D15 oil pressure

I got chance to run my "new to me" D15 and have oil pressure issues. When I start it I have 20 lbs pressure, but after it runs 20 - 30 minutes the oil pressure drops to almost 0. Most of my running was at about 1/4 throttle, and the oil pressure would come up to about 8 lbs if I opened the throttle wider, sometimes, but not always. If I shut it down for 15 minutes and then restart it the oil pressure will be at about 10 lbs. I'm running 15-40 oil  in it and have a new NAPA filter on it. What is my problem?

1st thing I would do, is put a test guage on it, to verify what the other guage is reading, may be a bad guage, may not.  You won't know for sure, unless you do.  If you don't have a test guage, most any autoparts store should have a 15 dollar variety, and a couple fittings to get you going.  That's the first thing I do, when I start to see funny readings, I have replaced at least two bad guages, that had I trusted, would have spent big money fixing nothing.

I installed a new gauge today, The readings are much better. It started at 20 and then dropped. Most of the time it was around 10 lbs, dropping to 5 and the at times up to 15.

Here try this http://www.framcatalog.com/Application.aspx?b=F I think its a C159 Im not sure what series or year yours is but this has for all allis chalmers

Edited by allis restorer - 03 May 2011 at 9:23pm

There is not one thing wrong with the Napa filter unless you happen to have one that got out on the market when Wix changed the design for a short period of time. If it is 7011 Napa it is the good one. Make sure the tube is in the filter, sometimes these come out when you remove the filter and get thrown away. When I bought my D14 30 years ago I made the mistake of putting a new gauge on it and I used an eighty pounder and my pressure did just like yours. You need a gauge that is made for low pressure and it will read fine. I got me one from A&I for it and it works fine. The 80 pound gauge just won't read the low numbers that these old tractors run on. An old AC guy I know always said if an old Allis had good pressure when it started up it would be fine.JP

The D15's even the earlier ones had the full flow oil system so the oil filter on a D15 is just like a automobile filter. Are you sure that you have a D15 engine or has it been swapped with an earlier D14 engine with the back pressure design. HTH

I thought that the D-15 series 1 had the 149 cubic inch engine same as a D-14 and the old style oil system like the ca, wd, wd45. I know mine a  D-15 Series 2 with 160 cubic inch has the full flow filtering and uses a Fram PH8A filter.

The Fram site says to use a PB50 filter .