This may sound stupid but 3 years ago i put a new pump on my 4wd saff
i spent ages trying to get it to prime
checked it was getting power etc...
Gave my mechanic m8 a ring he gets under the car swapped to wires round for like 1 second so it rang backwards??
then put em back round the right way and the damm thing primed up straight away
I have no idea why he knew it would worked but it did