Can an open Fuel Shut Off Valve reduce fuel flow?

Poulan Pro 300 EX, B&S 18.5HP, 42" Cut, Model PB18542LT, Product 960420088 with a Briggs & Stratton 18.5 500cc I/C Model 31N707, Type 0301 B1, Code 0903162D, Engine.

Recently purchased several years old, riding mower already had a large generic fuel filter (I have changed oil, blades, deck belt, air/pre filter, spark plug and greased it). I added a B&S fuel shut off valve (searching for new fuel filter). . The shut off valve is between the carb and the fuel filter. The fuel filter is between the shut off valve and the fuel tank. Yesterday, after mowing, I put it in the fastest gear it has (6th gear) with the blades disengaged as I was driving back to the garage on level ground. The engine began to sputter as if it was running out of gas or had water in the fuel. I stopped and found that I still had about 1 inch level of gas in the tank. I slowed down and it stopped sputtering.

Does my engine have a fuel pump or is it gravity fed? If it is gravity fed, is the open shut off valve reducing flow when there is less gas in the tank? Should I remove the fuel shut off valve? Or should I look eles where for the issue?.

Your engine should have a fuel pump mounted on the side of the engine cover. It will have three hoses attached. One from the tank, one goes to the carb and a third pulse line coming from the engine. Do you have the correct Briggs fuel filter for use with a fuel pump. Should be a 75 micron filter for use with pumps.

Next time it acts up, take notice of the fuel level in the fuel tank. If the fuel level is low like it is now and the problem is evident, stop the mower right there and go get your fuel can and fill the tank at least half way full or more. Then try the same route and gear position to see if the problem goes away and that will tell you if the fuel tank level can cause that problem.

With only one inch of fuel in the tank it is possible that the fuel is sloshing around side to side and allowing the gravity pick up tube to be exposed which could allow air into the fuel system causing the problem you describe.

For my B&S engine model and type numbers, Partstree shows a diagram for two difference types of fuel pumps for my engine. Therefore, I pulled the engine cover off and searched for the fuel pump. Fuel tank hose goes directly to carb. The only other exposed hose on engine is on the other side of carb and it is some kind of pvc/vent line that goes into engine near flywheel.

I called Poulan Pro tech support (which is a business called engine wharehouse). Tech walked me through it and the tech concluded that my engine does not have a fuel pump?? I asked if I should install one and he said without the pump there is less to go wrong and he would not install one so long as the fuel tank is higher than the carb (it is). He commented that the shut off valve (opened) would not reduce flow but too small of a fuel filter would cause problems. I will install a new fuel filter when I find the equivilant of a 394358 or bigger? Thanks for the comments.

Update:

Ran it until fuel level in tank was down to 1/4 of an inch and it still ran great at its fastest speed with max throttle.
However, it was either the wrong fuel filter (mower had a pump feed filter instead of a required gravity feed filter) or it was a sticking choke that I found and fixed and or the fact that the throttle is not aligned with the speed level icons on the dash. Thanks for the help.

In my case, the shut off valve did not reduce fuel flow. See pic below of my gravity feed fuel system with gas tank under the hood, new B&S disk fuel filter, new B&S shut off valve with the awesome B&S 18.5hp engine :biggrin: