This mod is intended to supply the maximum amount of voltage available to the fuel pump, and upgrade the wires when using a Supra pump which usually pulls right around 20 amps, by getting power directly from the battery, and not through the complicated stock wiring circuit normally handles less than 15 amps. This has not been proved to be a necessary mod, so don’t go starting rumors. The idea for this originally came from Bryan “NoShoes” Moore as mentioned by Ricky Benitez on the MR2 Messageboard in this thread http://www.board.mr2faq.com/showthread.php?s=&postid=1569253 , thanks to everyone who contributed there. This is for informational purposes only, and to document what I did to my car. Only attempt this if you are handy with wiring and electronics. I barely am 🙂 If something described here does not make sense, do not continue until you get it clarified. You could fry the wiring in your car, the Fuel Pump, or blow up your car!!! Be careful.
1 Consumables : 14 gauge wire (Autozone), 30 Amp DPDT Auto Relay (Radio Shack), and 30AMP Fuse Holder (Autozone). Required Tools : Solder/Solder Gun, electrical tape or shrink tube, wire cutters, metal coat hanger.
2 Here’s the relay diagram and wiring info. 86 at the top of this diagram is going to be the 12v source that turns the relay on. 85 at the bottom is going to be the ground for the 12v source, connect this to a bolt connected to the body of the car. 87 at the right is going to be 12v directly from the battery. 30/51 is going to connect to the 12v blue wire on the fuel pump in the cabin. The final connection will be from the fuel pump white wire directly to the negative terminal on the battery.
3 Get access to the fuel pump power connector under the ashtray. Info on how to do this is in the the Fuel Pump Swap article in the Service section of this website. The green protective sheath is the Fuel Pump side (white wire is the Fuel PUmp Ground, and the Blue Wire is Fuel Pump 12v).
4 Cut the fuel pump power connector off on both sides of the connector. The side with the black sheath is the normal fuel pump power supply, but we are going to cut it and use it to trigger the relay. Cut it off as well, and tape up the white wires, they are not needed. The Yellow and Red wires and connector in the background is for the Fuel Sender for your Fuel Gauge (we won’t be touching that at all).
5 Here they are all cut up and ready for further work.
6 We are going to run 2 14 gauge wires, and one 16 gauge from the battery area to the ashtray area. Look at the red and black wires here. I’ve drilled a hole in the firewall and inserted a rubber grommet to protect the wires, and I pushed the red and black wires through to the passenger footwell. You can cut a hole in the stock grommet to the right, and push your wires through. I also had to push another 16 gauge wire through, but forgot before these pics.
7 Here’s the passenger footwell area. You can see that grommet and two of the wires.