1936 junior scout oil is sumping

[jn1972]

I am rebuilding a 1936 junior scout and having a problem with the oil sumping,I fill the oil tank and in about 24 hours the oil has leaked in to the sump. I have not worked on one of these oil pumps before ,I pulled it apart and it was clean and seems to fit tight any ideas ? Thanks jerry

[1950Panhead]

There is a check valve in the pump, replace the ball and spring, hit ball with punch to seat.

[jn1972]

The pump is the older style ,dry sump pump,never worked on one before I am not sure what stops the oil from sumping

[tfburke3]

The plunger to bore clearance is the only thing holding back the oil on the supply side.Since the plunger is both supply and return,maybe its going down the return line past a leaky sump valve.
Tom

[jn1972]

The plunger measures . 779 and the bore measures .783 not sure what the acceptable clearence should be or how to repair ,I will check the sump valve