I installed an electric tongue jack and connected it to the factory trailer plug 20 amp pin (1:00 position on plug) I keep blowing fuses on the tryck breaker if there's any excessive weight being lifted. (If the ball doesn't release right away) If I hook the jack up to a jumper cable it seems to do fine. Do I need to homerun a power line direct from the truck battery to the jack?

Sounds like you are pulling too may Amps across that circuit. I think your safest bet is to do as you described.

See if the paperwork for the jack shows a max amp load. If you're lucky, it might show something more than 20 and explain blowing the fuse. If you're REALLY lucky it will be under 30 and you can just put a 30amp fuse in (and hopefully not fry the wire).

Thanks.....I was afraid of that. Spent an hour today trying to get the stupid trailer off the truck by myself while the wife and Daughter were waiting for me at the dock. It should have been a 2 minute deal. Had to pull the truck jack out and it finally came of the ball.

I as thinking of a 30 amp and just keeping my hand on the wire form the jack. There's a slow-blow fuse on the wire to the jack. I'll check the amperage. If not, Sdwayz said he'd run a new wire for me.

Kevin, I don't work for cheap. You should see me wire a PBX.

You could install a battery on the trailer and wire your 12v source from the truck to that battery. Most ele trailer jacks use the extra battery due to the high amp draw (@25-50) The higher you rase the trailer and increase load, the amps will go up also. If the truck dose not release you will max out the jack. Try to rock the truck once you see it start to load up from lifting the truck.
Good luck.