The fuel rail has an important job in a vehicle – it supplies the fuel to the fuel injectors. Your vehicle’s engine cylinders are supposed to receive the correct amount of fuel at the optimum pressure to function – and the fuel rail pressure sensor makes sure that is what happens. The job of the sensor is to calculate the pressure and transmit the necessary information to the ECU.
Afterward, the ECU decides on the right fuel supply measure. When the fuel rail pressure sensor malfunctions, it can interrupt the engine’s fuel flow and force it to collapse. We don’t have to elaborate on much of an unwanted situation that is.
Car sensors are susceptible to damage from constant exposure to heat, pollutants, and general wear and tear. Unfortunately, the fuel rail sensor is not the most durable of components as it damages rather easily.
In this article, we talk about the signs of a faulty fuel rail pressure sensor, its functions, location, and the replacement cost if needed.
What Is The Function Of A Fuel Pressure Sensor?
As mentioned earlier, the sensor keeps track of the fuel pressure in the fuel rail. When the sensor detects this data, it is sent to the engine control unit, or ECU. From there, the ECU analyzes the data and makes the needed changes to the quantity of fuel injected alongside the timing of the injection. This allows for better engine performance for all driving conditions.
The ECU also specified the right amount of fuel required by the engine. Contrary to what many drivers think, if more fuel is poured into the combustion chamber, the vehicle’s fuel economy drops. On top of that, the service life of emissions-related components decreases, and excessive carbon is expelled into the air.
As the majority of modern-day vehicles are made as eco-friendly as possible, this makes fuel rail pressure sensors vital elements of the engine which have to be functional at all times.
Composition Of A Fuel Pressure Sensor
A fuel rail pressure sensor comprises a sensitive element inside coupled with an integrated electronic circuit. The sensitive element received pressurized fuel through a channel inside the sensor body. Then, the pressure is converted into electrical voltage. Amplified by the circuit, the voltage is sent to the ECU through the electrical contacts.
The sensor is a resistive strain sensor. Its operation is based on the piezoresistive effect. What is that? A piezoresistive effect suggests that the electrical resistance of a conductor differs based on the longitudinal mechanical deformation. Many silicon-based semiconductor films exist inside the sensitive element.
In addition, the fuel rail pressure sensor is active. It has to be powered by a voltage source, ideally +5V. 3 pins are there on the electrical connector: supply voltage (AU), output voltage (UV), and ground.
The signal generated by the sensor, based on the fuel pressure, ranges between 0 to 70 mV. This is then converted into a voltage that ranges between 0.5 to 4.5 V by the electronic circuit.
A fuel rail pressure sensor’s measuring range lies between 0 to 1800 (2000) bar. The sensor’s measuring accuracy plays an important role in ensuring the injection system works properly. At average injection pressure, the difference between the measured pressure and the actual value should not exceed ± 2%.
Signals created by the fuel rail pressure sensor are parts of the closed injection control loop. When a driver presses down on the gas pedal, the ECU measures the amount of fuel required to get the needed engine torque.
Location Of The Fuel Rail Pressure Sensor
The fuel pressure sensor can be found at the fuel rail near the intake manifold. Alternatively, it can also be located on the fuel line, but this is most rare. Have a look under the intake manifold and we assure you that you will find the fuel rail, injectors, and fuel rail pressure sensor.
Faulty Fuel Rail Pressure Sensor Symptoms
When the fuel rail pressure sensor fails, the engine starts running in failure mode since it does not contain data regarding the rail pressure’s value. In this case, the pressure is handled by the ECU.
The fuel pressure sensor can be considered a weak link in the system. Owners complain about the flimsy situation of this component as it can give up under higher temperatures.
Many wonder if they have to replace the high-pressure rail alongside the sensor. No, you don’t. Only the sensor needs to be replaced and that is a 15-minutes job.
Difficulty Starting The Car
In event of a fuel rail sensor malfunction, incorrect information is sent to the ECU, which alters with the settings. As a result, the fuel supply is inadvertently interrupted, making it harder to start your vehicle.
Poor Engine Performance
The performance of your vehicle will take a severe hit when the fuel rail pressure sensor is defective. You will try to accelerate but due to a lack of fuel supply, the engine will not be able to deliver enough power and the acceleration will be poor.
Moreover, a faulty pressure sensor sends mixed signals to the ECU so the unit may increase the amount of fuel being injected into the engine. Ultimately, you lose more fuel and have to refill the tank more frequently.
Check Engine Light
Perhaps the first symptom you will observe, an illuminated check engine light is indicative of a problem within the vehicle that has to be addressed as soon as possible. The ECU triggers the light once it detects the bad fuel pressure sensor. As a general rule, make sure to drop by the mechanics if the light ever blinks on your vehicle’s dashboard.
If you own an OBD2 scanner you can read the trouble codes yourself.
Incorrect supply of fuel to the engine results in an unprecedented stall. Regardless of how hard or how many times you try, the engine refuses to start again. If this occurs frequently, the fuel pressure sensor may not be functioning correctly enough to send the right information to the ECU. Consequently, if the ECU cannot make necessary adjustments, your vehicle will start developing additional problems.
