How to add a relay to a Walbro pump
 

My head is spinning trying to understand the technical side of adding a relay. I read the threads but still not clear. Can someone break it down on the procedure? Also whats the reason for the relay.

Thanks in advance!

Relay allows you to use a low current wire to switch a high current circuit on and off... so it effectively allows you to use a small OEM wire as a trigger to turn on a new larger wire system to the fuel pump. You can wire big wire to the pump to allow for more current draw and don't have to rewire the stock crappy small wire 😀

Thanks for the explanation! So I understand correctly, I wire the pump with 10ga and from the factory plug I connect a relay and from the relay on I can use the factory wiring? Or continue with 10ga to the battery terminal?

So technically both. For information on how a relay works see https://www.swe-check.com.au/editori...ing_relays.php

You are connecting both a ground and a strong 12V connection to the relay (normally from battery) , and using the old signal wire from the factory wiring to tell the relay to activate and give the full 12v from the battery directly to the fuel pump as needed. So you would generally connect ground to pin 85, connect the battery to pin 30 (please use a in-line fuse for protection, use a 30amp if you are running the walbro 450, but look up fuel pump and recommended fuse size) connect the old factory wiring positive to pin 86, and connect the fuel pump to pin 87. If your relay comes with 5 pins, you should cover the 87a with electrical tape, as that is on whenever pin 87 is off and vice versa.

What the relay is doing is when it detects the signal from the factory harness on pin 86, it activates a coil which flips a switch inside the relay (whenever you hear clicking in a car most likely it is from one of these relays) and allows 12v to flow from the battery to your fuel pump un-interrupted and without power loss due to connections, old wiring, small wiring, etc. This is beneficial, as normally the fuel pump power flows through a lot of unnecessary steps. The only drawback to running the fuel pump directly from the battery is that you lose the low/high voltage system that comes stock, and you may notice more fuel pump noise than you are normally used to. In my experience, using a genuine walbro 450 with IRP's pump mount that has rubber isolators has not significantly increased fuel pump noise in the cabin.

Thank you wazway. A very informative write up. Can you just point me in the right direction as to where to find the schematics fit the pin locations you mention? Thanks

Thank you wazway. A very informative write up. Can you just point me in the right direction as to where to find the schematics fit the pin locations you mention? Thanks

Post 10 has a diagram

https://www.rx7club.com/3rd-generati...l-pump-847009/

Has anyone done a dual pump setup, with two relays? I have a CJ dual pump setup but only have one pump for now, I have the second pump but not sure how to do the wiring portion to make sure both pumps get good 12v

Two relays. For the secondary pump relay you can trigger it the same as the first relay, you can use a Hobbs switch so it only comes on under boost, or you can trigger it with your aftermarket ECU is you have one. Both relays should have their own direct 12v source from the battery.

The issue is as these cars age with wiring deteriorates and you get voltage drop at the pump. Any upgraded fuel pump really should have a dedicated relay to ensure consistent voltage. Here's a simple drawing explaining how it is wired. We sell a complete kit with relay, pump and bracket to make installation trouble free. https://www.irperformance.com/produc...-pump-adapter/

https://cimg7.ibsrv.net/gimg/www.rx7...95f0484974.jpg

Can anyone recommend a general plug connector to put the wires coming out of the fuel pump hanger to the factory harness? I plan to cut off the factory connector and use a universal male and female connector. Reason being is that I removed the factory connector on the oem fuel pump hanger and installed a bulkhead connector with thicker wires.
Thanks