Oil Pump Inner Rotor Orientation

[Andrew325is]

I took apart this oil pump and I forgot which way the inner rotor was installed. Does it matter which way the little black square mark is facing? I left the outer rotor attached to the spindle and the side with the mark faces towards the inside of the pump.

[alpineE30]

I think it does, the square mark on the bigger one goes towards the drive gear. also if you look at the bigger one, one side should have a crosshatched look and the other side will have circle grooves this side should have the sqaure mark. Crosshatch goes towards the housing atleast mine did. also note that there is load side wear patterns that has to correspond to the other rotor load side pattern. you might need a magnify glass to see these wear patterns, mine had two spots the size of a pen tip and the other side had the exact same wear pattern. you might only find one particular wear mark, now im talking about the face of the rotors on the inside not the tips. if you dont put it back in the same way your gonna have premature wear, its just like putting new needle bearings in an old race its gonna prematurely wear. also you should check the wear vs. the housing with feeler gauges hanyes manual gives specs but it does not say anything about the square marks or the wear patterns. my .02 cents its your call. also use fresh oil on the gears prior to putting it back together just dont drench it.

[Andrew325is]

Awesome. Thanks!