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Kubota B7500 fuel starved

Rob I have a B7500 that was running fine and then sputtered and stalled. It would start back up again after a few seconds and die again. I suspected a fuel issue and ran it in order to confirm. Runs for about 15-20 seconds before starting to empty the fuel filter/sediment bowl. I drained and flushed the tank, blew out all lines and checked filter (not dirty, but I backflushed anyway). Bled fuel lines at injectors and re-started. No change. Then I started checking return lines and found if I plugged the line going into the top of the filter, it ran fine. Then I reassembled that line and pulled the one adjacent to it on the top of the tank off and plugged it. That also seemed to solve the problem. So I ran it that way for a short while with no issues. Came home and found another poster has same problem and while looking at diagrams of fuel system noticed I may not have the small o-ring on top of fuel filter. Could air from the return on top of filter be getting into fuel line to pump without that o-ring in place? If not, is it ok to run with return line plugged (I'm planning on re-assembling the return from the injector to top of fuel tank and instead, plugging the return from the fuel filter). Any help appreciated. Thanks, Rob
jm. Bob First of all 80% of B fuel issues are with that filter housing. Second the early units were plumed with the return to the tank not the filter housing. And yes running without that O ring could let air go in the top of housing. I would replace the o ring and see what happens. Folks fail to realize that the return line is just as important as the supply line. If head reassure builds up on the pump it will stop operating.
Rob Jim, The tractor has two returns, one from the top of the fuel filter housing and one from the injectors. Both lead to top of the tank. I replaced the fuel filter O-rings today and I have the return from the injectors connected to the top of the tank as it should be. I also put a shut off valve in line with the return from the top of the fuel filter to the top of the tank, filled it up and put a small amount of fuel conditioner in the tank. With the shut off in the off position she runs fine. Flip it to open and the fuel filter bowl drains down and she stalls. I talked to a Kubota service tech today too. He said he suspected either a partial blockage in the line from the bottom of the tank to the fuel filter or that the plastic fuel filter body has a hairline crack somewhere. I'm inclined to agree as the filter housing stayed wet looking (although no dripping fuel) and when I pulled the fuel line from the tank from the filter housing, it drains at about half the stream size of what I'd expect. I think I'm going to have to pull the tank, flush and let it drain from the gas cap end (upside down so to speak), and I'll probably replace that fuel filter housing too. Was hoping for a temp fix that would allow me to mow my field before having to do all of that. The guy who posted on this site about 7 years ago with a similar fix said, his tractor is still running with the two returns connected to each other (bypassed the tank).
jm. Interesting and yes the plastic bowls have been know to crack. Sounds like you have really worked on the problem. Most folks give up with less effort than you have made. Please keep us informed. Where was the Kubota person you spoke with located?

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