Poor Fuel Economy
One more symptom you will notice is a different fuel consumption than regular. The fuel consumption can either be higher or lower than the usual measurement – which may sound like a good thing at first but your engine will hate it in the long run.
How Often You Should Replace The Fuel Rail Pressure Sensor
In theory, you shouldn’t ever have to replace the fuel rail pressure sensor of your vehicle. More often than not, these parts are made to serve the lifetime of the car. But similar to all other parts of the vehicle, there may come a time when the fuel rail pressure sensor goes bad. Unfortunately, they tend to fail with little to no warning and force you to replace the entire component.
The good news, however, is that although these parts go bad suddenly, the symptoms of damage appear a while before. This is why it is important to know and understand what these signs are so you can recognize the damage in its early stages and have the vehicle checked.
Can You Drive With A Bad Fuel Rail Pressure Sensor?
Perhaps the worst part of driving around in a vehicle with a faulty fuel rail pressure sensor is that you may not even know that there is an issue under the hood. On the bright side, you are not putting yourself in mortal danger by continuing to drive a vehicle like that. Worst case scenario: your wallet will run dry because you will need more tank refills than ever.
However, as the problem exacerbates, you will find that your vehicle is not as cooperative as it was before. It will be significantly more difficult to try and start the car and keep it running while you are out on the road.
And as the pressure sensor inches closer to completely dying on you, that is when the biggest issue will spring up. It will be a challenge to keep the car running for more than 5-10 seconds at a time.
Once that point is reached, the vehicle should not be driven around anymore. Apart from the fact that driving and maintaining a vehicle with a bad fuel rail pressure sensor will cost you a lot of money, you also risk yourself (and many others) when you are behind the wheels. It is best to take the vehicle off the road immediately and consult with a mechanic.
So, the effects of a bad fuel pressure sensor come in layers. Just because you are not having any bad experiences yet does not mean you will not have them in the future.
Fuel Rail Pressure Sensor Replacement Cost
The average cost of fuel pressure sensor replacement ranges between $100 to $300. While the actual component will cost you no more than $50 to $150 depending on the make and model of the vehicle, the labor costs match the price of the part.
You can DIY the repair and save some money. Replacing the fuel rail pressure sensor is fairly straightforward on most models of vehicles. Keep in mind that you will work with fuel – it can ignite if you are not cautious. Be careful with all repairs.
In some car models, the fuel rail pressure sensor will have to be reprogrammed to remove the trouble codes.
How To Test A Fuel Pressure Sensor
To test the fuel rail pressure sensor, you first need a multimeter. Follow the given steps sequentially to achieve the most accurate results.
Step 1: Disconnect The Sensor
First things first, unplug the sensor from the vehicle to start the test. If you are still not sure where the sensor is located, the owner’s manual should have information on that so refer to it. All you have to do is pull the plug to detach it from the battery line.
Step 2: Connect The Multimeter
After the sensor has been unplugged, start the vehicle and fetch your multimeter. The tool’s probes must be connected correctly to the wires in order to start the test. Tip: the red probe has to be linked to the positive wire whereas the black probe to the negative.
Once connected, the multimeter should begin working immediately and start showing values on the screen. Refer to the manual to understand whether the test results are good or bad. This will give you information about the right voltage requirements.
Step 3: Analyze The Results
Now that you have somewhat of an idea about the voltage levels, have a look at the readings given by the multimeter. Are the values within range or different? Wrong values mean there is something stopping the sensor from understanding the correct pressure or the entire system is bad.
Step 4: Check The Wiring
During the comparison, the values may come out right but that does not guarantee that the pressure sensor is okay. Silver lining: it saves you the trouble of replacing the whole system. Now that you know the sensor works fine, the wiring has to be checked. This is a general issue almost all car owners struggle with so there is no need to get worked up over it.
Check out the wiring condition under the hood. Disconnect and reconnect all the wires related to the sensor to ensure that they are in their designated places. We strongly recommend using the test box that comes with the vehicle when testing out the wiring. Since the box is tailored for your vehicle’s model, it shall contain all the tools you will need.
If the problem persists, take that as a sign to drop in by the local technician or dealership.
Step 5: Take Precautions
Preventive measures are always better than cures. To avoid similar issues in the future, consider investing in a fuel injection maintenance kit. A multifunctional cleaning toolset will help you keep the sensors clean at all times. Furthermore, they keep the passages clear to prevent any abnormal build-up of pressure from within.
This is a crucial part of the process and should never be overlooked since dirty fuel filters and fuel lines are primary indicators of a bad fuel system. They exert excessive strain on your vehicle and put a dent in the engine’s longevity.
How Are Fuel Rail Pressure Sensors Replaced?
If you are sure that you have a bad fuel rail pressure sensor situation on your hands, it is important to replace the part at your earliest convenience. You will have to do it anyway so there is no point ignoring it. Most ASE-certified mechanics will be able to complete the job in a jiffy.
