Fuel pressure sensor in the rail: where is it located, how to check

How to change the pressure sensor on a car's fuel rail

The fuel rail sensor, like any part of the fuel system, can malfunction, usually resulting in a rough running engine, ignition problems, or other instances where the check engine light comes on.
The ATC fuel rail pressure sensor is a part that can reduce evaporative emissions by delivering a specific amount of fuel to the engine to keep it running properly. A pressure sensor ensures that excess fuel does not remain in the conductive channel.

The sensor's job is to determine the pressure directly in the fuel rail, thereby determining the exact amount of fuel in the rail. When the sensor detects the presence of fuel, an electrical signal is sent to the fuel pump for further pumping. As soon as the fuel pressure reaches a certain point, the fuel pump receives a signal to stop working. When the pressure decreases, a request is made to renew the fuel supply.

When a pressure sensor malfunctions, it can be determined by some initial signs that will tell you that something is wrong. Usually there are difficulties with ignition: it takes longer than expected to start the starter. In addition, the engine begins to operate unevenly. Sometimes problems with the pressure sensor on the fuel rail even lead to the engine simply stalling during normal operation.

The following are the alarm codes (for machines with a computer system) that correspond to the pressure sensor: P0087, P0088, P0170, P0171, P0172, P0173, P0174, P0175, P0213, P0214, P0190, P0191, P0192, P0193, P0194.

Installation locations

The installation location of this element depends on the design features of the power system. In most cases, cars use fuel recirculation systems. Its peculiarity comes down to the fact that excess fuel, which has already arrived at the injectors, is drained back into the tank. In such a system, the regulator is installed on the fuel rail (where the fuel is located before entering the injectors).

But there are also systems in which recirculation is not structurally provided for, although they are rare. Since there is no discharge of part of the gasoline from the ramp, the pressure in the system is adjusted before the fuel enters the ramp. In such systems, this element is installed immediately behind the fuel pump. It can be embedded in the fuel line or located in the tank.

Where can I buy

Spare parts and other products for the car are easily available for purchase at auto stores in your city. But there is another method that has recently received significant improvements. You no longer need to wait a long time for a parcel from China: the AliExpress online store now offers the opportunity to ship from transshipment warehouses located in various countries. For example, when ordering, you can specify the “Delivery from the Russian Federation” option.

Follow the links and choose:

Design Features

The gasoline pressure regulator is one of the few elements of the system that is not controlled from an electronic unit. This unit is completely mechanical and its operation is based on pressure differences. Although in systems without recirculation, the sensor is triggered by the ECU. Since they do not occur often, we will not consider such nodes further.

It is worth noting that the RTD does not operate in strictly specified values, it adapts to the operating mode of the engine. That is, if necessary, it increases or decreases the pressure in the system to ensure optimal mixture formation.

Structurally, this element is very simple and consists of a housing on which fittings and leads are located for connection to the power system. Inside, this housing is divided by a membrane into two chambers - fuel and vacuum.

There are outlets suitable for the fuel cavity - one is used to supply fuel to the chamber, and the second leads to the line for draining gasoline into the tank (return). But the second channel is closed by a valve, which is connected to the membrane.

A spring is installed on the side of the vacuum cavity, which acts on the membrane, ensuring that the drain channel is closed by the valve. This chamber is connected to the intake manifold by means of a fitting via a tube.

Absorber and its system

Some Lada cars have a fuel system with an absorber. An absorber is an indispensable thing nowadays. It serves to reduce emissions of fuel vapors into the environment.

Absorber

The absorber is a flask filled with special carbon that evaporates fuel vapors and supplies them to the car's receiver. Installed in the vehicle's engine panel.

Absorber sensor

The absorber sensor controls the opening and closing of the air supply to the absorber to control vapors. Installed on the engine cover in engine versions with a volume of 1.6 liters, in engine versions with a volume of 1.5 liters it is installed directly on the absorber flask.

Separator

The separator in Lada cars is installed under the rear left wing near the shock absorber strut and serves to expand the fuel vapor formed in the tank due to temperature changes. Externally, the separator looks like a coolant expansion tank.

Tilting valve

This valve is installed next to the separator under the rear left fender of the car. The valve serves to prevent fuel from entering an overturned car during an accident. That is, when the valve is turned over, it shuts off the fuel system, protecting the car involved in an accident from fire.

