Low Pressure Regulator

The Low Pressure Regulator (LPR) is a negative pressure two-stage configuration that is closed when the engine is not running. When the engine is cranking or running a partial vacuum is created in the fuel line to the regulator. This opens the regulator, permitting fuel to flow to the fuel mixer.

The regulator receives CNG fuel at about 170 psi. The pressure is reduced in two stages to slightly less than atmospheric. In the first stage the pressure is reduced to approximately 5 psi. In the second stage, the CNG fuel is drawn into the secondary chamber where the pressure is reduced to approximately -0.5 in. of water column.