Radium DIY Fuel Pump Wiring and Relay Kit, 40A, One Pump

Radium Engineering DIY Fuel Pump Wiring and Relay Kit, 40A - Part #17-0031

A 450 lph pump or a Bosch 044 pulls 15 to 20 amps at full pressure, and the factory Honda pump circuit was never sized for that. Running a big pump on the stock wiring gives you a pump that's slow, hot, and starved at the top of the rev range where you need it. Radium's 17-0031 is everything to wire one pump properly, with a sealed 40 amp relay, a sealed fuse holder, 10 gauge wire, and the connectors, in a single kit with a wiring diagram.

What It Is and Why It Works

The kit builds a dedicated power circuit for one pump: battery to a 20 amp mini fuse, fuse to a 12 volt 40 amp SPDT relay, relay to the pump on 10 AWG, with the factory pump signal used only to trigger the relay. The relay and fuse holder are weatherproof with mounting tabs, so they can live in a trunk or under the car near a surge tank. The wire is 10 AWG TXL, the thin-wall aircraft-grade insulation that shrugs off fuel and heat and takes up half the space of GPT wire. Connections are Raychem solder-sleeve butt splices that shrink and solder in one step, plus a Posi-Tap for the trigger, four 6mm ring terminals and one 5mm, which is what you need to land on a Bosch 044 or a bulkhead stud. Radium's rule, and ours: one fuse and one relay per pump. A dual-pump surge tank needs two of these kits.

Specs

Fitment

Not vehicle-specific. Order one kit per pump; Radium recommends a dedicated fuse and relay for each pump on a multi-pump surge tank.

What to Know Before You Buy

Land the relay's power lead on the battery or a fused distribution stud, not on an accessory circuit, and keep the run short; 10 feet of 10 AWG is plenty for a trunk-mounted surge tank on a Civic. The trigger can be a switched 12 volt or a ground, as long as the other side of the relay coil goes to the opposite; the factory pump feed is the usual trigger, tapped with the Posi-Tap. Ten gauge is right for a 450 or an 044; if you're running a brushless pump that pulls more than 20 amps, you need a bigger fuse and wire than this kit. Route the 10 AWG away from the exhaust and through grommets, and put the fuse as close to the battery as you can.