Jon Elson wrote in message ...
Hello, all,

I made my own fuel pump for my lawn tractor. (Long story,
1968 Wisconsin one-cyl engine, carb vibrated to bits,
poor fuel feed when on hills, etc. So, I put a Kei Hin
carb off a Honda 450 motorcycle engine on it, and it runs
great, but needs a head of fuel above carb.) So, I made
a little pump out of a floppy drive motor, eccentric,
rubber diaphragm, and valves made out of ball bearings,
springs and standard flare fittings.

This all works great, but the diaphragms keep wearing out.
I started with some .060" Neoprene sheet that works well,
but lasts only 3 years or so. When it fails, it starts
spraying gasoline all over the place, which is NOT a good
idea! I bought some material specifically sold as "a diphragm
material for fuel pumps, etc." from MSC. It has nylon or
similar webbing in it. It is too stiff, but mostly works,
but it only lasts about ONE YEAR! What happens is the
"rubber" ,material swells up and disintegrates after long
exposure to fuel. The fuel pump diphragm in my 1989 Toyota
is the original factory piece, and is still working, after a
LOT more time and 137,000 miles. Does anyone know where to
get this kind of material, used in auto fuel pumps? I need
something that is pretty soft, as the motor doesn't have much
power, and that will last a long time, as I'm tired of rebuilding
this thing. Also, letting it run until failure is going to
involve me in a big fireball on of these days, and I want to
avoid that!

Hmm, maybe I already know the answer, JC Whitney?

Thanks in advance for all suggestions!

Jon


IIRC, the stuff they used to use was nitrile rubber with cloth
reinforcing. I don't know what's used these days, whatever it is, if
you're using pump gas, it's going to have to withstand MTBE, methanol,
ethanol and whatever other mouse milks they're running in the gas
these days. As you've discovered, neoprene really isn't suited for
today's gas. Might be you could get a fuel pump rebuild kit from(wait
for it) JC Whitney for some older model car or truck and use that
diaphram material. A junk yard would be another source, dismantle a
pump off a wreck and use the diaphram from it. Going to have be a
fairly old vehicle, fuel injection has been around a long time. I
hope you have some provision for emergency pump shutoff.

Stan