2T Cylinders Filling With Fuel When Not Used

[Bailes1992]

I have three small 2T OPE engines. A 25cc strimmer, 21cc rotavator and a 50cc post-hole auger/drill.

All 3 engines, if stored for more than a day or two with fuel in the tank will somehow migrate a significant amount of fuel from the tank into the cylinder resulting in a hydrolock situation when you go to crank it.

Is this normal for 2T equipment? Or am I doing something wrong? I now empty all the tanks after use and run the engines till they stall. But it would be good to know if something was wrong.

 

[Propflux01]

Probably the gas tank pressurizing from heat, forcing fuel into the cylinders since you say it’s all three. Try leaving the gas cap slightly looser and see if it doesn’t stop it.

 

[DriveHard]

How are they stored? Can you put the gas tank down from the carb?
Do you use them on cool days, then store them in a hot storage area/garage?
Do you fuel them up before storage with cool fuel?

 

[Bailes1992]

I think you've hit the nail on the head there. Something I didn't consider the swings in temperature that probably go on every day in my shed as it's usually in the sun. I'll stick to draining the tanks after use. It's no hardship really.

 

[Warlord]

Are you sure that’s whats happening? Millions of two stroke tools sit in sheds without issue but all three of yours somehow flood during storage? The fuel caps generally have some sort of vent to prevent over pressure and vacuum situations. Maybe the flooding occurs when you’re trying to start them.

 

[samven]

I am not sure how the gas is getting into the cylinder. A 2 stroke draws gas into the crankcase and at the bottom of the piston stroke gas/air is drawen into the cylinder from there not from the carb. So the crankcase must be filling with fuel. If you have those little primer bulbs you will notice that the fuel is drawn up to the carb and overflow is directed back to the gas tank. On older units the gas cap had a vent so the tank could breath but newer ones may have a 1 way valve so pressure is pushing the gas out, probably and EPA thing.

 

[Greasymechtech]

Buy some fuel shut off valves. Should be able to get them at any small engine shop. For example,

Briggs & Stratton 698183 Fuel Shut Off Valve

Keep it Running - Keep it Genuine. Help keep your outdoor power equipment running at peak performance by ordering Briggs & Stratton replacement and maintenance parts. You can find the right part you need including carburetors, air filters, spark plugs, tune-up kits and other engine repair parts...

shop.briggsandstratton.com

Oregon Inline Fuel Shut Off 1/4" Ball Valve | Oregon Products

www.oregonproducts.com

Filters and fuel valves are some things that we all should consider.

 

[JTK]

Like said above, bad gas cap check valves (duck bill valves) or storing the unit wrong can do this.

 

[JohnnyG]

Probably the gas tank pressurizing from heat, forcing fuel into the cylinders since you say it’s all three. Try leaving the gas cap slightly looser and see if it doesn’t stop it.

Fuel tanks are normally vented. Now if that vent is plugged, or has one of those "duck bill" vent valves, you may be correct.

 

[JTK]

Fuel tanks are normally vented. Now if that vent is plugged, or has one of those "duck bill" vent valves, you may be correct.

Thinking about this further, you're right on. The caps with the duck bill are designed to hold pressure in the fuel tank. I'm not sure how those systems relieve pressure.

 

[Fordiesel69]

Check the metering diaphrams for stiffness. If they are stiff they will hold needle open and cause he pressurized fuel to travel into the engine.