Rail Fuel Pressure Sensor: Location, Test, Diagram, Working

The rail fuel pressure sensor is an important part of the fuel system for petrol and diesel engines. Two regulators can be installed in the car depending on the design of the fuel system, for the low-pressure and high-pressure lines.

The correctness of the regulator directly affects the quality of the engine, a faulty unit reduces the engine life of the internal combustion engine by 15%, and the life of the fuel pump by 50%.

Rail Fuel Pressure Sensor: Location, Test, Symptoms, Working

Rail fuel pressure sensor location, Principle of operation, and design

The fuel pressure regulator (hereinafter RTD) is mounted on the ramp, for diesel engines with fuel supply through the COMMON RAIL system, and gasoline ICEs, the location of the fuel pressure sensor is different. The only connection principle remains a pipe from a pump or mounting on a fuel rail. If the system involves fuel recirculation, which is typical for gasoline injection engines, the regulator is installed on the ramp. If the system does not involve dumping fuel from the rail, the sensor is mounted immediately after the fuel pump.

Structurally, the RTD consists of a metal membrane that flexes under fuel pressure and is tuned to a certain range of operations and an electrical control part. The electrical unit is represented by four strain gauges that change the resistance of the element in the process of mechanical action of the fuel on the membrane.

On some vehicles, there are two solid-state engines, on both high and low-pressure lines. Before checking the quality of the fuel mixture, both parts are diagnosed by measuring the output voltage. Based on the electrical impulse from the adjustment sensors, the ECU generates a signal to open/close the fuel valve.

Gasoline and diesel internal combustion engines have the same output voltage at fuel pressure sensor of about 1.3 V, but the parameters of the fuel pressure that enters the injectors differ.

Sensor output voltage, VDiesel pressure, BarGasoline pressure, Bar

fuel rail pressure sensor wiring diagram

fuel rail pressure sensor wiring diagram
fuel rail pressure sensor wiring diagram

Where can I buy fuel pressure sensor?

Spare parts and other products for the car are easily available for purchase in the auto shops of your city. But there is another method that has recently received significant improvements. It is no longer necessary to wait a long time for a parcel from China, Japan, etc it became possible to ship from transshipment warehouses located in various countries.

bad fuel pressure sensor symptoms

In all cars after 2000, RTDs are integrated into the engine control unit, and in case of any malfunction, “Check” will light up on the dashboard. There are old diesel engines that are equipped with mechanical regulators, the diagnostics of the elements are carried out according to plan or after a malfunction in the internal combustion engine. Typical symptoms of a faulty sensor:

  • In addition to the “Check Engine” signal, the following error codes are output: P0190-P0194.
  • A sharp decrease in ICE power, and loss of traction, are often detected during overtaking, the car does not have the power for dynamic acceleration even up to 120 km / h.
  • Fuel overrun.
  • The car does not start well, regardless of whether the engine is warmed up or not.
  • Diesel internal combustion engines are characterized by the appearance of dips at high speeds when the engine does not respond to speed reduction.

The main danger of moving with a broken sensor is that the pump starts to work in emergency mode, which leads to its rapid wear.

If, after scanning diagnostics, error P1181 is detected – depressurization of the fuel rail, first of all it is necessary to check the regulator, the error may indicate wear of the installation gasket.

The reasons for the failure of the regulator are in its design features. This is wear or rupture of the membrane or a violation of the electro contact group. Separately, there is a wiring malfunction. During sensor diagnostics, the condition of the connection terminals and the quality of the cable is checked. fuel pressure sensor is not repaired, the element is changed to a new one, selecting a regulator for a specific brand of car and type of fuel.

The average service life of the sensor is from 5 years. A characteristic feature of the part is that the malfunction does not occur in 1 day. Rupture and stretching of the membrane occur slowly, in 80% of cases, drivers note that with minimal wear of the regulator, there were practically no noticeable disturbances in the operation of the internal combustion engine. An exception is a break in the wires of the block.

After installing the sensor, it is necessary to register the element in the computer, more often this does not apply to the original spare part, but to the analog.

fuel pressure sensor test Methods and Ways

Depending on which fuel supply system is used for the car, there are three ways to test the sensor for operability without dismantling the fuel rail:

  • a mechanical method for an old-style car with rubber fuel dump hoses for gasoline ICEs;
  • multimeter;
  • pressure gauge.

