Diagnosing Common Rail Diesel Faults – the Suction Control Valve

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As was mentioned in an earlier post, the suction control valve plays a critical role in the common rail diesel injection system, and is also one of the “usual suspects” in common rail diesel faults.

For the average owner, looking to diagnose an issue with his vehicle, we are going to explain here the part the suction control valve plays in fuel delivery, and why when you start trying to diagnose common rail diesel faults, you should often start here, rather than the injectors. For the pros and smarties among us, let Matt Bailey explain the suction control valve in a little more detail.

Whats an suction Control Valve actually do?

The suction control valve in the common rail fuel system basically acts as the throttle to the fuel pump, conserving energy in the system by allowing only the required amount of fuel to be pumped through the system. When a technician who is not a pro is trying to diagnose common rail diesel faults, the suction control valve is often overlooked, when in many cases, it should be the starting point.

The suction control valve, like every other part in the later common rail diesel injection systems, operates at tight tolerances. Fuel contamination and wear inside the valve means that the ECU cannot command the correct fuel pressure to the injectors. Keeping in mind the incredible pressure (thousands of psi) inside the fuel rail, and that a faulty valve means that pressure is jumping around quite extremely, it makes sense that when diagnosing common rail diesel faults that involve drive-ability, this should be one of the first places the technician suspects.

Some of our customers have experienced their truck going into “limp mode”, and that is often due to the fuel pressure varying one way or the other past a limit set by the ECU. After a few hundred sessions of stopping, turning off the switch, and restarting to reset the computer, it is time to head for the shop, where you either get a pro, who starts with the suction control valve (not cheap, but not reeeally expensive) or you get one that heads right for the injectors. The fact is, when diagnosing common rail diesel faults that involve drive-ability, replacing the suction control valve should be the first place you check, as it is relatively inexpensive, and as we said before, it is a wear item, just like the injectors, and crossing it off the list of maintenance items for your common rail diesel is a good thing in itself.

If you think this might be your issue, click here to see our full range of SCVs available from BDG http://melodyj2.sg-host.com/product-category/suction-control-valves/

If you are still reading, check out the video above to learn a little more about the part this valve plays in the common rail injection system. The average guy may not follow the whole plot, but watching the video, you know that Baileys truly knows common rail injection.