How to Direct Wire a Fuel Pump (2-Part Guide)

Fuel pumps are important components in motor vehicles, as they supply liquid fuel to the carburetor (also called fuel injector) in internal combustion engines.

But if a fuel pump is not wired or installed correctly, it may not transfer fuel to the carburetor, and if the engine doesn’t receive adequate fuel, it won’t work properly. Also, the wiring technique depends on the wire’s length, thickness, and current the fuel pump draws.

Quick Answer: To wire a fuel pump directly, make proper connections by putting the fuse close to the battery:

  • Locate pin 30 on the relay circuit and connect it directly to the battery.
  • Locate pin 87 from the relay and terminate it on the battery’s positive terminal.
  • Connect Pin 85 (the ground wire) to the fuel pump’s negative terminal.
  • The white trigger wire on Pin 86 causes the relay to click and turn on the fuel pump. You can hook up a toggle switch to trigger the fuel pump. Use a heavy-duty wire when upgrading the fuel pump system to a higher volume one. Run it from the battery via the fuse to Pin 30 on the relay system and another heavy-duty wire from the relay to the fuel pump.

In this guide, I will provide detailed instructions to guide you through 2 parts to wire a fuel pump directly.


I will now show you how to connect your fuel pump system to the relay and trigger and, finally, how to wire the fuel pump in 2 parts directly:

  • In Part 1, we will disconnect and, if necessary, remove the existing fuel pump.
  • In Part 2, we will wire the fuel pump directly.

Locating the fuel pressure regulator while wiring a fuel pump is crucial. I will show you how to wire your car’s fuel pump directly in less than an hour. This wiring process is known as the “Fuel Pump Relay Bypass.” You may also want to use a heavy gauge wire instead of the existing one to boost fuel pump performance and the volume of fuel transferred to the engine.

Part 1: Removing the Fuel Pump

Step 1: Remove Components

Step 1 is necessary, whereas steps 2-5 are optional if you want to upgrade the fuel pump during this opportunity.

Remove the following components:

  • Take out the fuel pump after disconnecting the wiring. Also, disconnect the pipe to avoid kinks and snaps on the hard lines. You will need a 19 mm and 14 mm wrench for the lines. Ensure you use the correct wrench. Do not use vice grips, as you could face problems.
  • Remove the balmy – 800 mm heads. You may need to loosen these studs carefully, as they are notorious for snapping easily.
  • Disconnect the fuel pump wiring harness and lift it out cautiously. You may want to replace the fuel pump with a newer or a larger one to enhance the fuel pump’s volume. If that is the case, you should eliminate the current fuel pump.

To optionally remove the present fuel pump for upgrading, remove the fuel pump hanger by unscrewing the screws. Then, unplug the fuel pump equipped with a harness. Pull the fuel pump nozzle from the causing unit and remove the pump.

To remove the previous factory-installed fuel pump harness/wiring, proceed as follows:

Step 2: Locate the Stovepipe

Locate the causing unit stovepipe by opening the positive (red) wire on the stovepipe.

Step 3: Remove the Screws

Remove the screw that holds the bottom wire on the sending unit.

The bottom wire (from the pump) connects to the causing unit via a screw. Strip the bottom wire leaving the screw.

Step 4: Drill a Hole

Now, drill a hole for the replacement procedure. Then, install another wire with a hoop terminal.

Step 5: Remove the Rubber Fastening Factor

Pop off the rubber fastening factor using a flathead screwdriver to prepare for a fuel pump modification.

  • You may install a brass bolt via the hole and then employ a brass nut and washer under the hat to attach the fuel pump relay. Connect a wire with a hoop terminal on the topmost part of the bolt’s head.
  • Run a wire from the fuel pump via the hole or opening to the relay unit.

A person is holding a fuel pump without its wire
Video | ChrisFix

Part 2: Direct Wiring of the Fuel Pump

We will now start wiring the fuel pump.

You may bolt the bottom wire inside the sending unit. While installing a new pump, run a direct wire to the relay unit from the pump. Alternatively, you may cut the fat finish on the sending unit tube and then use a rubber pipage hose to connect the pump to the sending unit.

You can wire a fuel pump within the wiring harness and outside the fuel tank.

There is no complex or major modification to make in this part. It means it will only take a few minutes to complete the wiring. This is the best method, as the fuel pump or causation unit will not be altered.

Let’s move on to wire the fuel pump directly.

In this part, to direct wire a fuel pump cut the hot signal wire of the manufactured fuel pump. It is usually the black wire with white stripes for 1G AWD, which plugs into the fuel pump unit. Removing the fuel pump without cutting the hot signal wire is impossible. The hot signal wire connects to Pin 86 on the relay unit.

The following procedure will help you set up the circuit, where the relay and fuel pump are the key components:

Step 1: Connect the Pins

Connect the pins as follows:

  • Pin 30: Connect Pin 30 on the relay unit to the 12V battery with a wire.
  • Pin 85: This pin goes straight to the ground. Run a wire from this pin to the ground. Note its color to avoid confusion – use different colors for different pins.
  • Pin 86: This is the hot signal wire.
  • Pin 87: You might have extra wires on your fuel pump due to a lack of a connector. In that case, consider running a wire from the fuel pump’s recent aspect to Pin 87.

Here’s a tabular summary of the pin connections:

Relay PinConnection
85Ground connection
86Hot signal or trigger wire
87To fuel pump
30To relay unit with 12V battery

Step 2: Run a Fuse

I recommend that you run a fuse within the battery feed connections.

See the wiring diagram below to learn how to connect the fuse to the fuel pump circuit.

A fuel pump safety switch wiring diagram

Frequently Asked Questions

Should I hardwire my fuel pump?

Yes, you can hardwire your fuel pump if it is not getting enough current. You may also wonder if the FP flow varies while running or maintains constant pressure. Well, it is the manifold vacuum that regulates fuel pressure.

What is the color of the power wire?

The color depends on the car or vehicle model. However, most manufacturers prefer red and black, while others may use grey, orange, or purple.

What will happen if I wire my fuel pump backward?

Backward wiring will destroy the fuel pump. The fuel pumps chill themselves with the fuel. If they do not receive the fuel, they will die out faster.

Do electrical fuel pumps require a relay system?

fuel pump and a relay system wires and tools

Well, that will depend on the following factors:

  • The length of the wire
  • The thickness of the wire
  • The amount of current the pump pulls in
  • The various types of control on the fuel pump circuit

Your fuel pump system can function normally without a relay unit if there are low-current pumps and short circuits.

What gauge wire do I need to use for my fuel pump?

Use 15-inch of 12-gauge wires for your fuel pump. Get 5-inch 12-gauge wires for the relay power unit and 5-inch 14-gauge wires for the ground and trigger. Incorporate mounting hardware and terminals.

What is preventing my fuel pump from getting power?

If your pump or the relay is not getting power, your circuit may have electrical problems in your vehicle.

There could also be a problem with your switch or the circuit. Discontinuity in the wiring harness alters the current flow to the circuit components – relay, fuel pump, etc.

Check the continuity of your wires with a multimeter. Also, try to identify connection problems and rectify them.


Website Resources:

Video References:

Ratty Muscle Car


Delphi Technologies

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About Sam Orlovsky

AvatarCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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