Location in the vehicle structure

In modern cars, two layouts of the fuel pressure regulator are used. In systems with a return line, it is installed on the fuel rail, and in designs without a “return” - directly inside the fuel tank (in the pump). The diagram located on the fuel rail involves connecting the regulator to two lines of the system:

Layout of the fuel pressure regulator in the system

• inlet - the supply channel from the fuel tank to the power system;
• return exhaust – channel for draining excess fuel (pressure relief).

In such a system, when the regulator opens, excess fuel enters the return line and then into the fuel tank. This scheme has some disadvantages:

• complexity of the design and the need to install an additional pipeline;
• heating of excess fuel when it enters the ramp, which increases the vapors generated in the tank.

Each fuel regulator has its own factory settings and is suitable for a given car model. There are also universal designs for injection systems, which are equipped with pressure gauges and the ability to manually adjust. They are installed instead of the standard regulator exclusively in the fuel rail.

When the fuel pressure regulator is placed directly in the tank, the required amount of working fluid with a given compression level immediately enters the engine without the use of an additional line. In this case, the excess is also discharged directly into the tank, but it does not enter the engine compartment, which eliminates its heating.

In this case, a constant pressure difference is established relative to atmospheric pressure, and the amount of vacuum in the intake manifold is taken into account by changing the injection duration.

Purpose of the regulator

The sensor maintains the optimal pressure in the fuel rail, necessary for the correct operation of the injectors in different operating modes of the unit. The RTD determines the intensity of fuel supply and its quantity. Fuel enters the engine cylinders through the injectors.

Dosing accuracy and maintaining the required pressure is ensured by a membrane control valve, onto which springs press at one end and fuel at the other. There are two options for placing an element:

• The RTD is used in power systems with a check valve and is mounted on the fuel rail.
• In designs without “return”, the sensor is installed on the fuel tank.

In the first case, the fuel pump pumps fuel through the line from the tank. The resulting pressure affects the regulator. The device contains two chambers: fuel and spring, which are delimited by a membrane.

Fuel enters through the intake hole and presses on the jumper. On the other hand, it is pressed by a spring and the pressure force of the collector. If the fuel pressure is stronger than the spring compression, the sensor opens slightly and dumps excess fuel into the check valve.

When the regulator is located in the tank, additional installation of the pipeline is not required. Excess fuel does not go into the space under the hood and does not need to be returned to the fuel compartment. It also heats up less and evaporates less.

There is another way to regulate the pressure - using an electronic circuit that does not have a mechanical sensor. In this case, control is provided by an electric fuel pump. Electronic sensors record voltage readings and regulate the flow of fuel. This solution saves fuel and reduces its heating.

The role of the fuel regulator in the car system

At different engine operating modes, it is necessary to create the appropriate fuel pressure in the fuel system. To implement this task in practice, a special pressure regulator is used. It is used in injection engines, where the correct operation of the engine depends on the accuracy of the injection parameters.

When the governor is faulty, the engine runs unevenly, acceleration times are increased, and in some cases power can be significantly reduced. So, for example, if the amount of air coming from the manifold remains unchanged, and there is more fuel than necessary, the air-fuel mixture will not ignite or will not burn completely.

Even if in this mode the electronic control unit shortens the injector opening interval, it will not be possible to completely compensate for the excess fuel pressure. This will lead to interruptions in engine operation and an increase in the amount of unburned fuel in the exhaust, which can prematurely damage the catalytic converter or particulate filter.

RTD defects: spring

The main problem with the regulator is the weakening of the spring, which causes premature draining of fuel into the return line. This leads to starvation of the engine: it does not have enough fuel to operate at high speeds, when the accelerator pedal is pressed, or in transient modes. A faulty regulator spring causes low fuel pressure in the fuel rail, which leads to a decrease in engine power, problems with the ECU and unstable operation of the engine.

Design and principle of operation

Fuel pressure regulator in closed (a) and open (b) positions.
The fuel regulator consists of the following elements:

• Frame. It is made of metal and has a high tightness necessary to prevent fuel leakage and loss of pressure.
• Membrane (diaphragm). Reacts to excess pressure and opens the drain line.
• Check valve. Located at the entrance.
• Spring. Places additional pressure on the valve diaphragm.
• Fittings for fastening fuel inlet and drain lines.
• Seals. Ensure the tightness of the system at the inlet and outlet.

