But it could also be a bad pump. I have a pump from an N14 sitting in my shed. To look at it, it looks fine. Spin the drive and the other gear spins. Stick a screw driver between the gears and the input shaft spins but the gears don't turn. I was having trouble with no oil pressure at startup, or low pressure intermittently. A Google search revealed that the gear on the drive shaft could get loose enough to slip occasionally. Replaced the pump and my oil pressure problems went away.