Technical new owner 1971 500L Acceleration Problems

[srenton]

Hello All..
Im new to this having just bought a 1971 500L and could do with some help...
although difficult to start ( seems like the choke isn't doing a lot ) My car idles fine however when I drive and accelerate it splutters and stutters and generally isn't smooth at all. I know there could be many reasons but some pointers would be great.
Im imagining carb / jets need cleaning or fuel pump / line ( she's had new filters leads etc etc)
thanks in advance

 

[the hobbler]

First question---where about in the UK are you? If we know that, it might be possible to put you in contact with an experienced 500 owner.
All I can suggest initially are the basics. Remove the carb and get it ultrasonically cleaned, and whilst the carb is off, check that both surfaces of the bakalite spacer is flat as well as the base of the carb. Check the tappet clearances (cold)--the 500 is infamous for them closing up. If you still have points ignition, fit a high quality condenser (from Swiftune). You do not have a 'choke' on the 500 carb--it is a "fuel enrichment device"---there is no 2nd butterfly. Check that fuel lines are clear and that all the filters in the system are clear, especially if the car has been standing for some time with modern fuel in it. There is NO need to fit additional fuel filters--the standard system has 3 from factory (tank unit, top of fuel-pump and carb). Check the timing--if you still have points ignition this can be done 'statically' with a test lamp--10deg (13mm) btdc.
This is difficult question to give a precise answer to, but the above should help you eliminate basic faults.

 

[Alfadeke21]

One thing I did was to ensure that both the slow running and main jets were clear by taking them out and blowing them through. The first time I did this it made no difference so I took the carb off and then took off the top cover to get at the main jet. Then I removed the emulsion tube (the bell mouthed bit beside the main jet holder) visible in the main body and checked the holes at the bottom of the tube where I found the remains of a tiny neoprene seal was blocking the lower orifices. Clearing that and checking all four holes were clear, reassembling & refitting the carb, it started and ran well with no hesitancy and smooth acceleration right through the Rev range.
This might help to fix things?
Derek

 

[srenton]

many thanks for this.
im in North London and im told the car had a 650cc FIAT 126 engine,
any help would be appreciated if someone lives local
thanks

 

[srenton]

thanks Derek
Is this something that a novice could do?
I've worked one cars doing bits and pieces back in the day but am by no means a mechanic.
do you know of a step by step guide? the Haynes manual isn't great for this sort of thing.

 

[the hobbler]

The carbs on the 500 and the 126 are almost identical---if you would like to contact me direct with your address--- [email protected] I will copy the relevant pages out of the factory workshop manual and post them to you.

 

[Toshi 975]

many thanks for this.
im in North London and im told the car had a 650cc FIAT 126 engine,
any help would be appreciated if someone lives local
thanks

I am located in Chesham , north west of London & just outside the M25. I have rebuilt many 500 & 126 carbs for myself & collegues over the years and have a small stock of gaskets, seals etc. If you were able to bring or post your carb to me I could rebuild it for you. I also still have one spare brand new Weber 28 for the 126 if required.
I need something to do now that I have been told I am not allowed out for 4 months.

 

[fiat500]

I need something to do now that I have been told I am not allowed out for 4 months.

Look after yourself Dave. Nothing implied against anyone in particular, but as someone with vulnerabilities, it's probably wise not even to exchange parcels etc. at the moment. ...especially someone with the surname Renton....remember "Sick Boy" out of "Trainspotting".

(Sorry srenton..just being silly )

 

[Alfadeke21]

I am located in Chesham , north west of London & just outside the M25. I have rebuilt many 500 & 126 carbs for myself & collegues over the years and have a small stock of gaskets, seals etc. If you were able to bring or post your carb to me I could rebuild it for you. I also still have one spare brand new Weber 28 for the 126 if required.


Toshi,
Included in the Weber gasket set is a tiny round neoprene O ring. I can’t find out where it really goes but since I found one at the bottom of the emulsion tube I assume it’s at on the top bell end?
Or does it belong somewhere completely different?

Srenton,
Do please remember that almost all fuel problems are electrical in origin!
Start first checking plugs, leads (ht & lt), condenser, points etc and eliminate each one at a time. Check the points gap and if you have to adjust that re-check the static timing as if that is out it won’t help starting! Refer to the manual for dynamic timing position 13mm btdc on pulley. Then start on the carb...

 

[Toshi 975]

Included in the Weber gasket set is a tiny round neoprene O ring. I can’t find out where it really goes but since I found one at the bottom of the emulsion tube I assume it’s at on the top bell end?
Or does it belong somewhere completely different?

There are no internal O rings on these carbs. On carbs with the recessed idle mixture screw there should be an O ring seal on the screw as there is also on the idle mixture jet holder. These seals tend to flatten and petrify with age so are often hard to see and also loose their effectiveness. Your stray seal is a mystery.

 

[Alfadeke21]

Aaah! Mystery solved - with thanks. Like you I'm "supposed to be incommunicado" for a similar time, although the Scottish "advices" are a little more relaxed at the moment.
Still I'm desperately hoping to make the Fiat 500 Dutch Club's "Festival Quarant'anni" celebration at the end of May......!