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In a previous topic on fuel pumps/vapor lock there was a post saying that if a fuel pump was rebuilt over 5 years ago the diaphragm would be damaged by ethanol. Instead of refuting with my personal opinion and getting into a he said/she said 30 entry folly, I decided to do a controlled experiment to find out for myself what the truth is.

We used to sell FP rebuild kits up until 1993 when our supplier Kem Manufacturing stopped producing kit components.
We have a smallamount of components including diaphragms.
I took a new diaphragm likely over 20 years old and put it in a tray of 10% ethanol gas for a week adn had another diaphroagm as a control.

There was no softening, distortion, disintegration or other sign of and negative effect.

We have in stock about 25,000 old stock new and rebuilt pump adn have been selling form that stock for years. If a pump has an old style "tar" laminated diaphragm we replace them, if it is a new style rubber diaphragm we sell it after testing the valves. we have never gotten back a pump we sold where the diaphragms failed due to ethanol that we know of. Kem and Airtex used modern type material since the 40's, AC used laminated old style for many years after that.

In my opinion, supported by my experiment, it is not true that ethanol disintegrates diaphragms in pumps rebuilt more that 5 years ago. The biggest reason for fuel pump failure is rust in the gas tank clogging fuel pump valves and filters.

I'll confirm Fred Kanters claim. I have a mechanical pump on my 56 Executive that has been on there for at least 13 years or more that i know of. It has continuously had gasoline in it. It has worked flawlessly. I believe it is from Kanter Auto parts because the former owner bought exclusively from Kanter. He owned the car about 3 years or longer before i got it. It has not dried out nor deteriorated nor anything negative.

However, i'm not sure that a one week test of any parts in ethanol gas is long enuf. A recent needle and seat problem in another make ran about 1 year before any significant distortion occured to the 'rubber' tipped needle. IT swelled and caused the float to drop about 50%.

On the other hand, my 56 Executive has "rubber" tipped needle for over 13 years and it shows no signs of distortion or any other problem.

88 ranger fuel pump replaced about 5 to 8 years ago (i'd have to double check my record book for accuracy), NO problems with it.

The biggest problem i've ran into is the 'rubber' tipped needles. Some distort. SOme don't. How does one test a needle to determine if it will distort or not??? Soaking is the only way that i know of.

In a related question, I have a rebuilt carb for a 1954 Chrysler six that I bought at an auction a couple of weeks ago. It was still in the box as supplied by the rebuilder.

Judging by the newspaper that was wrapped around the carb, it was rebuilt in 1965.

My question is, if the carb is safe to use as is or if I should buy a kit and rebuild it again? This is a Carter B&B carb with the electrical switches for the fluid drive trans.

I would put it on and try it. Just be aware that if it has a 'rubber' tipped needle then it is possible that it mite swell. Rebuilt or new in 1965 there is strong possibility it has a solid metal needle. Only way to know for sure is to either take it a part or just go ahead and try to run it and watch for signs of lean condition.

An overly lean condition will usualy occur on a long hill or high speed, loosing power. There will almost always be a 'pup' pup pup sound to the exhaust when loss of power occurs. DO NOT force the issue when that happens. Limp it on home slow enuf speed to correct it.

As usual, Fred is correct. The OEM fuel pump in one of my '55s has functioned on 10% ethanol for fifteen or twenty years.

jack vines

The biggest problem of fuel incompatibility with diaphragms, needle seats or gaskets is the type of rubber that was used, not necessarily the age of the material.

Some typical rubber materials with a chemical compatibility chart.

allorings.com/compatibility.htm

Note the big difference between materials that may look identical.

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