Technical Newbie question

[t8rco]

Hi first post so go easy on me,


Got a 1970 500L starts fine when cold and drives fine when cold but after a while once warmed up it seems what feels like dropping a cylinder and power big time and pretty much cutting out at low revs.



When you let it cool down it then starts again as normal on two cylinders.
Also this morning saw oil on the floor to under the center left of engine not loads but size of an iphone.


Any advice welcome.


Cheers


Mark

 

[the hobbler]

You say "starts fine cold and runs fine cold"---is this whilst the 'choke'is still on? If your poor running starts when you stop using the 'choke', there is a good chance that you have a blocked 'slow-running' (idle) jet. Try removing the carb, remove the jets (noting carefully where things go) and give the carb and the jets a good clean and blow-through. Whilst the carb is off, check that the bakelite space is not warped. put it all back together, see how it goes and report back to us. Let's try to sort one problem at a time. Where are you based---it might be possible to put an experienced owner/forum member in contact with you.

 

[t8rco]

Hi thanks for the reply, I don’t really use the choke other than 1 or 2 minutes. It drives well without choke when cold it’s when it gets hot the problem arises. I’m based near Guildford UK

 

[BambinoClassic]

Have you checked the valve clearances?
Relatively easy and often successful place to start for this problem I think
Good luck!

 

[the hobbler]

In the light of your answer, the suggestion of checking tappet clearances is a good one---the 500s do have a tendency for the tappets to close up. If they are too tight, metal expansion could mean that they are not fully closing when hot.

 

[t8rco]

Cool thanks guys I’ll check tappet clearances first and report back. The book says it should be 0.006 inch or 0.15mm right?

 

[the hobbler]

That is correct--with the engine COLD. The simple proceedure is to work "the opposites" trick---when the tappet for the exhaust on cylinder 1 is fully down, the exhaust tappet for cylinder 2 should be 'on the rock'---now adjust it. When the tappet for number 1 inlet is fully down, the inlet for no 2 should be 'on the rock'--adjust it----and the vice versa for the other tappets. They should be adjusted so that you get light resistance when you pull the feeler gauge through the gap.

 

[t8rco]

Hi Guys,

Long time since my last post but have been in hibernation!! So I have done the adjustments as per the instructions however its still has the same problem. After 10 mins of driving when the car has warmed up its seems like its dropping a cylinder and power big time. However when its cold its fine


Anything else to check?

Cheers

Marco

 

[lazylobster]

I had this. My car was fine cold, then when hot, misfire, dropping a cylinder. Turned out to be a dodgy spark plug.

Get a multimeter on the plugs and the leads. If you see some resistance, there is your answer.

As a matter of course, I swapped out the rota, dist cap, leads, plugs and coil. It's not a huge expense and future proofs (as much as you can!) the enjoyment and reliability of the car.

R

 

[t8rco]

Thanks for the reply, what did you replace the system with? Did you go electronic ignition?

 

[lazylobster]

Hi, yes I went powerspark. So far, so good.

As others will mention, condensor and points are weak point of the platform.

Silicone leads, viper dry resin coil (no oil). My car starts easy when hot / cold or inbetween.



Cheers
Rob

 

[t8rco]

So looking into the replacing the ignition system and found this one but not sure if there is a better version, any thoughts out there?

https://www.ricambio.co.uk/69-fiat/...ctronic-distributor-kit--classic-fiat-500-126

 

[the hobbler]

The "123" system is good, but expensive. A better idea, as you are not quite sure what the problem is, to fit one of the "Hall" effect systems. These are 'simple' electronic ignition kits and come out at between £40-£70, depending on which kit you buy. The main systems seem to be:--AccuSpark, Powerspark and H&H.
Have you checked the coil (getting very hot?) and/or made sure that the choke is coming completely off?
As you live near Guildford, it might help you if you can find a 500 owner in the area who can help you.

 

[fiat500]

Toshi 975 put me right with the correct way to check valve clearances; the "1 off 5" method. Carefully turning the engine clockwise manually with rocker cover off, look for the first arm that pushes the spring on a valve as far as it can. Note the number of that valve from 1 to 4 with 1 being the one closest to the back of the car.
Subtract that number from 5 and it is the valve with the resulting number that should be adjusted.
Keep going until all valves are adjusted and ideally do a double-check. Other methods may not be accurate.
Electronic ignition is good but unless your distributor is very worn it won't necessarily solve any problems.

 

[Paolo66]

Valve clearances
https://www.fiatforum.com/showthread.php?t=341467

This explains it well enough

 

[hamiltos2]

Worth checking for distortion on the carb flange.

I had exactly the same symptoms , tried everything whilst I was quietly going bonkers with the problem.

Last resort I checked trueness on the flange and guess what , it measured up rather like a banana....

Apparently the hotter the engine gets, the more it distorts / leaks.

 

[t8rco]

So it turns out to be the condensor on the side of the distributor just so you all know, watch out for that one.

 

[lazylobster]

Thanks for the reply, what did you replace the system with? Did you go electronic ignition?

Condensor = weak point. Whack in an electronic ignition and job done

 

[gordinir8]

I will highly recommend the powerspark ignition as Tom mention before. It will save you a lot if trouble and make your engine run remarkable smoother, and all this with 50 euros. Ofcourse I keep the old points system in the car in a case of something go wrong.

 

[the hobbler]

Interesting that the problem turned out to be the condenser, but not surprised. The 500 has a healthy appetite for condensers! The majority of the modern-made condensers are cheap rubbish. If one does want to retain the original points system, fit a really good condenser. I have mentioned this company before---"SWIFTUNE" Their competition condenser (SW-1G-CC) is designed for the classic racing cars where the regulations compel the use of the 'as original' ignition type, be it a mini or a Ford GT40! Whilst I still had points ignition on my engine I fitted one of these condensers---never had a moments trouble. Admittedly, these condensers are not cheap (about £36 inc carriage), but you are very unlikely to suffer condenser trouble again.