I have an Allis HD-4 crawler that I just bought, it was sitting in a garage for about 25 or 30 years. I started working on it, but can't get any fuel through the pump. I have good fuel flow to the pump inlet, but it won't bleed. I took off the end cap to check the transfer pump and all seems ok there. Anyone have any experience working on these pumps? I really don't know where to go from here, other than taking the pump off and having it rebuilt.