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need fuel pump diaphragm material

Hi, all,

I have asked this before, and didn't get an answer that pointed me to a source. Well, the thing popped again, so I am in need again. I made a little fuel pump for my insane yard tractor rebuild some years ago. I used some misc. rubber material for the diaphragm, and it holds for about

2 years, then starts to leak. I bought some stuff specifically sold for this purpose, with some cord sandwiched between Neoprene. it is really too stiff for the little motor, and it only lasts a couple months before is breaks up at the cors and starts leaking. Grumble! So, does anyone know of a source for a good pump diaphragm material that can take continuous exposure to auto gasoline, and is still pretty flexible? I might have to buy some cheap mechanical pump and take the diaphragm out of it, or find a tiny commercial fuel pump that I can use.

I don't need a lot of head pressure, this needs to lift the gas no more than one foot, and deliver maybe 2 GPM if it was on all the time.

OK, here's the whole scoop (I ought to put pictures on my web site.) It is a 1968-vintage Bolens tractor with a 12 Hp Wisconsin engine. It had this hideous little updraft carb that was poorly made to start with, and in worse condition, with no parts available. I had a Honda motorcycle carb laying around, and jury-rigged it, and it worked great. But, it needed the gas delivered higher than for the updraft carb. So, I put a little header tank above the carb, and put a float switch in the header tank to turn on the pump when the tank was low. This all works fine, except for the pump diaphragm.

Thanks in advance if anyone can point me to a source of a good diaphragm material.

Jon

Reply to
Jon Elson
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Jon, you're making this far too difficult for yourself. Bypass the mechanical fuel pump and go buy a simple universal electronic fuel pump from an automobile parts store. Like these Purolator pumps from

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Purolator PRO04SV: Fuel Pump, Universal Electronic; Solid State; POSI-FLO® Pump; 1.5-4 PSI; 25 GPH;

3 Month Limited Warranty Ships in 1 day $39.99

Purolator PRO06SV: Fuel Pump, Universal Electronic; Solid State; POSI-FLO® Pump; 4-7 PSI; 32 GPH;

3 Month Limited Warranty Ships in 1 day $39.99

With one of these, you can probably scrap your makeshift header tank too.

Regards, Michael

Reply to
DeepDiver

Jon, You could go find a junker tractor someplace and take the vacuum operated fuel pump off the side of the engine. They have an "in", "out", and vacuum port which works of the stroke of the engine using the crankcase vacuum. You wouldn't need the extra tank above the carb and they last almost forever. Ken

Reply to
Ken Sterling

It's not cord-reinforced, but Santoprene sheeting will take the exposure to the solvents. It's a modified polypropylene/butadiene rubber; immune to most solvents. Not great on heat, though.

LLoyd

Reply to
Lloyd E. Sponenburgh

The vacuum fuel pump on my old 18HP Sears tractor was made to mount on the firewall instead of the carburetor so one like it would be even easier to adapt.

It didn't work when I was given the tractor (not much else did, either), but it just needed the rust from wet coast-of-Maine gasoline cleaned out.

jw

Reply to
jim.wilkins

OK, do you know where to get some of this? It sounds like something to try. I really don't know what the problem here is. As the existing material lasts 2 years, I don't think it really is a solvent breakdown problem, but a wear problem, or maybe a combination of the two.

Thanks again,

Jon

Reply to
Jon Elson

No, the motorcycle carb is designed for very low gravity fuel pressure, and I don't think it likes any more than a few inches of head above it. These things are $40 plus tax, and then I'd still have to add a check valve (I think) and a switching circuit to turn it on and off. It delivers way too much fuel, so I'd probably need an orifice to throttle it back some. It does look like it would work after all these adjustments were made, though. 25 gal/hr? Who could possibly need that much fuel flow?

Jon

Reply to
Jon Elson

Mcmaster.com sells all kinds of elastomer sheeting, some with fabric reinforcing. They have Viton which is quite fuel resistant.

Randy

Reply to
R. O'Brian

web site and see if I can find it.

Jon

Reply to
Jon Elson

John I think that jet-skis and similar watercraft use a fuel pump that has enough head for your application. IIRC, the exhaust gas pulses operate the pump, but I may be wrong. Sound like what you need, though.

Reply to
carl mciver

How about viton? Excellent resistance to oil and fuels and high temperatures. See

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part 86075K31. It's a little stiff at shore 75A but should work ok. Browse their catalog, you might find something better. I know they have buna N as soft as 50A but I think the viton would resist the fuel longer.

-- Regards, Carl Ijames carl.ijames at verizon.net

Reply to
Carl Ijames

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