Gravity feed to replace pump?

[Beeman]

This isn't for a 6x6 (actually a little 1970's John Deere Lawn Tractor that I bought recently), but definitly engine related, so...

The fuel pump is shot on the engine, and I've heard that since the gas tank is higher than the carb the pump can just be bypassed. I always thought the pump, since linked to the crankshaft, was pumped every rotation to deliver the fuel to the carb (and so the faster the engine goes.. the more fuel). How would the fuel be regulated in a gravity fed setup? The venturi action of the carb?

Cheers,

Beeman

[Don]

Yes. It'll work. I didn't know about the manual vent valve in the JD's cap and blew the bottom fitting out of my old 210 gas tank, so I put a snowmobile gas tank on the hood with bungy cords and plumbed it straight to the float bowl until I got another JD tank.

With the diaphram type fuel pumps like the one on my old JD, the mechanism is actually compressing the spring in the pump and the spring pumps the fuel to give you a (relatively) constant pressure. Gravity feed should give you more than enough to fuel the tractor.

HTH
Don

[hydromike]

For comparison, 1 inch of water (we hydrogeologists call it "head" of water) equals about 0.04 psi of pressure at 4 degrees Celcius. Gasoline is 70% as dense as water. If you have a full gas tank and the needle/seat of the carb is located exactly 10" below the top of the gas level in the tank (assuming a 6" deep gas tank, and the carb is a few inches lower than it, which includes the fuel line, so you have 10" of "head"), the pressure at the needle/seat is approximately 0.3 psi for a full tank. At a half tank of gas (3" of gas in tank) you have about 0.2 psi of pressure at the needle/ seat.

From what I remember, a fuel pressure of 1 to 2 psi is more than enough to keep a float-type carb full of fuel. You can always lift the tank higher if you need more psi..

~m

[liflod]

So, if I decide to mount my gas tank a few feet above my ATV, does that mean I'll get alot more head ? Might be worth a try.

[Beeman]

Awesome! Thanks for the responses..

I'll check it out tonight and see if I can rig it that way.

[hydromike]

does that mean I'll get alot more head ? ....

Well for goodness sake raise it! RAAAIIISSSEEEE IIITTTT!

It was all a matter of time before the joke was made; I realize that...

~m

[Mike]

*Thanks for posting but I am unavailable at this time. I am currently avoiding the bad jokes in this thread*

[Beeman]

I got her running tonight. I ran the carb through the parts washer and cleaned it right up, the nosel was also clogged ontop of everything else. I drove it all around. Now I need to figure out how the mower works.. (levers for everything with no lables)