I have a Janitrol Furnace that will not start up.

I pulled of the tube from the draft inducer to the pressure switch. I sucked on the tube and the furnace fired up.

So I checked the voltage going to the draft inducer, it read only 6v ac.

Where do I go from here?

You need to trace the wiring back to where it came from. If it terminates on a circuit board check the voltage there.

I traced the wires back. The white terminated at a small white box next to the circuit board. The black terminated at the circuit board. The voltage from these two terminals was 16V.

I might have made matters worse, when I was tracing the wires back, I found where the white wire went, I assumed that the black wire attached next to it was the black wire from the draft inducer. I went to measure the voltage from these two terminals and I heard a pop. I blew the circuit in the breaker box. The fuse on the circuit board was fine. Once I reset the breaker, I measured the voltage across the correct terminals and I also measured the voltage at the fan( it was still 6V)

If the board was not bad from the start your chances are better now. It takes very little of a voltage spike(or direct short) to take out a control board. Did you check to see if the blower or any thing els will work now.