Do I need an aftermarket lift pump to use the fuel pressure gauge on my 2014–2019 Duramax?Updated 4 hours ago

 It depends on which engine your truck has.

For 2014–2016 LML Duramax models, the factory fuel system is vacuum-driven, meaning the CP4 injection pump draws fuel from the tank under vacuum rather than using a factory supply pump to create positive pressure. Because of this design, an aftermarket lift pump is required for the fuel pressure gauge to read accurately and consistently.

For 2017–2019 L5P Duramax models, the factory fuel system includes a low-pressure supply pump that pressurizes fuel before the filter housing. Since the system already produces positive fuel pressure from the factory, an aftermarket lift pump is not required for the gauge to function properly.

Many aftermarket lift pump systems also include a dedicated port for a fuel pressure sensor, allowing the gauge to monitor low-side fuel pressure directly from the pump system if installed.