How To Bypass A Fuel Rail Pressure Sensor?

Often common, it is to experience a check engine light triggered by a malfunction Fuel Rail Pressure. A useful skill to learn is how to temporarily bypass the sensor, at least to get you out of this difficult situation. One way which will be examined in this article is a test LED Light.

LED Light can create enough resistance once connected to the sensor connector. Once this happens, the Engine Control Unit (ECU) is tricked into believing that the sensor is still there.

We don’t recommend bypassing the Fuel Rail sensor without a proper alternative. A missing fuel rail pressure sensor could cause the engine to misfire, lower the engine power output and increase the fuel.

An alternative to the LED test light is a resistor, which will be introduced within the circuit. The resistor will also work like the test LED lights creating a resistance that will trick the ECU.

fuel rail pressure sensor symptoms

What is a fuel rail pressure sensor, and how it works?

The Fuel sensor rail pressure is a part of the fuel injection system. It monitors the fuel flow pressure through the rail. It is also a part of the fuel injection system that distributes fuel to the injector.

Furthermore, fuel rail pressure sensor location can be seen on the gas rail, while the fuel rail can be found along the injectors and the intake manifold.

Accurate fuel pressure is important to have an efficient working engine. The right fuel pressure allows the fuel injectors to atomize fuel so that the engine can produce more power while maintaining a good fuel economy.

The vehicle injection system and the ECU ensure the right fuel pressure is delivered to the injector. The rail pressure sensor is a major component the ECU uses to provide the right pressure to the injector.

How does a fuel rail pressure sensor work? The fuel rail is a high-pressure tube that collects fuel from the fuel pump and then delivers it to the injector. In the fuel rail lies a sensor, which collects data on the current pressure of the fuel flowing through the fuel rail.

Once the sensor can collect this data, it is immediately sent to the ECU, which is processed. The ECU then uses the data to monitor and regulate the fuel pressure according to what the engine requires.

Also, the ECU can adjust the fuel pressure using the high-pressure pump. The fuel pump can adjust the fuel pressure by sending signals to the fuel pump relay.

Read Also: How to Bypass ASD Relay

How do you diagnose a bad fuel rail pressure sensor?

There are several ways to properly diagnose a faulty fuel rail pressure sensor. You could diagnose the bad sensor by observing the signs that your vehicle is showing. There are some signs that your car could be exhibiting that are peculiar to the failed rail sensor.

Also, you could test the sensor using a multimeter for continuity or an OBD-II scan tool to check for fuel rail pressure sensor code. Observing the vehicle’s signs before testing the sensor would be better.

Below are some of the fuel rail pressure sensor signs.

Difficult to start

Fuel is an important aspect of the ignition process; the ECU ensures that an accurate amount of fuel pressure is sent to the ignition during the ignition process. However, when the fuel rail sensor is bad, the engine will not get the right fuel.

The wrong signal will be sent to the ECU, making the ECU send signals to the pump to deliver the wrong amount of fuel pressure. If the fuel pressure is too little, the engine will not start.

In addition, the engine may need to be cranked a couple of times before the engine starts.

Check the engine light.

An illuminated check engine light is one of the first signs you may experience when the sensor goes bad. The engine light shows that something is affecting the normal working condition of the engine.

If the rail pressure sensor is bad, the engine’s working condition is likely already affected. The engine will receive a different amount of fuel, making the engine underperform.

Reduce engine power

If a driver steps on the acceleration pedal, more fuel pressure is needed to meet the required acceleration. If the fuel rail pressure sensor is bad, it will not record the requirement leaving the ECU acting blindly.

The wrong fuel pressure will be sent to the engine; in most cases, the fuel is insufficient. When the ECU does not send the right amount of fuel and an optimal fuel-air mixture is not achieved, the engine power will drop suddenly. 

Engine misfiring

When the sensor is damaged, the engine will run lean or rich. If the engine runs lean, more air than fuel goes to the combustion system. On the other hand, if the engine runs rich, there is more fuel than air in the mixture. Both issues will lead to inefficient combustion of fuel, which causes the engine to misfire and run rough.

Reduced fuel economy

The ECU can force the engine to run rich due to false information or no information the engine gives. When the engine runs rich, more fuel is released to the combustion system, increasing fuel consumption.

