B&S Mower Engine Won't Keep Running

[Dick k]

I have a Craftsman walk behind mower with a B&S engine, Model#10T802-1238-B1. Starts fine, runs strong for 1- 2 minutes, then dies like out of fuel. Fuel is burping out of gas cap. Read where this could be a faulty cap. Even though mine looked fine, replaced it and no change. If I shut it down before it runs out of fuel and let it sit for a minute, the mower will start right back up. I can repeat his cycle indefinitely but my arm is getting tired. Any thoughts?

 

[StarTech]

Can be trash blocking the fuel pickup, bad pump diaphragm, or if use the tower filter screen.

 

[DaveTN]

Welcome to the LMF! Sounds like some type of fuel starvation.

 

[frenchriverco]

Pump diaphragm or filter screen are common causes for fuel starvation. Burping out the fuel cap though, that's odd.

 

[Dick k]

Replaced the diaphragm, checked for trash in the fuel pickup, all good. Ran somewhat better after this but very rough as if fuel mixture is off. I guess I could replace the carb??

 

[frenchriverco]

After replacing the diaphragm does fuel still burp out the cap? There's pressure created by the diaphragm pump and it has to go somewhere. Usually that's through a breather tube. If that's blocked, then perhaps it is pressurizing the tank so the fuel comes out the cap.

 

[Dick k]

Yes, fuel is still burping out of the gas cap. Not sure what a breather tube is - the parts list only shows the fuel pickup and dipstick tubes.

 

[StarTech]

 

[Dick k]

Thanks, I see it now (p/n 529). It's clean. But now the thing won't start at all, won't even try, like it's out of gas. The primer bulb doesn't have the same feel as I am used to - and shouldn't I see some gas in the carb after priming the engine?

 

[StarTech]

Yes you should be able a squirt fuel everytime you press the primer into the carburetor throat.

There is a few things that can be the problem.

1. 394 could be and usually the most common
2. filter screen of 612 clogged
3. filter screen 393 clogged (not always present)
4. Primer check valve 913 may not be working. Note the primer bulb is a pain to get out at times so check the others first.

I have seen one or more of these cause problems. Also the plastic carburetor base can be warped from heat or over-tightening of the mounting screws. If warped then it is a new carburetor time.