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MG MGA - Warning Carb Float Failure

I mentioned this in another thread but I think it worth mentioning under the correct heading.

Last week I couldn't stop the front float chamber pumping petrol out of the overflow. After much fiddling with the valve I checked the difficult to extract float and it clearly had quite a bit of petrol in it. Changing the float for any empty one immediately solved the problem. I presume this was as a result of the alcohol in petrol attacking the solder joints.

My point here is that perhaps we should check our floats as a routine maintenance check as I suspect it had been filling over quite a period. After installing a spare from another carb I ordered a replacement from MGOC and it was still the same construction, are there alcohol resistant ones available anywhere?

Incidentally my final incident happened by a small housing estate in the country. Almost immediately after stopping a helpful guy came over and it turned out he was a Morgan aficionado, then a Minor drove by and pulled into the estate and the driver also came across. Seemingly these 2 neighbors had always been aware of each others cars but had never spoken so introducing them was a useful benefit from my problem, they carried on talking as I left.

As an aside this Thursday, problem fixed, I was driving over my favorite bit of 'test' road that goes over the hill by the Knockhill Racing Circuit. There was a red transit type van in front of me that I surprisingly wasn't caching except on the climbs. Anyhow when we got to the circuit entrance the van turned in and on the side it said 'Ducatti Glasgow' so perhaps his turn of speed wasn't that surprising if it a bike racer at the wheel.

Paul

Paul Dean

Burlen (SU) supply a range of 'Stay-Up' floats specifically designed for fuels containing alcohols............................Mike
m.j. moore

Mike

I had tried the Burlen site before going MGOC and thanks to you I have now found them. Logically I had taken the SU tab on the site and under that there doesn't appear to be any mention of alcohol resistance floats and they list brass one only. You have got to know to take the Stay Up tab from the top level. Stay Up appears to be a separate part of the Burlen group. As an ex professional in this area I would call this web design as pretty poor if I was in a good mood!

I will carry my spare in the meantime.

Paul
Paul Dean

Alcohol does not attack solder!
Art Pearse

These floats have been leaking long before ethanol was put in fuel! However, I agree that it is good practice to check them periodically.
Neil MG

Paul - If the car sat long enough for all the fuel to evaporate from the float bowl, it is not uncommon for the float lever to drop far enough down to allow the needle valve to trap it (the lever) and not allow the float to come up with the fuel level and therefore not shut off the flow of fuel from the pump. This can be cured by adjusting the tang on the back end of the float lever to limit the amount of drop. See the article Float Lever Drop Adjustment in the Other Tech Articles section of my Homepage at: http://homepages.donobi.net/sufuelpumps/ You can also find the same article in Barney's web site. Cheers - Dave
D W DuBois

Thanks for the comments. It is good it isn't alcohol so I should get the same 40+ years out of the replacement. Dave, thanks for the comment but not the issue here as my car has been in fairly constant use.

Thanks all round.

Paul
Paul Dean

Ethanol is a powerful solvent that attacks many fuel system components including zinc and galvanised materials, brass, copper, aluminium, seals and hoses, cork, polyurethane and epoxy resins. In other words, almost everything used in a vehicle made more than about 20 years ago. It’s also hydrophilic, and water causes all sorts of additional problems.
So our brass floats are attacked slightly by our 5% ethanol fuels. Mine are definitely very clean looking where they are in the fuel, I wouldn't be at all surprised if they sunk one day.
My sender unit and the inside of my carbs look too clean are they being attacked? - they are zinc alloy.
Pete
PeteT

I have a pet theory about alcohol in fuel.
Firstly I don't believe that ethyl alcohol (EA) itself is aggressive to metals in the fuel system.

But.... it is well known that EA in the presence of oxygen (air) is converted slowly to acetic acid and this acid is known to be aggressive. For example acetic acid does slowly dissolve lead (one of the few acids that does) which is, of course, the main constituent of the solder used for the float chambers.

Also, as anyone tasked with cleaning up brass and copper kettles will know, acetic acid does a very good job!

So I reckon it's the conversion of the alcohol into acid which is responsible for the damage not the alcohol directly.

This would mean that anyone who uses their car frequently so that the fuel/EA doesn't hang around anywhere in the system too long will not suffer any consequences but if, like many of us with a classic car, it is not used in the winter months this is when the 'damage' could occur. The SU float chamber fuel is partially open to the atmosphere so the oxygen could get in via this route as well as through the filler cap to the tank fuel.

I'm not entirely sure this idea would stand scrutiny by a professional chemist but I throw it out there for comment.................................Mike

m.j. moore

Interesting theory Mike. I run my car throughout the year, although during the winter months now it is just the once or twice a week to keep things turning over. I have the good old fashioned floats and have not as yet noticed any deterioration. I also run super unleaded. I have noticed a number of discussions on the web questioning whether there is ethanol in this fuel, or at least less than standard unleaded. Does anyone have the current status? Plenty on historical myths etc. My normal fill is Esso Super.

Steve
Steve Gyles

This thread was discussed between 19/04/2015 and 24/04/2015

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