If your vehicle exhibits two or more signs, your rail pressure sensor is likely bad. However, it is not a guarantee. Once you notice these signs, the next step is testing the sensor.

The fuel rail pressure sensor test we will be looking at is with a multimeter. Below is how to test the fuel rail pressure sensor with a multimeter.

  • Find the sensors that can be seen on the fuel injector rail.
  • Disconnect the connector of the sensor.
  • Set the multimeter to ohms settings.
  • Place the probes on the sensor terminal and observe the multimeter reading for continuity. If there is no continuity, then the sensor is bad.

Once the sensor fails the fuel rail pressure sensor test, the next step is to change the sensor immediately.

fuel rail pressure sensor location

Read Also: How to Bypass Catalytic Converter Check Engine Light?

How to bypass a fuel rail pressure sensor?

Is it possible to bypass the fuel rail pressure sensor? The simple answer is yes! However, a form of resistance must be created in the exact position or connector of the bad sensor. By creating a resistance, the ECU can be tricked into not detecting the missing or fuel rail pressure sensor for a while.

If you are wondering, “Can resistance be created?” The answer is through LED lights. Remove the damaged fuel rail pressure from the connector and connect the LED test light to the sensor signal wire. It will immediately add resistance.

Once the LED test light is successfully connected, it should illuminate, which shows that resistance has been established.

Also, you can use a resistor within the circuit to bypass the fuel rail pressure sensor. All that needs to be done is that one end of the resistor should be connected to the ground wire and the other to the signal wire. Just like the test LED light, it will fool the ECU.

What happens if I unplug the fuel rail pressure sensor?

Do not unplug the rail pressure sensor; if you do, the pump will run at a set speed which could affect the engine’s condition.

The pressure sensor helps the ECU properly monitor the fuel pressure produced by the pump. When the fuel pressure is too high, the sensor picks up the reading and sends it to the ECU. It then processed the signal from the sensor and reduced the fuel pressure by sending a signal to the pump relay. A similar process will happen if the fuel pressure is too low. 

If the fuel rail pressure is damaged and is then unplugged, there is no way the ECU can regulate the fuel pressure. The pump will deliver a fixed amount of fuel to the injector, which could harm the engine. When this happens, the engine will perform poorly, the engine will consume more fuel, and there will be an increase in emissions.

What is the difference between a fuel pressure sensor and a fuel rail pressure sensor?

There is a difference between the fuel pressure and the fuel sensor rail. The fuel pressure sensor is also known as the fuel tank pressure sensor. It is a part of the fuel pump assembly and can be found attached to the fuel. The sensor reads the fuel system’s pressure and detects evaporative leaks.

On the other hand, the fuel rail pressure sensor is common with common rail diesel or direct injection fuel systems. It provides the ECU with readings of the fuel pressure in the fuel rail. The fuel rail pressure sensor can be found mounted on the rail near the injector.

The fuel pressure sensor is part of the Evaporative Emissions System (EVAP) majorly informs the ECU of evaporative leaks. At the same time, the FRPS is a part of the injection system dedicated to informing the ECU of the pressure of the fuel going to the engine.

How much does it cost to replace the fuel rail pressure sensor?

You would pay between $200 and $350 to replace the rail sensor, depending on factors like the sensor brand and model of the vehicle.

Furthermore, it will cost between $150 and $250 to buy the sensor and an extra $50 to $100 to buy other parts. Other parts could include the wires, sensor, and other damaged parts.

If the sensor is going to be fixed by an expert, then you need to budget an extra $100 to $200 as a labor fee.

Final Words

You must understand that bypassing the fuel rail sensor is not a permanent solution to the sensor problem. It should only be used when stuck in a difficult position. It should be able to take you to your destination or the closest mechanic. Bypassing the sensor also comes with its disadvantages. Common ones to mention are reducing fuel pump lifespan, increasing fuel consumption, etc. 

Akindayini Temiloluwa

I am passionate about everything automotive. Right from when I got my first toy car as a kid, I developed an interest in the inner workings of vehicles. As I grew up, my love for mechanical stuff became more substantial enough for me to pursue a career in it. My goal as an automotive content writer is to simplify the most challenging concepts for my readers, help them self-diagnose what may be wrong with their vehicles and offer real value for their time.

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