855d loader

I am having fuel problems. Machine will work great for 20 minutes then run out of fuel. I take the filters off and fill with fuel and pump the fuel pump with the bleeder just above the filters open after air is out close bleeder and pump till everything is full and machine starts up and will work for another 15 or20 minutes and it does it over and over. I have replaced the fuel pump fuel filters rubber hoses and blew air back through lines to make sure not plugged in tank. Each time it quits I can take the hose off at the pump and have a full stream of fuel. Each time this happens both filters will be about empty. Doesnt happen when just moving machine from place to place only when working hard. I took the vent out of the filler neck on the tank and tried running with it out didn't make any difference. Any help would be greatly appreciated. Thanks pumpman

not familiar with your loader but i had that problem with my D75S3 and it has a float tank between the fuel tank and the injector pump. it had a piece of an o-ring under the float tank needle and seat like to have never found it. mite be worth a look

Have you drained the tank and inspected yet? In a incident years ago I had a utility boom truck that did as this, had a floater in the tank that when worked hard and stirred up would float over the tank outlet shutting off fuel flow. Engine stopped suction stopped floater moved away until got running again them would do it again in a period of time but never right off and always had fuel available when I checked the tank outlet save the one time I caught it.