Just converted from bottom supply to top of tank supply to avoid sludge in bottom of tank,but can't get feul to pull from top. Have bled but nothing,

One or 2 pipe system?

Is the furnace above or below the oil tank?

Belowit turns out that I did not need the return pipe back to the tank. Once I removed and caped it off at the burner fuel began to flow. Question is why did everyone tell me that I needed the twin pipe setup.

Who is everyone?

Both one and two pipe systems have there place of usage. It all depends upon where the oil tank is located in relationship to the oil burner.