FuelPump Mythbuster #1

Posted by fred kanter On 2011/6/2 15:24:51

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.