How to Bypass Fuel Pump Relay?

The fuel pump relay function helps you start your car. If you cannot replace or repair the relay of a fuel pump quickly, you may bypass it and continue driving your vehicle. The relay makes the fuel pump compel the fuel system while turning on the car ignition. However, bypassing the relay of a fuel pump could result in a high-pressure fuel pump.

How do You Jump a Fuel Pump Relay?

Bypassing the relay implies directing electricity from the relay straight to the fuel pump through an electrical conductor. The only thing needed to send current from a Power Control Module to a fuel pump is a metal conductor, and you will need it to successfully pass a current to your car Power Control Module (PCM).How do You Jump a Fuel Pump Relay


  • Before you start, make sure to park your vehicle on level ground.
  • Then, lift the car hood or bonnet and locate the relay hub. You can find it at the engine’s right-hand side chamber, behind the driver-side headlight.
  • The fuel pump relay can be located in a plastic container or box, usually black, containing all of the vehicle’s relays.
  • Use the illustrative drawing on the lid to find the relay.
  • Take away the four-pin relay of the fuel pump from the box.
  • Get a copper wire about six inches long and strip about half-inch off from both ends of the wire with a stripper.
  • You should insert one head of the stripped copper wire in the top left pin slots of the four-pinned socket, in which you plugged the relay of the fuel pump.
  • Plug another head of the copper wire directly into the low-right hand pinhole of the four-pinned socket, where you plugged the relay for the fuel pump in the relay hub.
  • Then start the cars and check to see whether it works.
  • The fuel pump definitely will power on if you adequately place the two heads of the copper wire.

Read Also: How To Bypass Fuel Pump Relay On Chevy Truck?

How Do You Straight Wire a Fuel Pump?

The crucial part of every car is the wiring in the fuel pump. The engine won’t run if you don’t do the wiring correctly.

Fundamental Components

The primary parts of an electric fuel pump are the negative and positive electrical connectors on your car pump itself, the relay switch of the pump, the fuel pump fuse, and the fuel supply units in your car’s fuse box. Electricity is hazardous, and therefore, endeavor to disconnect your car battery and the fuel pump’s fuse located in the fuse unit. Electricity is not something you treat lightly.

Any open-wire can cause a spark when fuel evaporation occurs, leading to a significant disaster. Be careful.

Electrical Connection

The pumps’ electrical connections are the first to wire a fuel pump. The pumps’ electrical connections are the first to wire a fuel pump. Be sure the fuel pump’s negative and positive wires labels. This primary task must be followed when working on an electrical part of your vehicle to avoid getting a shock, frying some car components, or causing a spark. If you skip this step in wiring, the pump and probably all the electrical system will be ruined the moment you start your car. Wrapping a piece of paper/masking tape on the – and + wire will be enough.

Physical Wiring

Connect the wires to the correct positions once you have disconnected the fuse from the box and the battery wire. Connect the positive wire of the fuel pump to the one from your car wiring harness. Ensure the connections are secure and tight. Ensure it does not touch any metal surface to avoid bridging the connection. Failure to do so can cause a poor voltage supply and wreck the pump.Physical Wiring a fuel pump relay

The next step is to attach the ground/earth wire of the fuel pump to the closest electrical ground/earth surface (your car frame will do). When connecting the ground/earth wire, keep the connecting heads of the wire and surface rust-free. Although stated before, you must double-check to see that you have a tight and solid connection. A connection with a loose end may build up the heat around the wire, disrupting the supply of power to the pump and may cause it to malfunction.

Bypassing a Fuel Pump Control

The Fuel Pump Control Module regulates the voltage supplied to a car’s fuel pump. The module ensures proper fuel pressure and fuel supply to the engine over its entire range of operation by regulating the voltage.How to Bypass Fuel Pump Relay

To bypass the pump control, locate the connector at the Fuel pump Controller module underneath the spare tire and supply the yellow/gray wire with power. Ground the brown/white wire, and then the pump will run.

Learn More: How to Bypass ASD Relay

What Does a Fuel Cut Off Relay Do?

The relay powers the pump when the engine is running and stops when the engine stops.

What does it do? It stops the fuel pump from supplying fuel in case of an accident.

In other words, the fuel pump runs while your car is running. The fuel pumps and stops once you turn on the key until the engine runs. If your vehicle is in motion with your carburetor bowl filled up, the fuel pump will stop until the float valve opens, and it runs again till the valve closes again.

How to Know a Bad Fuel Pump Relay

Most people don’t know that their car fuel pump relay is broken until their cars cannot start.

We recommend replacing this item as soon as possible to avoid damaging your fuel pump or a fuel line. It’s a low-cost part.

Pro-tip: P0231 is a technical code for Fuel Pump Auxiliary Circuits Low Voltage.

Here are essential methods for determining a damaged fuel pump relay:

The Cel Is Illuminating

The primary cause is a CEL in most situations. The Electronic Control Unit stores a fault code to indicate that the pressure of the fuel is failing, which will cause illumination in the check engine light. You will need a scan tool (OBD2) to interpret the code. A P0231 or P0230 OBD2 DTC indicates a problem with the fuel pump’s main circuit.

Furthermore, a faulty fuel pump relay may cause a power spike in a fuel pump relay. This spike is usually a result of a bad fuel pump, a blown fuse, a damaged circuit, or frayed wire. The Electronic Control Unit will depict the voltage readings as error code, causing the engine’s light to illuminate.

Irregular Acceleration

Due to inconsistent fuel injection caused by a faulty pump relay, the fuel pump’s pressure will be altered. That affects the quantity of fuel that pumps to the combustion compartment. As a result, acceleration may be affected.

Dead Engine

This is the most serious indication that the relay of a fuel pump is faulty. Due to a fuel shortage in the combustion chambers, an uncompleted circuit will prohibit the fuel pump from operating, causing the engine not to start.

High Fuel Consumption

High fuel injection into the engine due to the lack of fuel pressure control may consume more.

How to Test the Fuel Pump Relay

In a case where the relay of a fuel pump is bad or about to fail, below are steps to test it.

  • Park your vehicle on a level and safe ground
  • Turn on the ignition but don’t start the vehicle
  • Raise your bonnet and find the relay
  • Turn the key to the on position
  • Remove your car battery’s negative wire
  • Use a nose plyer to remove the relay
  • Get and set your multimeter to the resistance mode (W)
  • Transmit energy to the voltage input pin
  • Replace the relay if damaged

In Conclusion

Reading this article, you now know how to jump a fuel pump relay, straight wire a fuel pump, bypass a fuel pump control, and what a cut-off relay does.

However, inspecting, detecting, and testing the fuel pump relay and associated circuits is preferable before throwing out a bad fuel pump. The problems will differ from car to car, and you might also receive plenty of issue codes in addition to the P0420 code. Remember that replacing a faulty relay is easier and less expensive than removing the fuel pump.