Oil Pump Problems
 

I'm beginning to collect waste oils for my diesel and didn't want the hassle of buying a new oil pump which is several hundred dollars. So instead I ordered a 350 Chevy oil pump and modified it with JB weld to where it had an intake and output. I then received a motor from my friend for free, it's a large century motor meant to power pools and spas. I believe it's a single phase 1.75 hp and it spins at 3750rpm. The other day I was able to mount the motor and pump on a stand and tried to test it out and all the pump did was push air out of the intake side. I had the intake and the output both submerged in oil and it wouldnt pickup up any, I'm also confused where it sucked the air from off both hoses were submerged. I then tried the pump out by attaching a drill to it the shaft is 1/2in so it fit perfectly and it worked perfectly. The drill and the pump spin the same way so it's not spinning the wrong direction. Could it possibly be that the motor is to big for the pump? Because of running out of ideas and solutions. Thanks- Frank

A 3450 RPM single phase motor will run at 3599 RPM with no load, and drop down to 3450 RPM as the load increases. That's in the US where we have 60 Hz power. The oil pumps I'm familiar with all run at half engine speed, so your pump thinks it's on an engine running 7000 RPM. It certainly ought to be doing something at that speed.

Was it primed when you ran it with the motor? You know it was primed when you ran it with the drill, so did you try running it on the motor after you ran it with the drill?

You can really feel it when the drill driven oil pumps starts producing flow. As long as you have the rotation in the right direction and don't have too much vertical distance to pull the oil it's pretty bulletproof.

regards
mech

a check valve at the end of the intake hose may be useful here, you really don't want to prime it more often than necessary.

as long as you're not pressurizing the oil, it shouldn't be a huge drag on any reasonable motor. just moving oil isn't too bad, assuming it isn't super thick, but once you start trying to pressurize it, effort required increases immensely.