Bosch Pressure Relief Valve (PRV) 01-04 GM 6.6L Duramax LB7

Is your LB7 Duramax getting hard to start or feeling like it doesn't have the power it used to? Its likely that the pressure relief valve located on your Function Block needs to be replaced. This Pressure Relief Valve (PRV) is responsible for controlling high pressure fuel and bleeding off excessive pressure back into the fuel system when warranted. Because the valve is just a simple spring, it can wear out, causing pressure to be relieved too early, and when this happens the function block is unable to build proper pressure to fire the injectors properly (or at all). There are a few ways to check if your PRV needs to be replaced. First, using a scan tool, you can check for actual rail pressure and comparing to desired rail pressure, and if the actual rail pressure is signicantly lower than desired, it may be that your valve needs to be replaced. Further, some will remove the return line located on the valve and start the truck, seeing if fuel is bypassing while not under load, as it shouldnt' be until higher pressures are achieved. If fuel is bypassing, then it needs to be replaced.