Fuel in the engine oil, idles higher than normal

[otto huber]

Hello,

I have a '79 240D with polymerised engine oil as a result of using a one tank SVO set up. I'm going to go back to just using biodiesel, but because of the high idle, I'm afraid that there is permanant damage to the IP.
I plan on changing the lift pump and the metal piece it taps into which mounts on to the side of the IP. I've got an extra IP that I pulled out of a yard. Is this the right place to start?
I changed the engine oil, and it gooped up pretty quick. I'll change the oil again when I replace the lift pump. Any suggestions would be greatly appreciated. Thanks,

Otto