Rotors in the oil pump.

[caoverton]

I don't understand the mechanics of the oil pump.

'51 dodge B3..218 engine.

I have to fix a leak at the oil pump cover plate. So when I took the cover plate off, the outer rotor fell out. I see there is a slot grooved in the outside of the outer rotor, like a woodruff key might fit in there, but can't see inside the pump where it would engage with another slot.

Does the outer rotor spin as the inner is spun with the camshaft? Or is the outer supposed to be fixed with the woodruff key and the inner spins inside it?

I am so new to this thing. I don't understand the mechanics of it.

[Merle Coggins]

It is called a gerotor pump, and yes, the outer rotor spins with the internal rotor. Check this out.

http://www.pumpschool.com/principles/gerotor.htm

Also, when you reassemble it, pack the rotor space with a light asembly grease, or Vasoline, before reinstalling the cover. If you don't it won't be able to draw enough vaccume to pull up the oil from your pan. If you pack it, that will remove the air and it'll pump right away. And a light assembly lube will break down in the oil without any problems.

Merle

[caoverton]

Thanks Merle, now I get it..

How much do I pack in there? Enough to fill the whole pump shaft?

[Dave72dt]

Yes, pack it full.