Yeah, I've found the pumps are hit or miss.
Some I've done without help, and others need a little kick to get going.
This last one I did needed a little pressure on the inlet side to get it primed & pumping.
I don't think these in tank pumps are really designed to siphon/vacuum very well.
Vega Joe wrote: Plus if you hook it up turn the key on then climb under the car to blow in the vent wouldn't it already be primed and flowing by then ??? I'm not flaming , just trying to learn .
What I meant is engine's not running yet, but key in ON position to supply power to the pump. If the tank is out of the car, but under its mounting location, you can connect the wire plug and access the vent hose/etc from the top. Sorry for the confusion.