When I installed dual fuel pumps, I just spliced into the factory fuel pump wires. Its been like this for quite a while, probably 5,000 miles and is working fine. Is it ok to splice in like that? Or should I redo it a different way? I just don't want to get stranded somewhere.

 

I'd run seperate fused relays for the pumps, that way if there's a problem you can rely on the other to get you home. One way check valves after each pump will keep fuel from trying to loop back through the other pump if one goes down also.

 

When I installed my lift pump betwee the stocker and the fuel tank, I used a splice off the power feed to the stocker as the permissive on a relay to the new pump, and a completely separate power lead straight from the battery to the new relay and then on to the new pump. That way, when the stock pump gets power, it gives the new relay permission to allow the separate power lead from the battery to run the second pump as well. Also, if anything shuts down the stock pump, the second pump follows suit immediately and I don't end up with a pump running when it shouldn't.

I also used a 30 amp inline fuse in the new lead from the battery and a 10 amp inline fuse between the relay and the new lift pump.

I have a slightly dirty ground, so sometimes I get into problems with the security system when I power down the truck... the security system relay will start clicking like mad and I can't start the truck until I cycle the door locks with the key fob. Other than that infrequently pesky issue, my system has run great.

Here is a link to the wiring diagram for my install.
https://www.ford-trucks.com/user_gal...155497&width=2

 

I had it in my head he was talking about running dual stock pumps. Something like this pic from Marty's install a few years ago.

 

Ahhh... but I don't believe that really matters in terms of how to power the pumps.

The only way I would use a splice into the stock pump's power supply would be to obtain a permissive line to a new relay which is powered by a completely new fused line from the battery. Otherwise, you could create a situation where you are demanding too much power across a wire that might not be big enough for the full load, or end up reducing the actual voltage to each of the two pumps and thereby decrease each pump motor's life expectancy. In that sense, it doesn't matter if the pumps are in parallel or series configuration... the issue is maintaining the integrity of each pump's power supply.