Sensors for diesel systems COMMON RAIL type BOSCH

Bosch COMMON RAIL performance direct fuel 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 fuel injection pump of a certain class and level:

• with control valve on the high pressure rail;
• adjusting the fuel on the high pressure pipe when exiting to the injection pump;
• “double control” type, with two RTDs on the high and low pressure lines.

Diagnostics and malfunctions of the fuel regulator

Fuel pressure regulator
The design of the fuel pressure regulator does not allow for repairs. In some cases, it is cleaned, but this procedure does not briefly extend the life of the device. If a breakdown is detected, most often the regulator is completely replaced with a new one. The main types of faults of this unit are:

• sagging or breakage of the working regulator spring;
• depressurization of the housing;
• mechanical wear of contact surfaces;
• corrosion of various surfaces;
• channel contamination.

Direct malfunctions can manifest themselves in three formats:

1. jamming - the regulator does not operate every time it is needed, but periodically;
2. incomplete closure - fuel is constantly drained into the tank (return line), regardless of pressure;
3. jamming in the closed position - fuel does not drain under any parameters.

Signs of a malfunctioning fuel regulator have much in common with fuel pump failures and dirty filters. Thus, preliminary diagnosis can be made based on the following observations:

• Unstable operation and engine stopping in idle mode.
• Increased fuel consumption.
• Reduced motor power.
• Slow response to pressing the throttle pedal.
• Lack of smooth movement when accelerating the car, jerking is observed.
• The content of harmful components CO and CH in the exhaust increases significantly.
• The car does not accelerate.

The quality of the fuel has a significant impact on the service life of the fuel pressure regulator. You should also not neglect the timely replacement of fuel filters. Particular attention should be paid to the fuel regulator if the car has not been in use for a long time.

Causes of malfunctions

There are not many reasons why the fuel regulator fails. The element cannot be called ultra-reliable; it works, as they say, under wear and tear, and is very dependent on the quality of the fuel.

Causes of breakdowns:

1. Marriage. This is not a common reason, but sometimes you come across defective products from domestic automakers. It is recommended to check the spare part before purchasing.
2. Wear. Usually observed after 100-200 thousand kilometers. In the regulator, the membrane becomes less elastic, the pressure control valve gets stuck, and the spring becomes weaker.
3. Bad fuel. Gasoline and diesel car engine fuel often contains too much moisture, debris, and foreign toxins. Water in fuel causes rusting of the metal parts of the regulator. Increasing over time, they interfere with its normal functioning and lead to weakening of the spring.
4. The fuel filter is clogged. Garbage fractions in the fuel clog the system, including the RTD, and become clogged. This leads to spring wear and valve jamming.

On a note!

RTDs are usually not repaired, but replaced with a new one. But, if the cause of the breakdown is clogging, it can be cleaned.

Symptoms of element failure

During the operation of the car, a car owner may encounter two types of RTD failure:

1. The pressure drop in the rail is below the permissible level - the regulator directs most of the fuel through the return line to the gas tank.
2. Increase in pressure to maximum - the element does not allow fuel to flow into the return line.

Note. As a rule, the first malfunction is accompanied by a rapid drop in pressure in the system after the electric fuel pump is turned off.

It is quite simple to track the signs of the first malfunction - the power unit is sorely lacking fuel for normal operation in all modes. Symptoms appear as follows:

• cold starting is difficult, the engine runs extremely unstable until it warms up;
• “dips” during acceleration and jerks when moving uphill;
• the car often stalls at idle;
• Gasoline consumption per 100 km increases.

The increased fuel consumption is explained by the actions of the driver trying to compensate for the lack of fuel mixture by pressing the accelerator pedal. Driving in this mode is quite difficult - it is better to immediately check the fuel pressure regulator for functionality.

When the valve does not allow excess fuel to flow into the tank, the following consequences are observed:

1. Due to too high pressure from the ramp side, the injectors begin to leak and fill the cylinders with pure gasoline, and not with the working air-fuel mixture.
2. The engine is bad, it emits black smoke from the exhaust, and sometimes you can hear popping noises in the exhaust manifold. The reason is flashes of unburnt fuel.
3. Consumption increases noticeably.
4. Leaks may be observed at the joints of the fuel pipes, and a strong gasoline smell may be felt.

