BOBCAT 773 G won't stay running

[jss]

I have a 773G use to run great now it seems to be sucking air this is what I've done so far any help would be appreciated. Replaced fuel lines, pickup tube and a new fuel filter. Sometimes it will run good say a couple of hours then all of a sudden it will die and the fuel filter is full of air. Seems like if you rough house it, it will die even faster. Any one with any ideas what I might have missed? I've been fooling around with this for several weeks. Thanks

 

[Tazza]

Have you tried hooking it up direct to to a bottle of fuel to eliminate the entire fuel line from the engine to the fuel tank?

 

[jss]

Have you tried hooking it up direct to to a bottle of fuel to eliminate the entire fuel line from the engine to the fuel tank?

Yes it ran fine for about 1/2 hour and it would still do the same thing--run for awhile then die

 

[Tazza]

Yes it ran fine for about 1/2 hour and it would still do the same thing--run for awhile then die

Ok, it has to be drawing in air. I'd start by checking that the bleed screw on the pump is closed, this can cause issues if its not fully closed. Then i'd look at the lift pump, if its failing it could draw in air causing problems but usually the oil level increases as diesel fuel enters the engine as it leaks past the lift pump.
There is no other reason for it to loose prime like that. If it starts and runs it cant be the pump or injectors, it has to be something before that causing the fuel to not get there without air bubbles.