Baffling engine issue - runs for 6 minutes, dies, but then starts right back up

[Tbone0106]

I know this has a metal 90 degree elbow with a shutoff valve. I cleaned out the tank as thoroughly as possible while troubleshooting everything last time, and also used a small pipe cleaner (the kind kids use in school projects) around that elbow. At this point willing to try about anything.

Would you be able to take a picture of that when you have a chance? I'm not quite following what you did and how it relates to this design. Thanks!

I'm not sure what you want a picture of. What I did to fix the problem is all inside the fuel tank, and it would be pretty tricky for me to get pictures of that.

The 90-degree elbow I'm talking about is plain brass, without a shutoff valve. It is mounted in a rubber grommet in the top of the plastic fuel tank. Because its inside diameter is considerably smaller than either the pickup tube or the fuel line, it is a fairly obvious choke point in the fuel system. And since the factory pickup tube is unfiltered, I removed it and replaced it with a length of standard fuel hose with a filter on the bottom end, weighted with a couple of old steel nuts. There are pickup filters made for some older Stihl chainsaws that fit standard 1/4" fuel hose perfectly.

 

[BWC4WIFE]

Gas Cap
Same issue — well similar. My new (Chinese) carb musta had some debris in the main jet. I soaked it for 20min in CarbCleaner and blew it out — fixed one issue.
But running for a bit and then dying that’s the gas tank creating a vacuum bc it’s not venting. When it starts to slow down unscrew the cap a little and it’ll pick back up. But you can only cheat it for so long

 

[wesw]

Mine wasn't gas cap - as mentioned it's not a vented cap design, pulls air through a hose that's filtered from air filter.

I think I have finally fixed the issue. @bertsmobile1 had suggested it was fuel related early on. I ended up replacing the screw in shut-off valve and the problems largely went away. I couldn't find anything in particular wrong with the old one when I tore it apart, but I did notice the new one had an integrated filter, and of course the rubber washers were in much better shape. It's a pretty poor design that's being used in the valves, the fuel takes so many right turns it's amazing it makes it anywhere sometimes.