Practical experience shows that a lack of fuel mixture occurs more often than an excess. That is, the most common problem with an RTD is the draining of gasoline into the return pipe and tank.

Video

Problems with the RTD: it doesn’t drive well, it doesn’t accelerate, it jerks.

How to check the fuel pressure regulator. Example on a BMW E34 (BMW E34).

How to measure the pressure in the fuel system on a VAZ 2110 car.

Violation of the integrity of the body

Poor quality fuel, the presence of foreign impurities in it and other negative factors contribute to the destruction of the hull. The device stops working normally. Detecting a small fluid leak is quite difficult. This is due to the fact that gasoline evaporates quickly. Smudges and stains form at the installation site.

If a violation of the integrity of the housing is detected, the product should be replaced immediately. A leak may cause a fire.

Signs of sensor failure

In all cars produced after 2000, the RTD is integrated into the engine control unit and in case of any malfunction, a “Check” will light up on the dashboard. There are old diesel engines that are equipped with mechanical regulators; diagnostics of the elements is carried out as planned or after a malfunction of the internal combustion engine occurs. Characteristic symptoms of a faulty sensor:

• In addition to the “Check Engine” signal, the following error codes appear: P0190-P0194.
• A sharp decrease in internal combustion engine power, loss of traction, is often detected during overtaking; the car does not have the power to dynamically accelerate even up to 120 km/h.
• Excessive fuel consumption.
• The car starts poorly, 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.

Signs of RTD malfunction

The mechanical regulator is a reliable element due to its simplicity of design. But it also breaks. A malfunction of the RTD is manifested by a number of symptoms:

1. Difficulty starting the engine.
2. Instability and “swimming” of revolutions.
3. Reduced power and dynamic performance of the car.
4. Spontaneous stop of the unit at idle.
5. Jerks and jerking of the car when changing the engine operating mode.

Malfunctions of other components of the injection system also give the same symptoms, which makes it difficult to identify the cause of incorrect operation of the power unit.

At the same time, when searching for a problem, car owners do not even pay attention to the RTD, believing that there is nothing to break in it

Regulator malfunctions:

• reduction in spring stiffness;
• valve jamming (RDT functions spontaneously and haphazardly);
• valve jamming;
• clogged channels;

The pressure regulator is considered maintenance-free, and if a malfunction is detected, it is replaced.

Something else useful for you:

• Why does the engine pick up speed, but does not pull when driving?
• IAC (idle air control): what is it and what is it for?
• How to replace the idle air regulator on a VAZ 2108, 2109, 2114?

How to check the fuel pressure sensor

Depending on what fuel supply system is used for the car, there are three ways to check the sensor for functionality without dismantling the fuel rail:

• mechanical method for old-style cars with rubber fuel discharge hoses for gasoline internal combustion engines;
• multimeter;
• pressure gauge.

Dismantling the rack 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 together with the DDT. In most cases, diagnostics are carried out at a service station, since you will need to use a special stand. Self-diagnosis in the garage without dismantling the rack requires a tester and is carried out in 15 minutes.

Mechanical diagnostics of an old-style regulator

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

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

If the fault is in the regulator, the engine will restore its operation, the speed will become smooth, and jerking will disappear. If, after the outlet pipe is closed, the motor continues to operate incorrectly, the fault may be in clogged filters or worn contacts, although the sensor is working properly.

Diagnostics with a multimeter

Using a tester, they check the performance of the RTD and the quality of power from the block. 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 black lead of the tester to “minus”, attach the red probe to the connector of the block.

Diagnostics

There are a number of methods to diagnose the condition. All of them are simple, even a novice car enthusiast can handle them.

Test methods:

1. Visually. This is an option for carburetor engines. Pinch the valve or disconnect it. The fault can be determined by how intense the fuel flow is. The method is simple, but inaccurate.
2. Pressure gauge. Install the device between the fitting and the hose, temporarily disconnecting the vacuum hose. The reading on the pressure gauge should rise to 0.7 bar.
3. By pinching the hose. Check the RTD by clamping the return line. The pressure gauge should respond immediately. If the engine does not rev up, the governor is faulty. Start the engine by clamping the return line. Watch the speed and listen to his work. If its operation is uniform, the adjustment valve is faulty - it must be replaced.

