How the circuit works
On an Elite harness the fuel pump control wire is Orange/Blue. That wire doesn't carry pump current. It drives the coil of the fuel pump relay. When the ECU wants the pump running, it activates that output, the relay closes, and battery 12V flows through the relay contacts to the pump. That keeps the heavy current well away from the ECU.
Use a relay and fuse rated for your pump's current draw, like the 30A 5-pin power relay, mounted in a waterproof fuse and relay box. Keep the power and ground wires to the pump heavy and short, because voltage lost in the wiring means lost pump flow.
Get the pump right
- Size it for full power. The pump has to hold the right fuel pressure at maximum output, not just at idle. Run out of pump and the engine goes lean exactly when it can least afford to. As a rough guide from Haltech, a 500 hp gasoline engine needs around 210 lb/hr of fuel.
- Mount it low. The pump should sit below the outlet of the tank or surge tank so fuel feeds into it by gravity.
- Keep the fuel cool. Hot fuel is less dense, so the same injector pulse delivers less fuel by mass and the air/fuel ratio shifts. Route lines away from exhaust heat.
Need the fuel pump wiring diagram? Ask us and we'll send it over with advice for your build. For the rest of the loom, see the fuse block assembly and the wire color legend.
