Picture of where/how to prime the fuel pump?

[Rotary Evolution]

keep in mind that the FD has a load variable voltage output, so you may only be seeing 10v with the key on even while charging(unless you bypassed the relay system, even when bypassed it is a redundant system and usually drops a full volt from charging levels when under a load).

jumper the pump to the charging system to see what it will put out when closer to actual loaded voltage figures. and also be sure the ground strap is attached, the pump may run but it will be very slow due to poor tank grounding without it(if it even runs at all).

and of course check your math. a 255lph walbro for example would be similar to: 1 gallon = .264 liters, 255 liters X.264= 67.32 gallons per hour. 67.32/60 minutes= 1.122 gallons per minute, so it should take about 4.5 minutes to fill a 5 gallon container at maximum loaded pump efficiency. of course we want to think it's going to geyser out and fill the 5 gallon tank in 30 seconds, but that isn't the case.