Oliver Super 88 Oil thining low oil pressure (Fuel?)

I have a 88 with a super 88 diesel in it, the motor is fresh with only twenty hours on it tops. I was farming with it and it started losing oil pressure. I took it back changed oil and filters, took it out on the field. The oil pressure was fine on start up after ten minutes the oil pressure started dropping again. I checked oil and it appears ruined after 15 minutes. It's shell rotella 15-40. Additionally when I put the new oil it I filled it to 3/8" under the full mark, after 15 minutes the oil level was 3/8" over. Oil is not milky so it leads me to believe it's fuel but I can't really smell it on the dipstick. The injection pump was rebuilt less than a year ago, its a Roosa-master DB2 I believe. I don't think the front seal on the injection pump is leaking fuel in because its all new. The lift pump is original so I believe it is the problem. I pulled it off and pumped it by hand I can't see it leaking. This leads me to my question, is it possible for it the leak even if I cant pump it by hand to make it leak? Are there any other ideas on whats wrong? One more question I pulled out the oil pressure regulator spring, when I removed the nut all I got was a spring is that normal? (Spring looked fine.) Thanks guys, Sorry for the length I just wanted to give you all the details.
Mike

Injector sleeve seals

How do I go about test/replacing those?
Thanks Mike

Most had the American Bosch PSB pump, but the later Roosa DB could be on too. If the DB rear umbrella shaft seal is rolled forward it will leak. Another place could be the OD of the brass shaft pilot tube. They fit loose in the housing, if it was replaced the correct way is with the two part epoxy mix. I've seen them leak if Loctite was used, it does not seal as well.

(quoted from post at 03:15:01 06/17/14) If the DB rear umbrella shaft seal is rolled forward it will leak. Another place could be the OD of the brass shaft pilot tube. They fit loose in the housing, if it was replaced the correct way is with the two part epoxy mix. I've seen them leak if Loctite was used, it does not seal as well.

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It is a DB2 I believe, it's off a 1800 or 1850 I think. How difficult is it to change the umbrella seal? The pump was rebuilt less then a year ago. Will I be able to see if it is rolled forward if I just remove it and look at the end of the pump?
Mike

bump