The Fuel Pressure Relief Valve (PRV) on heavy equipment and generators is usually found on the high-pressure pump or on the common rail. This pressure relief valve is responsible for regulating the fuel pressure in the fuel rail. Common rail injections systems run anywhere between 23,000 to 29,000 PSI – if fuel pressure rises above this the Fuel Pressure Relief Valve will open to allow that overflow pressure to escape into the return system.  

Possible Causes for Faulty Pressure Relief Valve

The valve is designed to relieve pressure in the system. Each time this happens this creates “counts” in the engine control module (ECM) until it reaches a point where it will give you a fault code and begin derating.    

Usually if you have a faulty pressure relief valve on a piece of construction equipment, farming/agriculture equipment or generator you will see one of the following fault codes for Deutz engines: 825-833 and 876 or an SPN of 523470 and 523009.

Signs that you need to replace the valve are:

• Hard/no starts
• A reduction in power and accelerations
• Below average fuel efficiency
• And of course fault codes

Maintenance goes a long way on these fuel systems so make sure you follow your manufacturer's guidelines for fuel filter replacement and keeping those water separators drained.

How Do I Check if My Heavy Equipment Fuel Pressure Relief Valve is Bad?

When fuel pressure relief valves (PRV) fails it can cause damage to the engine. If left unchecked it could result in reduced engine power (derate) or a no start condition. To see if the valve needs replacing you should first check to see if it has logged counts into the ECM. If it has, you then need to investigate why this is happening. This can be from maintenance neglect, high pressure pumps, metering units, blocked return lines, fuel pressure sensors or the PRV itself.

Other things to look for:

• If you have a fault code, test the wiring from the ECU to the pressure regulation valve.
• See if there is mechanical damage to the engine or fuel system.
• Make sure the ECU has proper power supply

How to Clear a Pressure Relief Valve Fault Code

To clear this code you will need to replace the pressure relief valve and reset the fault with a help of a dealer or with the use of a diagnostic tool. For this demonstration we will performing the reset on a Deutz using a Diesel Laptops Diagnostic Kit with Cojali Jaltest Off-Highway Software. This software allows us to do repairs on all of the makes and models of farming and construction equipment that we regularly work on. 

Once we log on to the software, we select our engine type:

Stationary engines -> Deutz -> TCD 3.6 -> EMR4 – EDC 17 -> Electronic Diesel Control -> Common Rail

You are able to reset under the ‘DIAGNOSTICS MENU’ by selecting ‘MAINTENANCE’

• Choose ‘PRESSURE RELIEF VALVE RESET (PRV)’
  • You can do either the automatic or manual process, for this demonstration we will go through the steps for manual
• Make sure that the engine is not running
• Change the count to ‘0’
• Once that has processed we will exit out and go back to ‘READ FAULT CODES’ where you will be able to see that the code is inactive and you can clear the fault from this menu.

To take a look at what all the Diesel Laptops Off-Highway kit can do, click here.