How to Wire a Fuel Pressure Gauge
A fuel pressure gauge is important for obtaining the best possible performance from your vehicle. It lets you see if the fuel is underpressured as it flows through the fuel line so you can make adjustments if necessary. The electric fuel pressure gauge sits in the dash, unlike a standard fuel pressure gauge. The wiring is simple, so you don’t need much mechanical knowledge to fit a fuel pressure gauge.
Step 1 - The Kit
An electric fuel pressure gauge consists of 3 parts. There’s the sending unit which fits on the fuel line. This sends information to the pressure unit. This is effectively the brain of the kit. In turn this sends signals to the gauge itself, where the driver can check the fuel pressure in the line.
Step 2 - Sending Unit
The first step is to fit the sending unit on the fuel line. The line will need to be cut for this. Follow the manufacturer’s instructions, always making sure to first disconnect the negative battery terminal. Vent the fuel system before you fit the sending unit.
Step 3 - Gauge
The gauge can be fitted almost anywhere on the dash; many people like to screw it so it’s sitting on top and can easily be read. A white and a black wire come off the gauge. The black wire has to be attached to a good ground, while the white wire should be wired to the dash lighting. This will allow the gauge to illuminate at night.
Step 4 - Pressure Unit
The pressure unit should be located in the passenger area of the car rather than in the engine. It can either be screwed in place or attached with double-sided tape (in this instance the surface where it will be attached should be thoroughly cleaned first).
Step 5 - Wiring the Sending Unit
There will be 4 wires coming from the sending unit, fitted together in sheathing. Feed these around the engine compartment and then through a hole in the firewall so they reach the pressure unit. On the side of the pressure unit there will be 12 terminals. Strip the sheathing and the tips of the wires. The red wire attaches to terminal 8, the black, or ground, wire to terminal 11, and the white signal wire to terminal 12. The remaining wire attaches to terminal 9; this is the wire shield.
Step 6 - Wiring the Gauge
Use a black wire from terminal 1 of the pressure unit to attach the unit to a good chassis ground. Terminal 2 needs a red wire that attaches to a 12 volt source. The terminal on the ignition switch is ideal for this.
You will now have 1 wire left, a sheath containing green, red, and brown wires. On one end there will be round attachments to fit over the screws at the back of the fuel pressure gauge. The green wire should attach on the left, red in the middle and brown on the right. Tighten down the nuts with a wrench.
To complete the installation of the fuel pressure gauge, attach the other ends of the wires to the pressure unit. The green wire attaches to terminal 4, red to terminal 5 and brown to terminal 6. Reattach the negative battery terminal and turn on the engine.