Double pumper install questions

[Fenrir]

I've got a hotwired 340 installed in my car now and have a double pumper I'm about to install. I'm assuming it's fairly straightforward installing it with the hotwire kit already there but for the second pump and I have some questions. I already have the hobbs switch and have a trunk mounted battery. Would it be acceptable to wire the second pump from the battery instead of running another hotwire up to the alternator? Are all fuel pump relays equal or is there a better/more reliable brand?

 

[Heath]

I bought one from radio shack along time ago. Can't remember the number.

 

[Fenrir]

Any other thoughts?

 

[SPOT MY 6]

Your double pumper should have came with the relay and hot wire kit. Regardless you need to mount the hobbs switch under the hood (unless you plan on running a super long vacuum line to the trunk). Why not just mount the relay, hobbs switch, and all related wiring under the hood, then just run your hot (power) wire to the second pump like normal? I dont see any advantage of mounting anything in the trucnk.

Plus, my double pumper has two wires coming out of the relay for an indicator light (which I REALLY like so that I know the pump is being told to turn on). I have it hooked up to the "car is leveling" light on my dash. It turns on right when my wheelie starts

 

[BadAssGN]

It's really easy to run two wires to the relay which you should mount in the trunk to keep the engine bay less cluttered.

wire the "hot line" to the alternator, then to a fuse right at the alternator, then to the power side of the relay, then for the hobbs switch I always use the ground side to switch the relay, rather than running yet another power wire though your car. so from a good ground to the hobbs switch, from the hobbs switch to the relay ground on the control side.
for the control power of the relay you can simply run a small jumper to the control power from the main hotwire comming back

so to recap. using the diagram below.

#87 will be the power to the Fuelpump
#86 will have a small jumper to #30
#30 is the hot line from the Alternator
#85 will be the ground Signal from the Hobbs switch.

I run most relays with ground side switching, less chance of an electrical short to ground.

 

[bison]

It's really easy to run two wires to the relay which you should mount in the trunk to keep the engine bay less cluttered.

wire the "hot line" to the alternator, then to a fuse right at the alternator, then to the power side of the relay, then for the hobbs switch I always use the ground side to switch the relay, rather than running yet another power wire though your car. so from a good ground to the hobbs switch, from the hobbs switch to the relay ground on the control side.
for the control power of the relay you can simply run a small jumper to the control power from the main hotwire comming back

so to recap. using the diagram below.

#87 will be the power to the Fuelpump
#86 will have a small jumper to #30
#30 is the hot line from the Alternator
#85 will be the ground Signal from the Hobbs switch.

I run most relays with ground side switching, less chance of an electrical short to ground.

Do this and you will be good to go. Use any 4 prong 30 amp auto relay. Radio shack has them cheap.

 

[BadAssGN]

I might also add if you want a indicator light just use the signal ground from the hobbs switch to activate light in your dash. wire the positive to ign power and your good to go.

 

[KevinB]

I might also add if you want a indicator light just use the signal ground from the hobbs switch to activate light in your dash. wire the positive to ign power and your good to go.

I think hooking the light up after the relay would be best. Then you know that the power is going to the pump and there is no problem with the relay or fuses.

 

[Fenrir]

Thanks for the input guys!