Technical Carburettor cleaning, what next.

[SDHXIII]

Hello.

You might remember me as the one that had no idea about engines and who couldn't really understand the language of the Haynes Manuals.
I have a problem with my 500 cutting out and then having troubles restarting.

Well I have managed to check and adjust the points and timing. That made a huge difference, the car starts first time and runs smoother and is that much more responsive.

But the car still cuts out.

My next point of call is the carburettor. I have taken the cover off and found that the chamber of fuel where the float lives does have a fair bit of gunge in the bottom. I'm presuming that this should should not be the case and if there is gunge there then there's likely to be gunge elsewhere.

So my question are:

1 - Having taken the cover off, how do I get the rest of the carb off. I can see two obvious bolts but understand that there should be four. Where are the other two please.

2 - What are the key areas I need to check for when cleaning, do I need to pay more attention to certain parts of the carb.

3 - The car had no fuel filter in place when I got it. I will fit one, but where is best? I have seen them before the fuel pump and I have seen them after.

3 - Given the carb has some gunge in, is it likely the pump will too and does this need to be dismantled and cleaned as well.

Answers or other suggestions gratefully received. Please can answers be in very basic terms given my level of ability ?

Many thanks, as always,
Stuart

* * * * * * * * * *

1969 RHD FIAT 500 (650cc) F

Made in Turin, 1969 ??
Came to the UK, 1992 ??
Full restoration, 2015 ?

? Instagram: FIAT_500f

 

[SDHXIII]

Gunge tank photograph. ?

 

[hodgy18]

Hi there- does it cut out when hot only?

 

[SDHXIII]

Cuts out after about half hour of driving, starts chugging and then cuts out. Usually at a junction!
?
It sometimes starts again straight away with accelerator full down, else I have to wait 10 minutes to start it again.

 

[g8rpi]

Hello.

You might remember me as the one that had no idea about engines and who couldn't really understand the language of the Haynes Manuals.
I have a problem with my 500 cutting out and then having troubles restarting.

Well I have managed to check and adjust the points and timing. That made a huge difference, the car starts first time and runs smoother and is that much more responsive.

But the car still cuts out.

My next point of call is the carburettor. I have taken the cover off and found that the chamber of fuel where the float lives does have a fair bit of gunge in the bottom. I'm presuming that this should should not be the case and if there is gunge there then there's likely to be gunge elsewhere.

So my question are:

1 - Having taken the cover off, how do I get the rest of the carb off. I can see two obvious bolts but understand that there should be four. Where are the other two please.

2 - What are the key areas I need to check for when cleaning, do I need to pay more attention to certain parts of the carb.

3 - The car had no fuel filter in place when I got it. I will fit one, but where is best? I have seen them before the fuel pump and I have seen them after.

3 - Given the carb has some gunge in, is it likely the pump will too and does this need to be dismantled and cleaned as well.

Answers or other suggestions gratefully received. Please can answers be in very basic terms given my level of ability ?

Many thanks, as always,
Stuart

* * * * * * * * * *

1969 RHD FIAT 500 (650cc) F

Made in Turin, 1969 ??
Came to the UK, 1992 ??
Full restoration, 2015 ?

? Instagram: @FIAT_500f

Hi,
There's clearly a lot of debris in the float chamber and it's likely it's got elsewhere. Please don't take this personally but if you are having trouble getting the carburetter off the intake manifold I'm not sure you are ready to tackle the carburetter on your own.
Where in West Sussex are you located? Maybe a member can help out. I'm north of Cambridge so a bit far away.
As a minimum you should clean out the visible dirt and fit an inline filter between pump and carburetter. The dirt may be from the pumpfailing, dirty fuel or a rusty tank.

Robert G8RPI

 

[Paolo66]

Apart from the dirt that has collected in the fuel bowl, the fuel itself looks clean as does the carb. What you could try doing whilst you have the fuel hose disconnected from the carb is, with an assistant, turn the car over and have the fuel hose in a clean container. If this then fills up with dirt you know its coming from the pump or tank and these will need addressing. Putting a filter on will stop the dirt getting to the carb but the filter will quickly get blocked and pressure will build up.
To get the carb off you need to disconnect the choke cable, the throttle rod and then undo those 2 nuts (awkward to get at one of them). There are only two nuts not four. You should replace the carb gaskets with new ones if you remove it.
Oh and I think its cutting out because your tappets need adjusting

 

[Fayray]

