My method of purging air:
Get yourself about 20' of fuel tubing. One end goes in the tank filler neck, the other end you put whatever (banjo or whatever kind of fitting you have on the VP44). Take the banjo or whatever off the VP44, attach the hose, bump the starter (runs about 20 seconds) and watch the fuel stream going into the tank. If clear and no bubbles, you are done. If bubbles, then bump the starter again until no bubbles. Hook the VP44 back up and you know you have good fuel right at the VP44.
There are a lot of ways to do this. Put in a T in the last line going to the VP44, and on the takeoff of the T put a valve, and hook the hose there. More permanent and easier to hook up.
Bottom line, run the lp, watch the stream.
Bob Weis