What Does a Suction Control Valve Do?

A Suction Control Valve (SCV) regulates fuel pressure in common rail diesel (CRD) engines. Having correct fuel pressure when driving is essential to efficient operating of a vehicle and an overall healthy engine. The engine control unit (ECU) reads the information from the suction control valve, so often any problems with the SCV will light the malfunction indicator lamp.

When your suction control valve is in good working order the supply pump only uses the exact amount of fuel needed to maintain the rail pressure, reduces emissions, and lowers fuel flow as the engine runs. The suction control valve (SCV) is located on the back of the high-pressure supply pump or fuel pump.

Suction control valve location inside engine bay diagram

What Are the Signs of a Bad Suction Control Valve?

A faulty suction control valve may be caused by certain fuel conditions like low quality or contaminated diesel fuel. A few of the codes from the Engine Control Unit (ECU) that have to do with a bad suction control valve are P0089 (Stuck SCV), P0628 (Open SCV), and P1275 (Supply Pump Exchange). These codes are for Montero Sports vehicles and will differ with the brand of your car, SUV, van, or truck. Look up the error codes for your automobile model.

Here are few other symptoms of a bad SCV that are harder to detect, especially when the malfunction indicator does not turn on.

1. Sudden Engine Shut Down - One of the first signs of an issue with the suction control valve is when the engine suddenly shuts down immediately or within a few minutes after starting your car. When the SCV is damaged, the fuel pressure disappears. The loss of fuel pressure from a damaged SCV causes the sudden shutdowns in a diesel fuel engine.

2. Easy To Start Yet Tough To Run - Another common symptom of a bad suction control valve is when your engine has trouble running even when you can start your car without problems. Eventually, your engine will shut down as you try and run your car as the fuel pressure cannot be regulated and will drop.

3. Gas Fully Open with Engine at Constant Revolutions Per Minute - If your engine is stuck at a 1500 to 2000 RPM with a full gas tank, your SCV could be damaged or faulty. This symptom of bad suction control valves often does not come with other engine problems except for it being less powerful. This occurs when the fuel pressure is imbalanced, and the engine needs to run on low power because of that difference.

Final Thoughts

Now that you understand what your suction control valve (SCV) is and what can cause problems. You can keep an eye out for signs that this car part is malfunctioning or damaged. If you have realised that your SCV is malfunctioning and you need a new one, browse our selection of auto parts for your car here.