I found it easier to get to one of the two nuts holding the carb on if the tappets cover is removed. And as the tappets need adjusting, as Paolo66 suggests, you may as well remove it and deal to both issues at the same time.
I had no idea what I was doing when I did this a few months back but it wasn't too demanding. There is some excellent advice in the archives here that will help.
If you were able to adjust the points and timing then you won't have a problem with the carb and tappet adjustment. Tip - when replacing the tappet cover, don't over-tighten it like I did. The metal of the cover is soft so you will find it happily keeps tightening without too much effort but the area around the nuts will gradually bend down and it doesn't take much before it fouls the tappets and the engine won't run. It took me AGES to figure out what I'd done wrong:bang:

 

[SDHXIII]

The car had a reconditioned 126 650cc engine in January 2015 and a brand new fuel tank and associated parts in June 2015. One presumes that internal rusting of the fuel tank would not be a problem yet.

I have consulted my 126 & 500 Haynes and my 'AA Book Of The Car' and recon I will be able to have a go at the tappets. Any words of wisdom before I start?

Also is the 'main jet' in the carb adjustable or simple just screwed in? In other words can I remove it, inspect if for dirt and then put it back, or does it need a bit of fine tuning when replacing?

Can the main jet be cleaned in situ or must it be removed first?

 

[Paolo66]

For the tappets I followed this thread. Easy to follow

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

The main jet comes out and can be cleaned as can all the jets

 

[F123C]

The main jet will be found in the bottom of the float chamber.

None of the jets are adjustable, they rely on very precisely sized holes to meter the quantity or fuel or air that can pass. The only adjustments on this carb are the float level (usually not touched unless your replace a float valve or have a significant problem, which I don't think you have!) and 2 adjuster screws on the outside, one for idle mixture, and one for idle speed.

You need to remove all jets and blow through the jets and all drillings/passageways in the carb. body.

Be careful if blowing through jets with an air line/blowgun - it's really easy to lose your grip on a jet and send it somewhere you'll spend hours looking for it... (you could blow through the jets inside a container - plastic bag, box or similar to prevent them 'disappearing')

Don't forget to clean the carb. top cover. There's iirc a filter screen under a brass plug near where the fuel pipe is attached. Be careful with the float, it's delicate/easily damaged.

One very minor point, you could, when you have everything back together, align the operating rod on the carb. linkage so that the plastic ball-joints are nicely aligned/centralised with the ball studs they fit over, then nip up the locknuts. (then check the linkage over it's full range of operation to ensure that there's no binding).

I have to say the area around your carb. and other parts visible in your picture look in very good order - well done to whoever is responsible.

AL.

 

[SDHXIII]

Well, this morning I sorted the tappets out, seemed fairly straight forward. None of the tappets had any gaps, so adjusted them to Haynes 126 specification.

Went for a drive this afternoon, which was horrendous. The car cut out four or five times, sometimes it would fire up straight away and twice i had to sit and wait for 10 minutes. On a couple of occasions it died but fired itself back up as I was cruising to a halt.

This is very fast taking the enjoyment out of this car...

My next port of call is to find an expert and pay them for sorting this car out. If any one knows an expert or equivalent near to West Sussex, please, please let me know...

Thank you.

 

[Luxe]

Just a bit of a reach, but could there be a hole in the float? It seems to me that if there is a hole in the float on the bottom this would fill the float up after a bit and cause it to choke out the carb. While waiting to start, the bowl drains and the float drains allowing it to restart. Just a thought. Anyone second that?

 

[Vitesse]

Well, this morning I sorted the tappets out, seemed fairly straight forward. None of the tappets had any gaps, so adjusted them to Haynes 126 specification.

Went for a drive this afternoon, which was horrendous. The car cut out four or five times, sometimes it would fire up straight away and twice i had to sit and wait for 10 minutes. On a couple of occasions it died but fired itself back up as I was cruising to a halt.

This is very fast taking the enjoyment out of this car...

My next port of call is to find an expert and pay them for sorting this car out. If any one knows an expert or equivalent near to West Sussex, please, please let me know...

Thank you.

Depends how west you are in West Sussex? But there is a Company in Ringwood, Hampshire called Autorossa. It used to be a guy called Cliff but that was a few years ago. I don’t know if he still runs it but it still exists. He has been working on 500’s for years. http://autorossa.com

Tony

 

[IanEmery]

Went for a drive this afternoon, which was horrendous. The car cut out four or five times, sometimes it would fire up straight away and twice i had to sit and wait for 10 minutes. On a couple of occasions it died but fired itself back up as I was cruising to a halt.


Thank you.

