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Classic Engines, Modern Fuel

Comments on Topic: Plastic floats - are they affected over time or not?.

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Submitted by Rich
14-Jun-2021

Hello Paul,

I have tried to do my own research on this, with mixed results sadly.

Do we have any conclusive evidence to suggest that plastic floats are eventually affected over time by adding Ethanol to fuels, some sites say not whilst others do?.

I have a set of twin webers which use what i gather to be called Nitropyhl black plastic floats, some say these are ok with E5/10 whilst carbs using Nylon floats ( white) are not suitable, can you please perhaps give any advise for owners of such carbs, I think I am correct in saying that brass floats using solder to seal them will be affected badly, is this correct as well please.

Well done on the book by the way and the help it continues to do

Thankyou

Rich

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Submitted by The Author
14-Jun-2021

Rich,

Thanks for the positive comments on the book.

Unfortunately, I have not done any testing myself on plastic floats. As you are probably aware there are many different types of plastic so it could depend on which one they are made from.

As you can see from the photos in the book, my original tests were done using polythene "pots". These were not affected. However, I used, what appeared to be, the same type of polythene boxes for the second set of tests. These were affected by the petrol becoming distorted.

There is a reasonable explanation of the affect of alcohol on plastics here but I do not think it really helps unless you know what plastic your floats are made from. My "gut feeling" is that petrol is probably more damaging to plastic than ethanol. So if your floats have survived, they will be OK with ethanol.

As I suggest in my book. It is worth keeping a careful "eye" on your fuel system to watch for leaks. If you have an electric fuel pump, leaking floats are relative easy to spot. Your pump will not stop "clicking".

As for brass floats and solder. Yes, brass floats are soldered together and yes, lead based solder can degrade over time. However, this is caused by the petrol, not the ethanol. Since the demise of leaded petrol, modern petrol tends to dissolve solder. This is a very slow process and again very easy to spot - overflowing float chambers.

The brass floats in my car are about 20 years old and are still OK.

Kind regards

Paul

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Submitted by Rich
14-Jun-2021

Thank You Paul, a very fast response.

I am fairly sure of the material my floats are made from so I will have to carry out further research into this, but as you say they are currently still operating correctly and I have no clue how old the carbs actually are, I have had the car 14 years so they are at least that, and that is with using E5 all that time. I would only replace them for the same items as a 'piece of mind' change.

Nice to know you think Ethanol isn't doing the damage the solder on brass floats as I seem to read on the web all the time, I do know of at least one car that had an engine fire because of failed floats, which was blamed on Ethanol looks like this conclusion was incorrect.

Also, with the greatest of respect, may I contradict your comment on electric fuel pumps ...

Not all electric fuel pumps will stop clicking when the fuel valve is shut in the float chamber, many do yes but not all. I run and have run for many years now a pump from the USA made by Facet, the newest range of which continue to click even when the valve is closed they are designed to do this to maintain pressure in the lines. I apologise for being pedantic but facts like this matter to me.

If you permit me to add this from a supplier of such pump taken from a FAQ page.

Q - My new Facet pump seems to run constantly, but the old pump used to slow down or stop. Is the new pump defective?

A - No. All current Facet low-pressure pumps run constantly as long as power is supplied.

Older Gold-Flo (cylindrical) pumps were known as "Interruptor" pumps because they would start off pumping very quickly, then slow down as they built pressure. They might even stop completely once they reached their design pressure. The interruptor behavior went away when Facet changed the Gold-Flo series from breaker points to the same solid-state operation as the cube-style pumps (around the late 1990s). The part numbers for solid-state Gold-Flo pumps have an E at the end to indicate "Electronic" operation. During the transition, Gold-Flo pumps with breaker points had part numbers that ended in I (for Interruptor).

Note that we still use the original part numbers without a letter at the end, even though all Gold-Flo pumps are now the E (Electronic) version.

Some more work needed on Nitropyhl flaots and if I get anywhere I will post back on the subject.

Many Thanks

Rich

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Submitted by The Author
15-Jun-2021

Rich,

You make an excellent comment about an electric pump not always stopping when it reaches the correct pressure. I was not aware of the Facet pump running on, but it also true of cars with fuel injection such as the Triumph TR6. In these cars the pumps run continuously.

The point I was trying to make is that these are old vehicles and their fuel systems can degrade. Even before ethanol, petrol hoses can perish, fuel tanks can rot and needle valves in the float chambers can wear. Any degradation can lead to fuel leaks.

This is something a classic vehicle owner must me aware of. Any indicators such as a petrol pump that should stop, continuing to click can help to spot leaks. But there are other causes that a clicking petrol pump may not show.

A WARNING. Petrol vapor is highly flammable, a spark from a light switch, static on a shirt, etc. can be sufficient to ignite it. This is even worse with modern petrol because more of it will evaporate at lower temperatures.

Should you smell petrol in your garage, carefully open all the doors and do not do anything until the petrol vapor has dispersed.

Kind regards

Paul

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Submitted by Rich
15-Jun-2021

Thank You Paul,

Well I have spent the best part of the morning attempting to get some solid data for the effects of Ethyl Alcohol on plastics, with once again mixed and confusing results, I have to state at this point I have no chemical qualifications what so ever , so I try and find sites that do, or at least the authors of such sites. I never really take my data from a typical forum style sites either as they often have the wildly differing opinions often based on 'pub talk' which serves no one any good.

I have found two reasonable sites so far with data clearly presented, although even these differ in their results.

I include both links for folks to look at.

https://www.terrauniversal.com/blog/chemical-compatibility-chart-plastics/

and

https://www.theplasticshop.co.uk/plastic_technical_data_sheets/engineering_plastics_chemical_resistance_guide.pdf

The PDF one takes a bit of working out, but from that one Ethyl appears to be resistant for all tested plastics except one called PSU 1000 which is a polysulphone resin which it states is partially resistant.

more info here on PSU 1000

https://www.theplasticshop.co.uk/psu-1000-polysulphone-rod-sheet.html

I am beginning to think that all the hype about the dangers of Ethyl are not as bad as a lot of the internet would suggest as far as it's use in fuels, you could argue about it's affect on the enviroment however as i did come across many papers highlighting the carbon it releases once burnt - however this is not the place to discuss that I don't think.

I am going to stick with the floats I currently use and keep a eye on them perhaps a bit more than I would do normally.

I am not sure if I have said this before ( I can't see the rest of the thread whilst typing this but) from what I have read both in books and the web, as long as you use the car fairly often, for me that is about once a week, I don't expect to have issues with any degradation over what would be the normal life span of mechanical car parts. A car left sat for months on end may indeed suffer with phase separation within the fuel, which would need to be addressed.

Anyway, that's my 2 pence worth for now.

Rich

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