Common Rail High Pressure Relief Valve
This is the pressure relief valve located in the driver's side fuel rail on the 2004.5 - 2007 Duramax LLY & LBZ engines. These valves are known to go bad and open prematurely causing a "fuel rail PSI low" problem. Once a valve is weakened it tends to get worse. Replacing the valve with a new one is much safer than shimming it and taking your chances with the high (22,000+ PSI) pressures that this valve was designed to protect from. I recommend the LBZ version in the LLY trucks due to the slightly higher, but still safe, opening PSI.
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