David Brown 885 diesel fuel in crankcase - followup

About a year ago I posted a question about diesel fuel in the crankcase of my 885:

https://forums.yesterdaystractors.com/viewtopic.php?t=1523185&highlight=

Eventually I decided to have the local Case dealer look at it and they felt replacing the lift pump would be the place to start, much as suggested in my first thread. The tractor hasn't had much use until this fall running a grain auger at harvest. The oil level hadn't come up so I thought the problem was fixed. The tractor was run quite a bit at harvest and once again it would run rough, smoke black exhaust - and the oil level had risen quite a bit on the dipstick - same as before. Also when shutting the tractor down when it was acting up, it would sometimes keep running longer than usual and sometimes speeded up a bit.

In discussing it with the dealer they felt, like some of the replies in my first thread, that it might be a seal in the injection pump. But after their mechanic looked at it again and thought it over, he thought fuel might be leaking past the thermostart (p/N K928523). Until harvest there was only about a quarter tank of fuel but I filled it before harvest so the fuel level was higher than the thermostart.

So my question is: Is this a possible cause of my trouble? I think he might have hit on something but wanted to check with the experts here on YT. Thanks for any suggestions.
 
My experience with DB units is almost zero so I can offer very little good advice on this problem. This idea of a problem with the thermostart unit sounds logical and
would be so very easy to trouble shoot. Simply disconnect the fuel line to the unit and operate the tractor for awhile. If your problem goes away you know it is the unit,
if not you know it is OK and the trouble is something else, Rod.
 
Thermostart unit could do it, start by removing and capping
the line as Rod said. If oil still rises then injection pump drive
seal is next culprit. I see that seal fail over time a lot lately on
pumps I tear down for repair.
 

The Case mechanic was out this afternoon and we capped off the fuel line to the thermostart, and disconnected the wire to it as well. He noticed after starting the tractor that there was still power to the thermostart which might be caused by the ignition switch which is quite worn. I'm going to install a new switch, drain the crankcase which has quite a bit of diesel in it, and fill with new oil and filter. I'll run it and see if the oil level stays normal. If not I guess the next step will be replacing the seal in the injection pump.

Thanks for the replies.
 

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