The engine oil pressure on my 1947? D-4, serial 6U 2831, reads really low. I bought a new Stewart Warner gage (not yet installed) but it shows only a red and a green zone, with no PSI numbers.

What is the typical pressure on this engine?

Thank you!

Fred

If I remember it was between 30-40 lbs. depending on the oil temp. & condition of the engine. There is so many things that effect the pressure from a stuck relief valve to worn pump & main bearings or another minor thing or a combination of all. In the idle position the pressure can drop quite considerbly even to 15 or 20 lbs.

Regulated to 30 psi max is what is stated in the manual.

If a stuck relief valve is the problem on one of these tractors, will the pressure be hi or lo generally?
Inquiring minds need to know.
Thanks

It can be either way but usually they stick open so then you,d experience lower pressure but it,s fairly rare for them to do it but would more likely be a worn pump or other reasons for low pressure.

I doubt it would make any difference whether you would see high or low oil pressure, but don't these engines have an inlet-throttled oil pressure control system like the D311?

If it has a small external line to the oil pump from an adjacent main bearing cap, that's what it has. Spring pressure pushes the valve open to feed the pump a full stream, and pressure from the main bearing cap pushes it shut to restrict the inlet stream of oil and lower the pressure. So the inlet valve should be wide open when you check the pump.

As wore out as these engines usually are I think it's pretty rare to hit relief pressure (or control pressure) on the oil pump and same goes for the fuel transfer pump.

"Old wrote:

As wore out as these engines usually are I think it's pretty rare to hit relief pressure (or control pressure) on the oil pump and same goes for the fuel transfer pump.

Yeah, I was kinda wondering.
But dummy me!! I been running round for last year, thinking I was hot stuff, bragging bout my 9U running 50-55-60# oil press working it. Few months back I got to playing round with my coolant temps, thermostats, flushing things, etc, etc. Finally figured out I was running too cold temps.
After I finally got the working temps on up 180 or so, oil press runs more like everyone else....35-40# And if it worked at hotter temp it would probably run less press than that.
I'm little slow, but finally figured out I ain't nothing special after all:D
But I must say, this engine does sound really good to me.....
(shhhhh....probably lay an egg & blow up in next few days...shhhh)

Hi ttman4,
It's amazing how low the oil pressure can be on these engines and doesn't seem to hurt anything. I think as long as you got flow most parts are happy;)
35-40 lb pressure is still pretty optimum if temps are right. Bearing clearance must be near new spec on your tractor. What do you have at idle?

My D4 seems to run a little less than 20 lbs when the temp gage reads 180. The temp is only 160 in the picture with the oil pressure a little above 20 lbs. Idling fast or slow seems to have little effect on the pressure.