Dismantling the rail and subsequent diagnostics of the regulator is a more reliable way to check the quality of the mixture, since all adjacent components and wiring are checked along with fuel pressure sensor. Diagnostics in most cases is carried out at the service station, since you will need to use a special stand. Self-diagnosis in the garage without dismantling the rail requires a tester and is carried out in 15 minutes.

fuel pressure sensor test Methods and Ways

Mechanical diagnostics of the old-style regulator

For gasoline internal combustion engines in the fuel extraction system of which a rubber pipe is used, the sensor is located at the pump inlet. The check is carried out only on a cold engine.

  • Start the engine.
  • Remember the nature of its work (a faulty sensor gives a trip to the motor).
  • Pinch the fuel outlet pipe for 1–3 seconds with pliers.

If the fault is in the regulator, the engine will restore its operation, the revolutions become smooth, and jerks disappear. If, after the outlet pipe is closed, the motor continues to work incorrectly, the malfunction may be in clogged filters, or worn contacts, while the sensor is working.

testing fuel pressure sensor with multimeter

With the help of a tester, the operability of the RTD and the quality of the power supply from the block are checked. Checking the electrical signal to the block is carried out in steps.

  • Remove the block from the sensor.
  • Set the multimeter to voltage measurement mode.
  • Set the tester’s black lead to “minus”, connect the red probe to the block connector.

If nothing interferes with the passage of electricity to the sensor, there is no voltage loss, the value of 5 V will be displayed on the tester screen. The tolerance is ±1%.

The second stage checks the quality of the output signal from the electrical part of the regulator. Checking the signal from the sensor in steps.

The black probe from the tester is connected to the negative terminal of the battery, the red probe is connected to the signal wire of the regulator (more often the wire is located in the block in the middle in a red braid).

Start the engine, let it run for 1 minute at minimum idle speed. In this speed mode, the output voltage at the fuel pressure sensor should remain at a minimum of 1.3 V.

With an increase in speed, the voltage parameter from the sensor should increase to 5 V. If the node is faulty, at the highest speed, the readings can differ significantly both up (in 10% of cases) and down. This leads to the fact that the pump starts to pump fuel and switches to emergency operation.

testing fuel pressure sensor with pressure gauge

To check the sensor for operability, use a pressure gauge, a device for measuring pressure in the rail and pipes of the fuel system, air pressure in tires, and so on. Before checking with a pressure gauge, it is necessary to disconnect the vacuum hose from the system and connect the device between the fitting and the fuel pipe.

Before diagnosing, it is necessary to clarify the pressure value for a particular vehicle according to the manual. The working pressure for gasoline engines ranges from 2.5–3 atm. In the process of regassing, the pressure drops by 1–2% of the norm, a serviceable valve keeps the value within the acceptable range.

Sensors for diesel systems COMMON RAIL type BOSCH

Bosch’s high-performance COMMON RAIL direct injection systems have gained great popularity due to their efficiency, reduced fuel consumption and reliability. There are three types of fuel supply systems, each of which is equipped with a high-pressure fuel pump of a certain class and level:

  • with a control valve on the high-pressure rail;
  • fuel adjustment on the high-pressure pipe at the exit to the high-pressure fuel pump;
  • type “double control”, with two RTDs on the high and low-pressure lines.

You can determine exactly where the regulator is located after studying the fuel supply system of a particular engine. Primary diagnostics is recommended to be carried out with a multimeter. Original Bosch sensors for COMMON RAIL have a service life of 10 years, they fail last, therefore, in case of any violations in the operation mode of a diesel engine, diagnostics begin with checking injectors, high-pressure fuel pumps, and diesel quality.


Here we have shown you what is Rail Fuel Pressure Sensor where is it located in engine and how to test this sensor. You can change the Rail Fuel Pressure Sensor yourself in 15 minutes in the garage, the procedure is quite simple. But in order to change the element, it is necessary to make sure that the incorrect operation of the internal combustion engine is associated with the failure of the regulator.

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