The procedure for checking the performance of an RTD depends on its type - mechanical and electrical components are checked differently.

How to check a mechanical regulator:

• locate the fuel return hose under the hood;
• start the engine - let it run for a minute to warm up a little;
• using pliers - very carefully, pinch the return hose;
• if after clamping the engine begins to work well, then the problem is a broken RTD.

It is forbidden to pinch the hoses for a long time - this creates additional stress on the pump, which leads to its breakdown in the future.

In injection engines, fuel hoses are made of metal rather than rubber to increase reliability. Electrical sensors in such systems are made on the basis of strain gauges. To determine if the RTD on the injector is faulty, check the voltage at the sensor output.

In diesel engines, RTDs are checked by measuring the resistance of the sensor inductor. Usually the normal value is around 8 ohms. If the resistance is noticeably higher, or vice versa, much lower than stated, the regulator is broken. Detailed diagnostics are carried out only in the service center - at special stands where sensors and the entire fuel supply system are checked.

How to change RTD

The RTD is usually replaced with a new one, but you can try to repair it. You can buy the required unit at any auto store or on one of the online sites that sell spare parts.

Procedure:

1. Locate the pressure control plug under the hood. After unscrewing it, unscrew the spool.
2. Connect the hose and pressure gauge. Use a clamp. Maximum pressure – 3.2 Bar.
3. Unfasten the hose from the RTD. With this procedure, the pressure increases from 20 to 70 kPa. Otherwise, the repair turns out to be unnecessary, you need to install another unit.

If the RTD is not repairable, replace it with a new part:

1. Unfasten the vacuum line. The pressure will increase. First lower it and then remove the hose. Unscrew the nut on the drain pipe through which gasoline or diesel fuel flows to the regulator through the filter.
2. Unscrew the fastenings of the unit to the ramp. Remove the unit from the line through which fuel is discharged. Remove the ring remaining in the ramp to fit it onto the RTD before mounting.
3. Install a new RTD and perform the above steps in the mirror sequence. Check if the new unit is working properly and complete the assembly. After installation, check the quality of operation of the new device.

RTD is a miniature but extremely important part of the car. By regularly checking its readiness for work and changing it on time, it is possible to prevent many problems that car owners often encounter.

Repair and replacement of RTD

If your vehicle exhibits any number of symptoms of fuel regulator malfunction, diagnosing the fuel regulator is the only step toward returning it to proper operating parameters. In the event that a check indicates that the device is out of order, the following must be done.

Step 1. Remove the fitting plug to be able to control the pressure of the flammable liquid at its end.

Step 2. Using a special metal protective cap, carefully remove the spool from the inner cavity of the fitting.

Step 3. Reduce the pressure in the power system, and then carefully remove the vacuum hose from the device.

Step 4. Remove the nut used to secure the fuel supply tube.

Step 5. After the two bolts that secure the module to the fuel frame are unscrewed, you need to smoothly remove the fitting from their holes.

Step 6. Carefully remove the RTD.

As a rule, the removed device cannot be repaired, and it is replaced with a new, more functional one. You can purchase a module with delivery either in any specialized store or via the Internet.

Doesn't show fuel level AT ALL

When the arrow points to “0” with a full tank, then attention should be paid to all contacts and connections:

1. First of all, this concerns the bolts located on the back side of the instrument panel, since they are the ones who create contact by fixing on the indicators.
2. It is possible that the fuel level needle has lost its position and needs to be adjusted.
3. The instrument panel itself may also be faulty. Since its mechanical parts are very susceptible to wear.
4. We test all the “negative” wires, especially the one located near the handbrake. Because often it is he who is promoted.
5. The float or the FLS itself is jammed.

Having analyzed all of the above, we can come to the conclusion that this whole problem lies entirely in the power supply system and the mechanical part of the fuel level sensor.

Please note that if you have an on-board computer (not older models - approx.), it is possible to control the fuel level electronically. You just need to enter the readings after each refueling of the car and the faulty FLS needle will no longer bother you.