lawn mower fuel leaking out around gas cap, but gasket is intact

[oldfella1962]

Okay, I have a push lawn mower with a Briggs & Stratton 300 engine that has a problem. While it's running, fuel starts coming out from around the gas cap. The tank is NOT overfilled, that's the first thing I checked. The gasket inside the cap is intact and seated properly, and the cap tightens down solidly. The fuel tank itself is tightened down tight to the engine frame. Is it likely to be the cap or the fuel tank itself, or something different altogether?

Also if it is a cap, and I want to replace it, how do you get the cap out of the tank? In other words it's attached to the inside of the tank on a long piece of plastic.
Any thoughts?

 

[Milkman]

Okay, I have a push lawn mower with a Briggs & Stratton 300 engine that has a problem. While it's running, fuel starts coming out from around the gas cap. The tank is NOT overfilled, that's the first thing I checked. The gasket inside the cap is intact and seated properly, and the cap tightens down solidly. The fuel tank itself is tightened down tight to the engine frame. Is it likely to be the cap or the fuel tank itself, or something different altogether?

Also if it is a cap, and I want to replace it, how do you get the cap out of the tank? In other words it's attached to the inside of the tank on a long piece of plastic.
Any thoughts?

Pictures please

 

[GeorgiaGlockMan]

The cap probably has a plastic "fork" or toggle bar. Should be able to pull it out without breaking it.

Take the gas tank off to inspect it better. Maybe do a leak test with water.

Good luck.

Eta - just looked at my lawn mower. It has a ball chain and a metal bar on the has cap as a keeper. Reach in the tank,, grab the bar end with some hemostats or needle nose players, turn bar sideways and pull it out.

 

[oldfella1962]

Pictures please

I don't have a smart phone nor a camera at the ready. But somebody here just said how to get the cap out of the tank. Luckily I have an identical lawn mower (I have one mower, my son who lives 1/2 hour away has the other) so I can swap caps to see if the problem is indeed the cap. If it's the actual fuel tank (also easy to swap) a new one is half the price of an entire lawn mower! But for now I can get the cap off the tank and look it over more closely, or even do a leak test.

 

[oldfella1962]

Hmm, sounds maybe similar to our situation, maybe pressure buildup inside tank?

Wifey’s like new push mower (Briggs) blew the gas cap off while she was cutting this weekend, and at same time dark smoke came from around engine front.

Pressure buildup? I never thought of that. No dark smoke though when the mower runs. Well as soon as my son & myself get some free time we can swap caps/tanks and see where our problem is.