View Full Version : Oil Pump Testing

01-06-2007, 03:49 PM
I think this was posted before, but damned if I could find it. I set up to test the flow on the oil pump from my '52 Chief and got about 50cc/minute at 1000rpm. I plugged the ports from the crankcase return and return to the tank, so I was only flowing oil from the feed port from the tank. The oil output was frothy, suggesting that air is getting in there somewhere. Is my pump OK or do I need to rebuild it? Or modify my test methods?

T. Cotten
01-06-2007, 07:22 PM

Your measurements will vary greatly with ambient temperature.

One 'rule of thumb' offered for feed rates (originating with Wilson Plank, and seconded by Gary Stark) was "a cup a minute" at 1000 rpm engine speed (500 RPM at the pumpdrive.)

A "cup" seems a bit vague at 236 cc's a minute!
It would be great to collect broader data on Indian pumps...

Plugging the return passages should have little effect upon the feed rate; You really have two separate pumps.

Problems usually arise not from the feed side, but the return is the honest concern.

The prescribed means of testing the sump pump is to let it pull oil, then air, and then measure the pressure it will push upon the return line when blocked.
30 psi has been cited as a minimum.
(Castiron model shown in attachment.)

It easy to spot a completely faulty pump. But it is a chin-scratcher to sort out the marginal from the worn-but-serviceable ones.

It would be ideal if many of us would compare notes from some sort of standardized procedure. Since it mostly takes a cheapo screwgun, and some hoses, gauges, and valves, many of us could contribute.

The highest hurdle that I have found is one of temperature control. My shop has very few days a year at a constant STP.


01-07-2007, 04:54 PM
I cobbled up my rig with an oil pressure gauge today and got 30psi on the return line when dead headed. This was with 20w50, which is what I have on hand. I think I will clean up my test rig and re-do it using 50 wt oil.

01-08-2007, 01:35 AM
I'd also like to cobble up a rig to add to the accumulated data under controlled test parameters. Hopefully this will help others make an educated guess based on a range of data.

I have two cast pumps and could easily get a few more.
I'd test for free. Then mothball the whole thing. I do not want to test oil pumps for guys. Nooooo sir, no thank-you.....

I would like to help others make an educated guess with some data. ie. how dead is dead? I figure I'll also learn a few things along the way and will be able to apply this to my own machine and possibly direct others in the future to someone who tests and rebuilds.

Good on ya guys.

01-12-2007, 07:58 PM
Well, I did my retest with 50w oil and got 70cc per minute @1000 rpm. Not a big gain. Then did a test with some swill mix I had for lathe and oil cans. Got 130cc/minute. There probably was 90w gear oil and chain and bar lube in this mix. So it looks like my pump has wear on the gears and/or the housing. I also did a reverse flow test, feeding the oil into the pump output and running the pump backwards to see if perhaps I had put the thinner metering gear in the wrong location. I got less flow, so that means I didn't screw up when I assembled the pump.

T. Cotten
01-12-2007, 08:44 PM

My own results for late pumps averaged around two ounces or ~ 60 cc's per minute in the feed side. That's a demitasse cup I guess.

So yes, we need some standardization, although I feel your feed side is probably adequate. (Besides gears, you can try just lapping the cover plate, and then compare your readings.)

The increased volume with high viscosity is very interesting!

If we can all use straight 50 wt at 60F to 70F, it would certainly help any future comparisons make sense.

And rpm is an issue since not all screwguns turn 500 rpm (to give an effective 1000 rpm at the pump drive).

I have a hand tachometer for accurate measurement, and most screwguns I find in the alleys turn faster. Variety will be great for plotting meaningfull curves, but we still need a baseline that we all can reproduce: Like a $10 Harbor Freight special, but unfortunately, they have discontinued the slow lower-voltage models in favor of more power.

I have four castiron pumps and one aluminum, and my own '34, to document.
And a '31? and '32? to figger out.

But I haven't worked out the temperature control aspect.


01-15-2007, 06:58 PM
Played around today some more. Was just curious, so I tried some ATF (Dexron-Mercon). Grabbed it out of the cold part of the shop, so it was around 35F. Got 120cc/ minute and no frothing of the output. Grabbed the 50w that was also out there and cold 50w only got me 30cc/ minute. About half what I got at 65F.