YD25 Suction Control Valves

Suction Control Valves for Nissan Navara’s yd25 engine

All common rail engines use a suction control valve (SCV) or metering unit which is responsible for controlling fuel pressure in them. The SCVs use extremely fine tolerances and are quickly affected by dirt and contaminated fuel. When the SCV is affected by wear or dirt, they will cause the common rail pump to deliver an inconsistent fuel pressure to what is being demanded by the factory ECU. ECUs’ ability to control the rail pressure is quite limited under these circumstances. This problem occurs consistently in Nissan Navara; particularly the models with the D40 engines. These models can suffer from malfunctioning SCVs, causing running issues such as a sudden lack of power, which can be intermittent.

Long-term solutions for faulty SCVs

Though cleaning or rotating the SCV at 90 degrees may fix the problem for a short period, sooner or later the SCVs will need to be replaced. You can also reset the normal operating condition by stopping and re-starting the engine. However, the problem will re-appear in a short while.

The control valves which are fitted to the high-pressure fuel pump are replaceable items. At Baileys we check and replace SCVs as a mandatory item after the vehicle crosses 60,000-80,000 km. We also recommend a relearn of the factory ECU that is done every time the fuel filter is changed so that it finds the correct operating fuel pressure.

Check the injector from time to time

A small fluctuation of rail pressure can create a huge variation in engine performance and the engine will experience surging as the ECU tries to find the correct operating fuel pressure. If the varying pressure moves past a pre set limit, the vehicle will go into limp mode. In order to get the best result from the engine performance, it is advised to change both the SCVs and injectors at the same time.

As SCVs ensure the smooth operation of the rail fuel injection system, it is important to ensure that your replacement suction control valves and injectors are of the highest quality. It is easy to remove a SCV and check the valve piston which should be ideally smooth and clean like chrome. However, it is generally found with marks and so it’s mandatory to check the valve piston while checking the SCV.

Watch the rail pressure when idle

It is also compulsory to watch the rail pressure fluctuation when the vehicle is idle and hot. At Baileys, checking the rail pressure is part of our pre injector works diagnostics and we would be able to properly assess and detect any sort of rail diesel engine faults.

It is important to ensure that your replacement suction control valves and injectors are of the highest quality. At Baileys, we have solutions for any injector failure and SCV replacement and can ensure that our suction control valves will deliver more power over any other standard unit by allowing the rail pump to make available more fuel for the ECU to take control of your vehicle.

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