I was just doing some searching on fuel pump wiring and see quite a few recommend running a new relay for a constant 12v to the pump. My question is why do that when according to the schematic you can jump the factory fuel pump speed relay and then remove the resistor so you get a constant 12v out of the factory main fp relay? Seems much more simple to me, or am I missing something?

 

this should answer your question

https://www.rx7club.com/showthread.p...elay+fuel+pump

 

Yeah I did that also, I think I even replied in that thread. That just changes the source but doesn't bypass the speed relay I believe.

 

Now that I think about it you could even leave the speed relay alone and just jump the wires at the resistor.

 

Hey uncle can you post pics or draw up a diagrahm of what you are talking about? i was going to do this mod and im not sure what to do.

 

I can't right now cause I'm on my iPhone but all you need to do is unplug the fuel pump resistor, cut the plug off it and splice those two wires together. Now plug you newly spliced connector back in the harness and viola, no more stepped voltage to the pump. You don't even have to touch the speed relay, you just bypassed it. If your talking about just getting the source off the ign circuit just follow the link papsmagu posted.

 

You can remove the relay and use a jumper wire, but you are still running the circuit through the crappy Mazda wiring. I like to run 12v right to the pump.

 

I can understand that, thanks for the input Ihor.

 

You are just running newer, heavier gauge wire to the pump. And the only way to do that is to either replace all the factory fuel pump wiring (which is not really feasible) or use the stock wiring to trigger a relay that will pull current through new wires.

 

Fair enough. Is it common to experience excess heat, voltage drop or even wiring failure with a single pump and the stock body harness wiring?

 

what's common is getting less than 12 volts to the fuel pump on stock wiring under load, and the purpose of a fuel pump rewire is to correct that.

 

Yeah I understand that, but that can be fixed by removing the source from the ign with a jumper wire no?

 

I suppose you could do it that way, then test to see if the voltage goes to whatever your alternator puts out usually 13.6 - 14.1V. But If you run new wires direct from the battery you KNOW the wiring is the best it can be. The factory wiring is not the most direct and a bit on the light side for an aftermarket pump. Just adding a larger ground wire adds like half a volt.

Many people get by without doing any modification to the pump wiring, but if you want the most from your pump you do what it takes to get the most out of it. When I first rewired mine I did the rewire on top of the fuel pump lid at the fuel pump connector, this still left the small wires going down into the tank, when I added my second pump I took this time to run full 10G wires directly to the pumps. Not sure how much it helps replacing this 1 ft of light gauge wire, but at least I know they are receiving all that they can.

I also already had a 4 gauge wire run to the hatch area that I put a distribution block on so running direct to the pumps was practical.