Fuel pressure regulator valves

Fuel pressure regulator(FPR)

What is a FPR? What does it do?

A  fuel pressure regulator is a solenoid valve. FP Regulators are fitted to high pressure pumps and or  to the common fuel rail in modern common rail diesel cars.

The function of the FPR is to keep the pressure in the rail at a constant level

Probably  the most common make is Bosch.

A  fuel  pressure sensor signals the pressure in the fuel rail to the ECU – the ECU in turn signals the regulator to open or close.

“The rail contains a pressurised supply of diesel fuel ready for the injectors to use; when the pressure in the rail drops the sensor signals this to the ECU and pressure (via the pump) is restored.”

The ECU  controls the  supply of  fuel  to the rail from the high pressure pump;
it does this by means of the Fuel pressure control valve.
If pressure is getting too high the regulator opens to allow fuel to return to the tank (and pressure drops) It works the opposite way when pressure falls.

What does a fuel pressure regulator look like?

Some Fuel pressure regualtors  screw  into the common rail like the one pictured above
It is easy to remove (when the engine is switched off) simply remove the electric male connecting plug and unscrew in a conventional way.

Other regulators are held in place by two or three bolts.
fuel pressure regulator

Mercedes FPR

bosch fuel pressure regulator

Bosch FPR

These are often found in place on the high pressure  fuel pump (mounted on the engine)

Why is the Fuel pressure regulator different?

FPR’s are different. Look out for different internal endings (eg the 2 regulators pictured here) , different female plug fittings and different mounting bolts.

What other types of sensors/regulators are there on a diesel engine?

The Fuel pressure regulator is  a solenoid  i.e.  it switches on and off to control and maintain the fuel pressure level.
It senses the pressure of the fuel in the common rail. There are other sensors on the engine including:

  • crank position sensor
  • cam position sensor
  • air flow meter/ sensor
  • temperature sensor
  • boost pressure sensor

Does the Fuel pressure regulator go wrong?

Yes. The fuel pressure regulator is  prone to failure.

How will I know if  the FPR is faulty?

Common symptoms of Fuel pressure regulator  failure are
cutting out,
difficult to start,

If the regulator is faulty you will get an error code indicating this when you do a scan on the engine.

Is it easy to replace?

Yes it is easy to replace and you will not need to recode the engine.
You may however need to cancel fault codes in the ECU memory

Do I  have to fit ‘like for like’?

Yes you do have to fit ‘like for like’.
If the id numbers of a replacement Fuel pressure sensor correspond to the original then it can be used.
Bosch numbers are 10 digit starting 0281 002 – – –
Siemens also use 10 digit numbers like 9658227880 and id’s like 55PP06-03
These numbers are printed on the sensor or stamped into the plastic

What are the different makes? Which vehicles are they fitted in?

Bosch, Siemens/Delphi, Denso (Japanese) are the main makes of fuel pressure sensor.
As with other types of electronic components there are no hard and fast rules .
Denso are fitted into Mazda, Toyota, Nissan.
But you will find Bosch regualtors  fitted in Kia, Hyundai, etc.

How can I identify which FPR fits my vehicle?

You will need to establish the make and  identity  number.
It’s best to get this from the regulator itself to avoid incorrect replacement.

Where can I buy a replacement?

Diesel Injectors UK carry a large range of fuel pressure regulators of all makes.
The aim of this page is to provide more information about fuel pressure regulators and id numbers

Summary: Fuel pressure regulators – and how to identify them.

The fuel pressure regulator is sometimes screwed into the common fuel rail (solid rail –  fuel injector feed pipes also bolt to this rail) .
Removal and fitting does not require special tools.
Replacement regulators do not normally require coding
The fuel pressure regulator is  prone to failure.

Bosch, Delphi, Siemens and Denso…

In European cars the most common make is Bosch;  followed by Delphi and Siemens and then Denso