Before working on the fuel pressure sensor, the mechanic will pull codes from the computer of the vehicle to double-check if there is an actual problem with the problem. They will then follow a series of steps to effectively remove the old fuel pressure sensor and replace it with a new one. Here is the process from start to finish:
- The mechanic starts by disabling the fuel pump of the car along with relieving any residual pressure left behind in the fuel system
- Disconnect the battery from the vehicle
- Remove the vehicle’s back seat to find an access cover on the floor underneath. This leads to the fuel pump assembly. The mechanic may also need to remove the fuel tank from under a car to perform this.
- The wiring harness connectors are disconnected from a fuel pump assembly before the fuel lines are detached from it.
- The whole fuel pump assembly is removed from the car and the fuel rail pressure sensor is taken out of it.
- A new fuel rail pressure sensor is installed into the fuel pump assembly before everything is reassembled.
- Only the battery has to be reattached. The car is ready to be driven after the new fuel rail pressure sensor is tested and everything has been reassembled.
You may think that this process is super complicated but most mechanics should be able to finish the job in under an hour or two.
Can You Replace A Fuel Rail Pressure Sensor By Yourself?
The fuel pressure sensor is not the transmission or the camshaft of a vehicle; replacing it is not that difficult. But we should say that does not mean that anyone should take on this job.
If you are not well versed in the many ways of the automobile and cannot work with many small parts of the fuel pump assembly, it is best you leave it to the professionals. You can end up doing severe damage to your vehicle if you make a mistake while changing the faulty fuel rail pressure sensor.
How To Replace A Bad Fuel Pressure Sensor
Luckily for you, replacing a bad fuel pressure sensor is one of the easiest car management DIY jobs you will ever encounter.
You Will Need The Following Items:
- Park the vehicle in a well-lit but shaded area. Turn the engine off.
- Detach the vehicle’s battery. Simply disconnect the negative cable and that should disable the power.
- Use the jack to raise up the car and take off the wheels on the side where the fuel tank can be found. This is where the rogue wrench will be useful.
- After the wheels have been removed, you should be able to see 2 pins on the lower side of the wheelhouse. Use a screwdriver to stick to their heads before pulling them out. Make sure you do not lose them during the process.
- Using the ⅜, remove the plastic screws located on the inner wheelhouse and process to remove the house. Place the wheel cover trim on the side. By now, there should be a clear view of the fuel pressure sensor.
- To detach the pressure sensor, start by pulling out the electrical wire. Pry up the sensor to remove it.
- Compare the new sensor with the old one. Are they similar? Good. Now, insert the new sensor in place, making sure it sits properly in its slot. Now, reconnect the electrical line.
- Reinstall the wheelhouse plus all other parts that had been removed and you are done! You have successfully installed a new fuel rail pressure sensor.
Can You Sell A Car With A Poor Fuel Rail Pressure Sensor?
If your old car has a bad fuel rail pressure sensor but you cannot bother to invest to have it fixed, you may start asking yourself what to do with the vehicle. Maybe someone out there would want to buy the vehicle off your hands. Under normal circumstances, that is highly unlikely. But, there are many junk car buyers you can get in touch with and they will gladly take away your unwanted vehicle.
Symptoms of a Bad Fuel Rail Pressure Sensor
- A fuel rail pressure sensor monitors the fuel pressure within the fuel rail and transmits data to the engine control unit.
- The engine control unit uses this data to adjust the timing and quantity of fuel injections, which optimizes engine performance for current driving conditions and maximizes fuel economy.
- When the fuel rail pressure sensor goes bad, the engine control unit won’t be able to function correctly, resulting in a decrease in fuel economy and increased carbon emissions.
- The five most common signs of a bad fuel rail pressure sensor include a Check Engine Light, difficulty starting the engine, weak acceleration, engine stalling, and reduced fuel economy.
- These symptoms can indicate other issues, but a diagnostic scan tool can usually confirm a problem with the fuel rail pressure sensor.
- Fuel rail pressure sensors are typically found in diesel and some gasoline engines and are located near the middle of the fuel rail.
- The cost to replace a fuel rail pressure sensor varies depending on the make and model of the vehicle, but on average, expect to pay between $200 and $340 for the replacement.
- Large vehicles will generally notice a more significant reduction in fuel economy than smaller ones.
- A fuel rail pressure sensor should not be confused with a fuel tank pressure sensor, which is located inside or on top of the fuel tank.
- Since most modern vehicles are designed to be environmentally friendly, the fuel rail pressure sensor is a crucial component that must remain functional at all times.
The fuel rail pressure sensor is one of the more hidden yet important components of the vehicle. It is interconnected with multiple other parts of the engine that work together to ensure the smooth operation of your vehicle.
During your vehicle’s routine maintenance, keep an eye out for these symptoms and perform regular checks to prevent a bad case of poor fuel pressure sensor situation. Hope we have covered everything that you needed to know to replace your bad fuel rail pressure sensor.