Lift pump dropping fuel

[Wheelie]

Hi would anyone have a reason why diesel is dropping down in the lift pump glass bowl,it's full when engine is running but diesel level drops down to half way about 5 mins after stopping engine,it starts fine and doesn't seem to be any air in system when running,it's a new lift pump and was fine for a few months,and doesn't look like there's a leak anywhere,thanks

[db2d]

Can you please give the tractor model.
If the valves in the lift pump are defective the fuel can return to the fuel tank if the tanks are under slung. The diaphragm can also be defective. If the pump is defective fuel can leak into the engine oil.

[starider]

Hi,one thing to check,make sure the filter glass bowl is seating properly i.e. the rubber sealing ring is OK and that the but knurled nut is tight[do not over tighten]...................starider

[Wheelie]

It's a 1490,ok will check that again thanks,it does seem to drop to the level where the diesel enters inside the glass bowl itself

[Wheelie]

Just some more info,I don't know if this is usual but when the bowl was full I loosened the diesel intake pipe at the lift pump and the diesel ran out down to the level it was dropping to,maybe it would do that anyway?

[ollek]

The valve on the intake side of the lift pump should keep the fuel in the bowl, even if the pump intake pipe is loosened. Dirt from the fuel tank can get its way to the lift pump and get jammed in the intake valve, making the fuel leaking back into the tank.

[Wheelie]

Ah right thanks for that sounds like the problem, because there was some dirt in the bowl but never seen it happen before,took off bowl and cleaned around sure see what happens this time, would that lead to air getting into the system though?because it will start and run no problem

[ollek]

Leaking lift pump valves will not let any air into the system.

[Wheelie]

Right thats good anyway,might just replace with another new one sure,don't want any leaks into the oil thanks good info