Any electrical whizzes here? Fuel pump issue

[Roadstir]

I recently overhauled my leaking fuel pump with new seals (and a new impeller, but that's another story).  After 4 tries I believe I finally stopped the leaking.  I bench tested the pump with a battery charger and it spun up fine, but after installing and bleeding, it would not run.  I tapped several times with a rubber mallet, but other then a few brief hums it stops.

After putting in a new battery, I measured the voltage at the pump's positive wire and got a reading of 12.5v, but when I connected both wires to the pump and nothing happened, I measured the voltage at the connection and it only read 11.4v?

What voltage should it read?
Is that drop normal?
Can the pump not operate on that lower voltage?

Thanks~

[BobH]

You shouldn't see any noticeable volt drop at the pump under normal circumstances.  You may have a poor connection at the fuse, perhaps rotate fuse 4 in the holder and see if that makes a difference.  Check the earth/ground connection, i think this is in the boot/trunk somewhere near the hinge, remove the connection and clean the metalwork and connector, before refixing.  Make sure both +ve and ground wires are clean and secure at the pump terminals.  It could be that the pump is binding, which may cause excessive current draw, and hence volt drop, although you say it worked ok on the bench?

[Kevkeller]

That drop is probably reasonable if it’s not turning but can you hook your battery directly to the pump while it’s installed and see if it turns with the gas in it?

Just to be safe I’d have the pump connected to the battery first then connect the battery at a distance.