Turn oil pump by hand, how easy?

I installed the oil pump last night (I’m reusing) and was turning the pulley using the wrench after tightening the bolt and it wasn’t as smooth as I would have expected. I can’t turn it by hand and the chain isn’t adding any notable resistance.

Does that seem normal? Should it be easy to turn?

 

I went ahead and ordered a new pump. A little painful to have to buy at this point in the build (what about it makes it 7 times the cost of a water pump?).

The engine this pump came from had rod knock and I didn’t want to risk reusing it, given what appears to be non-smooth operation.

 

An oil pump has resistance because it is a pump. What you're feeling is the pump pushing internally. There are gear pumps and gear rotor pumps. I'm fairly certain based on it's design the speed pump is a gear pump.

Essentially there is a spring inside the pump to bleed pressure back off so the pressure doesnt sky rocket as the pump spins up. You want a given amount of oil flow at X rpm. I would be worried about the oil pump having no resistance at all.

But if the pump came from an engine with a rod knock you're better off replacing it as you already plan on doing. Metal going through the engine will wear oil pumps internally.

 

Thanks for filling in details, I appreciate it! It hadn’t occurred to me to replace the oil pump until I noticed the resistance, and after considering that the rod bearing was toast I became concerned that maybe the pump was failing and that may have caused the bearing issue. Even if it’s fine, at least it won’t be on my mind anymore

 

For anyone interested, I got a new oil pump and can easily turn it with my fingers. The oil pump I had planned on reusing cannot be turned by hand at all. So I’m glad I got the new pump

 

You decided correctly.
The gear oil pump should under no circumstances feel in any way hard to turn by hand. You should open the old one you replaced, inspect, and post pics for educational purposes. Oil pump failures notwithstanding foreign debris getting sucked in are very rare if not unheard of.

 

Good idea! I’ll do that.