Runs for 10 minutes, then fuel supply slows

[RayCo]

I have a BX that recently started running a bit choppy and sputtering after using it for 10-15 minutes. After a bit of poking around, I determined a blockage of some sort exists either in the fuel tank or the line coming off the tank, prior to the first fuel filter. When I disconnected the fuel line before the first filter, the fuel slowly dribbled out. I shot some compressed air up the line, and the fuel poured out as expected. It was good for a while, but then the problem returned. I did the same thing again. Since that was just treating the symptom, it of course occurred again. I've since cut a 2.5" hole in the top of my tank so that I can see and access the side of the tank where the fuel exits. Haven't seen anything obvious, but this weekend I'll drain it again and get in there with a vacuum, now that I have this access port.

BUT, THE QUESTION, which is really more of a mystery, is this. I can operate the tractor for 10-15 minutes just fine, and then it'll start sputtering and die. If I shut it off and come back 30 minutes later, it still sputters. If, however, I come back 24 hours later, it'll go back to running fine for 10-15 minutes before sputtering out again. I can't think of any sort of obstruction that would decide to remove itself overnight and wait until the next day to return. Typically if something is clogged up, short of touching Jesus's robe, I don't expect any miraculous healing here like has been occurring. Can anyone think of something that would clog a fuel line and then miraculously heal itself overnight, repeatedly? This has been happening for a few weeks.

Like I said, I believe the fuel restriction to be in the tank or in the first line coming out, but now I'm wondering if there could be a secondary condition further down the line that reveals itself after the engine reaches full operating temperature.

 

[Rosher18]

Are you still running with the 2.5" hole in the tank? This sounds a lot like a plugged tank vent causing vacuum to develop in the tank as fuel is withdrawn, limiting flow until it fails to run. If still running with the 2.5" hole, that theory is null.

Maybe it's a combination. You could be sucking air through some part of the fuel system due to the limited flow from the tank, especially between the first filter and the injection pump. If you're getting any kind of air in your fuel system, it'll run like total junk until the air is worked out.

 

[TripleS]

I think its your fuel cap or if the tank has a vent tube check it.

 

[jaxs]

"
" When I disconnected the fuel line before the first filter, the fuel slowly dribbled out. I shot some compressed air up the line, and the fuel poured out as expected. It was good for a while, but then the problem returned." Vacuum has already been discussed and I assume you removed tank cap while line was disconnected so that rules that out. That only leaves a screen inside tank clogging with debris. Air pushes debris away from screen but it sucks back as fuel flows out. I would disconnect line as you did above and extend it with rubber hose to drain all fuel from tank into a can. When flow slows,blast it with air until tank is empty. Removing line and fitting from tank should bring screen out with them. Assess condition of screen and clean or replace as required. If line can be reconnected to tank without screen in place I would pour fuel through tank to flush out trash and catch in can. Either refill with fresh fuel or "polish fuel" before returning it to tank.

 

[RayCo]

Not much has changed from teenage years. Gotta clean the screen.

 

[JWR]

Problems similar to this have been posted on TBN dozens of times over the last few years. There is the clogged filler cap to inspect, the leaf floating in the tank that finds it's way to the outlet, the elusive crud in a filter, air leaks in lines, etc. The OP said "If, however, I come back 24 hours later, it'll go back to running fine for 10-15 minutes before sputtering out again." That tends toward fuel seeping in over time to fill the lift pump and filters. In other words the obstruction is not "removing itself overnight" but instead the fuel is slowing seeping through the normal path and it is taking hours for enough to seep through for a few minutes of running. That little engine will run quite a few minutes on the tiny amount of fuel in the lines and the filters, especially when you may have a trickle of flow coming all the time. Something hanging around in the lift pump maybe ?

I often suggest that you get an "IV bag" like from a hospital or medical supply house (or fabricate your own in whatever way) and temporarily put the IV Bag in gravity feeding fuel and see how it runs. Start right before the first filter. Just keep moving the feeding point of the IV bag back toward the tank until ypou finally isolate the obstruction. No matter what the obstruction is it is a game changer to find out exactly WHERE it is.

 

[RayCo]

Brilliant stuff, JWR. Oddly, I'm pretty sure we still have IV bags around my house from when my wife ran a ferret shelter in the 90s, so I'll use a literal IV bag just for the fun of it. Thanks!

 

[Maineuropa]

Clean everything in your fuel system including the tank itself. Replace all filters. I use a 6 gallon outboard tank of gas for my “IV” on the gas machines. The diesel 955 Deere has a crud collection pocket at the very bottom of the tank, below the fuel suction line so it is less likely to get into the fuel for example; no amount of air will fix that.

 

[RayCo]

Lots of cleaning, and so far so good. I love that.