John....
If the pump loses it's prime....it can be difficult to start.
This is why the guy you bought it from said to open the throttle wide and spin it.

Well.....that will not work most of the time either unless fuel is already at the pump inlet.
I use a YS check valve on the tank overflow to prevent fuel spills so that when the tank fills, close the overflow line, then continue to pump for about 6 or 8 seconds.
This will pump up some pressure in the tank forcing fuel to the pump inlet.
THEN...spin the engine at WOT for about 8 seconds, close the throttle, crack the idle and it will start instantly.
I do this before every flight.
Using this method, there is no problem starting even if the engine is hot....I can land, taxi to the pits, refuel and restart immediately without problem.
This is not my technique....everyone I know does it this way.