed during the rebuild. I'm not sure that it could be the culprit for a sudden death of an engine, but one never knows.

 

[Toshi 975]

Also, forgot to ask if anyone has experience with switching to electronic ignition. That was an upgrade installed during the rebuild. I'm not sure that it could be the culprit for a sudden death of an engine, but one never knows.

I have run just about all of the ignition options, standard and electronic, as I am sure others have on this forum. They are all generally successful but there may well be failures. Basically if you are showing a spark and the timing is right the engine should start. Your story is a little unusual in that you seem to have had all of the top end of the engine replaced apart from the pistons. Probably not relevant but why was that because you only mention uneven tick over?
As Peter said thrashing a newly built engine within the first hour may not have helped your cause. Short of stripping and rebuilding the engine I think you will need to focus on different aspects as a process of elimination. Pictures, data and observations can be most useful. I would be interested to see pictures of the carb you have (or even the box) as to my knowledge no 500 carbs were made outside of Italy until the more recent Weber made under licence ones appeared on the scene apart from a few rather nasty unbranded Chinese fakes.

 

[FR85]

Also, forgot to ask if anyone has experience with switching to electronic ignition. That was an upgrade installed during the rebuild. I'm not sure that it could be the culprit for a sudden death of an engine, but one never knows.

I had one of those simple electronic ignitions and funnily enough the car stopped dead one day, it would idle but very rough, went through the carb, timing, tappets ect and left it for a month, old school dad comes along and says take the point and condenser out of the spare engine and give it a lash, hey presto. Timed it again and that's now how I'm running. In my head it couldn't have been the ignition cause again in my head it was bullet proof. I had posts up about it. If it turns out not to be this it would be wise to carry a points set up as a spare for if and when the day does come.