Stuart, maybe a daft suggestion but are you sure that the enrichment device is fully returning? Your story just sounds to me like the engine is running too rich. :chin: :chin:

 

[SDHXIII]

Stuart, maybe a daft suggestion but are you sure that the enrichment device is fully returning? Your story just sounds to me like the engine is running too rich. :chin: :chin:

When you say too rich, do you mean getting too much fuel?
I checked the spark plugs which were sooty, Haynes says something about soot and richness I think.

 

[IanEmery]

When you say too rich, do you mean getting too much fuel?
I checked the spark plugs which were sooty, Haynes says something about soot and richness I think.

Stuart, looking at the photo you posted it looks as though the enrichment device, aka “Choke”, isn’t returning to its off position? This could be because the cable maybe needs to be re-routed so that the bends aren’t as sharp or that the inner cable is running tight in its outer? I’ve marked up on your photo.

Yes running rich means that too much petrol is getting into the engine and, if all the carb jets are cleaned and the float is properly set, there aren’t many other ways that the petrol/air ratio can be wrong than the enrichment device staying “on”

 

[SDHXIII]

Just a bit of a reach, but could there be a hole in the float? It seems to me that if there is a hole in the float on the bottom this would fill the float up after a bit and cause it to choke out the carb. While waiting to start, the bowl drains and the float drains allowing it to restart. Just a thought. Anyone second that?

When I took the the carb top off I looked at the float, could see no visible holes, but there was the very slightest of dinks on one end.

 

[Luxe]

I only mentioned the float because I had a similar problem. I removed the float and shook it and could hear some liquid in it. It had the smallest of pin holes that would allow me to drive for a bit and then it would sink and start flooding fuel into the engine. Essentially running too rich to the point of choking the engine.

 

[SDHXIII]

Stuart, looking at the photo you posted it looks as though the enrichment device, aka “Choke”, isn’t returning to its off position? This could be because the cable maybe needs to be re-routed so that the bends aren’t as sharp or that the inner cable is running tight in its outer? I’ve marked up on your photo.

Ian, thank you for all of your suggestions and advice so far, very helpful and much appreciated.

In terms of the choke, as far as I am aware there is no fouling in the system as is. On starting I pull the left leaver which moves something (enrichment device maybe!!) to the left of the carb (looking from the back) and once the engine is warmed up the choke is pushed gradually downwards in the cabin which in turn moves back the 'something' on the carb.

Could it be possible then, that before I even turn a key and lift the choke leaver that the 'something' on the carb is in the wrong position, that is, it is the position that it should be when the choke handle is lifted. And by then lifting the choke lever I am effectively applying 'double choke'.

All the signs are of two much fuel going in, the smell of petrol is quite strong at times, along with sooty plugs and (though never really measured) not marvellous fuel consumption.

https://www.instagram.com/p/Bdvedpznr7s/?taken-by=fiat_500f should take you to a video of the car starting, it does seem to show the 'something' on the carb moving before the car is started.

If it is possible that I am running double choke at times, is it an easy adjustment, or is it a new something from the car parts man in Holland?

As always, all help gratefully received.

 

[IanEmery]

Ian, thank you for all of your suggestions and advice so far, very helpful and much appreciated.

In terms of the choke, as far as I am aware there is no fouling in the system as is. On starting I pull the left leaver which moves something (enrichment device maybe!!) to the left of the carb (looking from the back) and once the engine is warmed up the choke is pushed gradually downwards in the cabin which in turn moves back the 'something' on the carb.

Could it be possible then, that before I even turn a key and lift the choke leaver that the 'something' on the carb is in the wrong position, that is, it is the position that it should be when the choke handle is lifted. And by then lifting the choke lever I am effectively applying 'double choke'.

All the signs are of two much fuel going in, the smell of petrol is quite strong at times, along with sooty plugs and (though never really measured) not marvellous fuel consumption.

https://www.instagram.com/p/Bdvedpznr7s/?taken-by=fiat_500f should take you to a video of the car starting, it does seem to show the 'something' on the carb moving before the car is started.

If it is possible that I am running double choke at times, is it an easy adjustment, or is it a new something from the car parts man in Holland?

As always, all help gratefully received.

Well the good new is there is no cost to check this! If you go to the carb first to make sure of full movement, undo the cable holding clamp bolt and check for full action by manually moving the enrichment control. While the cable clamp bolt is ondone I would suggest you get someone to operate the lever inside the car while you check the movement of the cable at the carb end. Your engine runs beautifully in the video after a few seconds but as the movie is quite short I can’t see if the enrichment lever is returning fully.

To answer your question: no, it’s not possible to effect “double choke” but it is quite possible for the carb enrichment to not be fully returned by the lever inside the car. The carb lever should move through approx 90 degrees.