Originally Posted by
Atimm693
It would be wise to get a hold of a service manual and study how the hydraulic system works.
It could be a lot of things, I would not spend the money on a pump until you can verify that it is not working. Could just be a problem with the lift valve, a hidden sump screen that is clogged, a stuck relief valve, etc.
The manual will outline various tests to find where the problem lies.
Allis used to partner with Simplicity, many models were the exact same with different paint, if you can't find an Allis manual, one for the corresponding Simplicity model would probably work.