Oil pumps H, M, 300, 350

[Mtjohnso]

Pulled oil pump from IH 350 utility due to low oil pressure
Pulled oil pump apart and checked the spring and pressure relief valve.
Sanded bottom plate flat using sandpaper on top of class pane. All wear marks are gone now.
Then chucked the oil pump into drill press and lowered into a 5 gallon bucket with 2 gallons of oil. Turned on drill press and if the entire bottom of oil pump is in the oil then it pumps a good flow of oil. If I just have pickup tube/screen in the oil then it does not pump.
It’s a gear oil pump. Always thought a gear pump would create a vacuum and suck oil into the pump.
What’s the real story on gear pumps? Do the create a vacuum? If not then oil has to high enough to reach above input of the oil pump.
What am I missing

 

[buzzinduzzin]

is the pickup a floating / swiveling type ? if so you could be sucking air at the swivel , if it is a fixed type one piece tube look for a hole in tube or where it attaches to pump body . A gear pump should be able to make suction even if worn some

 

[rustred]

Pulled oil pump from IH 350 utility due to low oil pressure
Pulled oil pump apart and checked the spring and pressure relief valve.
Sanded bottom plate flat using sandpaper on top of class pane. All wear marks are gone now.
Then chucked the oil pump into drill press and lowered into a 5 gallon bucket with 2 gallons of oil. Turned on drill press and if the entire bottom of oil pump is in the oil then it pumps a good flow of oil. If I just have pickup tube/screen in the oil then it does not pump.
It’s a gear oil pump. Always thought a gear pump would create a vacuum and suck oil into the pump.
What’s the real story on gear pumps? Do the create a vacuum? If not then oil has to high enough to reach above input of the oil pump.
What am I missing

If you were leaning over that pail you would have had an oil bath.

 

[DaveBN]

If the pump is like the one on my BN their needs to be a paper thin gasket between the pump body and the bottom plate. It needs to seal good but be VERY thin. We have heard of some after market gaskets that are too thick, kinda like a standard gasket. If the pickup checks ok I would look at the gasket.
Dave