Briggs & Stratton 18HP engine problem
Got a strange problem here that normal maintenance isn't helping to clear up.
I've run the tractor a half dozen times this season already and all of a sudden, it will lose power after about 15 minutes of mowing. It will act like it's going to stall and then rev back up. A few seconds later it will do the same thing and rev back up. Eventually, it does stall. It does this even when I've stopped mowing and just sit there listening to it.
To try and correct I've done a maintenance including:
- change oil & filter
- change fuel filter
- replace fuel line
- replace air filter & pre-screen
- replace spark plug
- drain gas and try fresh gas
I've also taken apart the carburetor to look for clogs or deposits and it seems fine (although I didn't have the right tool to actually clean the injector.)
What I have noticed is that when it is running OK, you can see some gas collecting at the bottom of the fuel filter. When it starts to lose power, there is almost no gas at the bottom of the fuel filter. This is leading me to believe that the engine is stalling because of a fuel problem, but I'm not sure what else to check/replace. And I'm befuddled as to why it takes 15 minutes of mowing to cause the problem.