Installing A Defi Fuel Pressure Gauge: A Step-By-Step Guide

Defi is a private label manufactured by Nippon Seiki, the world's largest OEM and aftermarket gauge manufacturer. The company's performance auto parts include the Defi Advance BF Boost Gauge, oil pressure sensor products, and fuel pressure gauges. The installation process for Defi fuel pressure gauges involves mechanical and electrical components. While some users have reported a smooth installation process, others have encountered challenges with wire routing and securing connectors. It is important to carefully plan the wire routing to avoid exposure to water and outside elements. The sensors for Defi fuel pressure gauges have a 1/8 PT thread, and additional parts such as hoses, three-way joints, and sensor wires may be required for the installation.

Purchase the correct parts for your vehicle

When purchasing parts for your vehicle, it is important to confirm what commercial parts are needed for the installation. Defi sensors have a thread size of 1/8PT and a 7mm diameter at the end of the temperature sensor. The sensors for oil pressure and fuel pressure are common, and the pressure sensor wire is included in the package. However, a sensor attachment that is commercially available is necessary for the installation.

The sensor attachment for the oil pressure sensor can be either a 1/8PT adapter or a 1/8PT sensor attachment, along with sealing tape. For the fuel pressure sensor, the following parts are needed:

• 1/8PT three-way joint
• 1/8PT hose union
• Hose band
• Sealing tape

The sensors for oil temperature and water temperature are also common. The temperature sensor wire is included in the package, but a commercially available sensor attachment is required for installation. The sensor attachment for both oil and water temperature sensors is 1/8PT, along with sealing tape.

Additionally, the exhaust temperature sensor requires the following:

• Exhaust temperature sensor wire (included in the package)
• Sensor attachment (commercially available)
• Fitting (included in the product package for ADVANCE, Racer Gauge, and Defi-Link series)

It is important to note that the sensor wire differs between the Defi-Link series and other series. The sensor extension wire is common across all series.

Prepare the electrical harness

To prepare the electrical harness, you will need to power the gauges. You can do this by assembling the electrical harness before starting the installation. Here are the steps:

First, use some fuse taps to power the gauges. You will need to splice the red wire from the fuse tap to connect the same wire from both gauges, as they will be receiving the same power.

Next, use a 1/4" ring lug for the ground. Then, use 5A fuses to bridge the fuse tap connections for all three gauges. Technically, you should use a 1A fuse for the power source and illumination, as each one has a .3A inline fuse. However, by putting the wire from both gauges together, you can use a .6A or 1A fuse to protect the inline fuse.

Finally, connect the wires from both gauges together using a jumper to close the connection.

Install the sensors

To install the sensors for your Defi fuel pressure gauge, you will need to purchase the following parts separately:

• 1/8PT three-way joint
• 1/8PT hose union
• Hose band
• Sealing tape

First, prepare your sensors and put them into a Greddy Sandwich filter. Teflon-tape the sensor threads and tighten the sensors onto the sandwich block using a wrench until they are hand-tight.

Next, route the sensor wires underneath the firewall grommet and pass them through the side fender. Secure the wires to a chassis subframe piece closer to the oil pan, or near the headers.

Note: The location of the connectors may expose them to water, so ensure that they are waterproof.

Route the sensor wires

To route the sensor wires for your Defi fuel pressure gauge, begin by preparing the wires for connection to the sensors. The sensor wires should be included in the package of your product. Ensure you have the correct wires for your specific Defi model, as the sensor wire for the Defi-Link series differs from the other series.

Once you have identified the correct wires, you can proceed to route them to the sensors. The sensors should be installed using a commercially available sensor attachment, such as a Greddy Sandwich filter or an adapter plate. Teflon tape can be used to seal the sensor threads before tightening them onto the sensor attachment.

Now, you can route the sensor wires to the engine bay. One option is to route the wires underneath the firewall grommet, passing them through the side fender. If the wire length is insufficient, consider purchasing a sensor extension wire. Alternatively, you can secure the wires to a chassis subframe piece closer to the oil pan, taking into account the proximity to the headers and potential heat exposure.

When routing the wires, ensure they are protected and secured using methods such as wire looms, harness clips, and tie strap blocks. This will help prevent damage and ensure the wires are safely routed through the engine bay.

Finally, connect the sensor wires to the corresponding sensors, following any specific instructions provided by the manufacturer for your particular Defi model.

Connect the wires to the gauges

To connect the wires to your Defi fuel pressure gauge, you will need to purchase a few parts separately, as they are not included with the gauge. These parts include:

• A pressure sensor with a thread size of 1/8PT. This is a common sensor for both oil and fuel pressure.
• A fuel pressure sensor wire. The length of the wire will depend on your vehicle and the location of the gauge. Defi offers wires in 2.5m and 3m lengths.
• A sensor attachment, which is necessary to install the sensor.
• Other parts such as a three-way joint, hose union, hose band, and sealing tape.

Once you have gathered all the necessary parts, follow these steps to connect the wires to your gauges:

• Connect the fuel pressure sensor wire to the pressure sensor. The sensor wire should be included in the package of the product.
• Mount the pressure sensor to your vehicle's fuel system. The specific steps will depend on your vehicle's make and model. You may need to refer to your vehicle's repair manual or seek the assistance of a mechanic.
• Route the sensor wire through your vehicle, ensuring it is securely fastened and does not interfere with any moving parts. The exact routing will depend on your vehicle's layout.
• Connect the sensor wire to the gauge. The gauge should have a port or connector specifically for the sensor wire. Ensure that the connection is secure and that the wire is not damaged or frayed.
• Connect the power and ground wires to the gauge. The power wire should be connected to a 12V power source, such as the vehicle's fuse box or battery. The ground wire should be connected to a clean metal surface on the vehicle's chassis.
• Test the gauge to ensure it is working properly. Turn on the vehicle's ignition and observe the gauge to ensure it is displaying the correct fuel pressure readings.

It is important to note that the specific steps may vary depending on your vehicle's make and model, as well as the specific Defi fuel pressure gauge you are installing. Always refer to the installation instructions provided by Defi or a certified mechanic for the most accurate and up-to-date information.

Frequently asked questions