Trouble With Injection Pump

I run my 1985 vw jetta turbo diesel on veggie oil. Last Feb. I installed a rebuilt injection pump. About six months ago the car , running on diesel, begins to accelerate at an idle, to about 3000 rpm all by it self. When I would switch to veggie oil it would come back to idle speed, about 1000 rpm.
Last week it all began to change. Would not cold start, on diesel, or restart when engine was up to temp.
1. Is vegetable oil destroying my pump?
2. Did I get a poor rebuild job?
3. In an injection pump, what would self-acceleration inply?

:banghead:

  veggiemo