How can I restart my furnace?

Hi,
I have replaced my oil filter, yet during
the "bleeding"(priming) phase I got some air, then nice, clean oil ( for only couple of seconds) , then
a very dirty oil started to come for few seconds, then nothing at all. I checked the valves - everything was open, and before bleeding I replaced the filter, and thoroghly cleaned the filter compartment, replacd the gaskets, etc. No leaks at all.
Please help me to start the system with an advise.
Can I dis-assemble the pump and see why there is no oil flow ?
Sincerely,

Alex