Gasoline in crankcase-BS 21HP

da.bees · Oct 3, 2017

B&S Model No. 461707-0145-E3 twin cyl 21HP Origional equipment on Craftsman Lawn Tractor 917-271840
Fuel tank beneath operator's seat was obandoned and replaced by a tank on hood well above level of carburetor. Engine ran well for several months without any problem. When 1/2 gallon of fuel is poured in tank it will now go from tank to crankcase within 2 or 3 hours. Is there a way of knowing which is at fault, needle and seat or fuel pump?

steve_in_mo · Oct 3, 2017

Needle and seat. The fuel pump is supposed to allow fuel flow without the engine running.
Put a shutoff vale in when you replace the needle and seat, like a belt and suspenders.

da.bees · Oct 3, 2017

"The fuel pump is supposed to allow fuel flow without the engine running."
I don't understand what you mean by that statement. Wouldn't that have the same effect as a leaking needle & seat?

Bob · Oct 3, 2017

Fuel can always flow through the fuel pump by gravity to the carburetor. Your issue is with the carburetor float/needle and seat.

T.R.K. · Oct 3, 2017

You can check the fuel pump, disconnect the hose that goes to the engine crankcase. If its a twin cylinder, it connects to a valve cover, if its a single cylinder, it usually connects to the dipstick tube. put gas in the tank, If gas comes out the nipple on the pump, or the hose from the pump, you need a fuel pump.

It is very rarely the fuel pump.

You can also disconnect the carburetor from the manifold, hold or support it in its proper orientation like it was still on the engine. Put fuel in the tank. If fuel drips out the throat of the carburetor, the problem is the needle and seat (or the o-ring above the seat, if its a Nikki carburetor.) In some of the carburetors, the seat is not replaceable and if a needle does not fix it, you will need a new carburetor.

In the lawnmower shop, I usually specify a new carburetor, it is much more likely not to come back on me if I just replace it.

jeffcat · Oct 3, 2017

You are right on about the Niki carbs. The ones on Ebay are around $65.oo and are fabulous. Dont even bother trying to fix one. The new ones are a third revision and are great.

Mule Meat · Oct 3, 2017

AS T.R.K. stated..

Could very well be the fuel pump.

Remove the pulse tube (rubber hose from the pump to engine block) from the pump.

Let it sit awhile and look for signs of fuel running out of the pump from the pulse tube.

If you notice signs of fuel the rubber diaphragm inside of the fuel pump is bad and allowing fuel to flow into the crank case through the pulse tube once the engine is shut off..

da.bees · Oct 4, 2017

Thanks a million t.r.k. That's exactly the information I need. The condition my body has got into every minute I save from stooping over to work on things is important.

tractorguy2 · Oct 4, 2017

If you moved the fuel tank and it's now higher than the carburetor. You don't need the fuel pump. You can remove it completely.

Married2Allis · Oct 4, 2017

Oil diluted with fuel can also leak past the crank seals making you think your seals are shot.

steve_in_mo · Oct 4, 2017

No. The valves in the pump allow fuel to flow through the fuel pump whether the engine is running or not.
You'd have to take a fuel pump apart if you need visuals. With luck you might find a yourtube video.

Texasmark1 · Oct 17, 2017

Amen brother. Jeffcat speak truth! Buy carb! Will love self. Grin

⅛ Cherokee.

Mark

Gasoline in crankcase-BS 21HP

da.bees

Well-known Member

steve_in_mo

Well-known Member

da.bees

Well-known Member

Bob

Well-known Member

T.R.K.

Well-known Member

jeffcat

Well-known Member

Mule Meat

Well-known Member

da.bees

Well-known Member

tractorguy2

Well-known Member

Married2Allis

Well-known Member

steve_in_mo

Well-known Member

Texasmark1

Well-known Member

Similar threads