The Stovebolt Site Forums The Shop Area Engine Shop Gushing fuel, can a fuel pump overload carb?

A few weeks ago the carb on my 235 suddenly started poring out fuel. A bit scary as it was dumping right onto the hot manifold and steaming.

It was a cheap China aftermarket so I figured the float was stuck open.

I swapped it out with a spare carb I had sitting around from a 235 my brother had recently purchased. I didn't rebuild it but it looked to be in very good shape and was an original supposed recently rebuilt.

So it started poring fuel all over the place too.

Can it be that I have a bad fuel pump that put too much fuel into the carb?

Any other thoughts?

Greg

Short answer - yes.

Long answer - there are lots of other possibilities.

Jon.

Greg,

Where did you find a cheap China aftermarket carb?

Tim

Greg,

I have never seen a fuel pump force a needle off the seat but Jon indicates it can be done. It's real simple to pull the top off the carburetor and pull the float off and take a look at the needle. Any modern needle would probably have a Viton tip and it should appear intact. You can drop the float into a little pan of fuel and make sure it floats.

Use a flashlight and look up into the seat. If you see any bug legs or pieces of wood jammed in it, you have found your problem. Reassemble it blow into it while holding the float up. It should seal completely.

I wouldn't condemn the fuel pump if the replacement carburetor wasn't known to be perfect in the beginning. It isn't unheard of to replace a defective item with another defective item that was in a box in the corner.

Stuart

it isn't unheard of for a fuel pump to push junk from an old gas tank into places it can't get out of - first thing is to check the fuel line filter - if you don't have one ...... why not?

Bill

I hate when those bug legs get caught up in the system!

Tim, can't remember which site I got the carb off of, it's been a year or so.

Bill, I've got filter in, didn't see anything there.

Stuart, thanks for the tip. I've got another spare that I can take apart and see how it looks.

Greg

Stuart - there is an engineered relationship in the fuel system among the buoyancy of the float, the orifice of the fuel valve seat, and the pressure supplied by the fuel pump.

A heavy (modern foam) float; the incorrect size fuel valve seat from a generic kit; or excessive fuel pump pressure can all cause fuel level variance in a carburetor. A significant amount of any of the above (or a combination) can cause fuel to run out of the carburetor.

Examples: some generic repair kits for the Carter YF have fuel valves with orifices as high as 0.110 inch when the design for the YF used on Chevrolet was about 0.086 (maximum). While more fuel can enter the carburetor, more float buoyance is required to close the valve. And there is one company out there rebuilding fuel pumps that use the philosophy that if the part fits, it will work (kind of like some look at carburetors). We have measured 19 psi from some of his pumps that should be at 3 1/2 ~ 4.

"One size fits all" might fit, but rarely performs to the level possible.

Jon.

IF YOUR FEELING LAZY as I usually am , pump a dollars worth of carb cleaner through the carb before you start taking things apart . I have an old 1955 chevy 2 ton in colorado, and every spring when i go up there my carb does the same thing . I know I know, someday I'll fix it right.