Holley Fuel Pressure Regulator - 1-4 PSI Range 3/8'' NPT Ports

Its primary purpose is to reduce and regulate the output pressure from a low-pressure fuel pump to a specific, stable range (1-4 psi) required by most carburetors.

No, this regulator is specifically designed for low-pressure, carbureted applications and is not suitable for high-pressure fuel injection systems.

This regulator is designed for use with gasoline only. It is not suitable for methanol or alcohol fuels.

The fuel pressure is adjusted via a screw on the regulator. Clockwise rotation generally increases pressure, and counter-clockwise rotation decreases it. Always use a fuel pressure gauge to confirm your setting.

This refers to the size and type of thread for the inlet and outlet ports. '3/8"' is the nominal pipe size, and 'NPT' (National Pipe Thread) is a standard for tapered threads used on pipe fittings. 'Female' means the threads are on the inside of the port.

No, the mounting holes are not tapped from the factory. You should use the supplied self-tapping screws, which will create their own threads when installed.

The adjustable pressure range for this specific model (12-804) is from 1 psi to 4 psi.

Ensure the adjustment screw is properly set. Use a reliable fuel pressure gauge. Verify the fuel pump is operating within its specified pressure range and that there are no restrictions in the fuel lines.

Check that all NPT fittings are properly tightened. Use quality thread sealant (like PTFE tape or pipe dope) on all threaded connections. Ensure the correct size fittings are used.

Confirm the regulator is set to the correct pressure for your carburetor. Check for fuel filter blockages, kinks in fuel lines, or vacuum leaks in the intake system. Ensure the fuel pump is delivering adequate volume.

Some minor diaphragm noise can be normal. However, excessive or unusual noises may indicate a problem with fuel flow or pressure regulation. Check for proper installation and fuel pump operation.