Fuel pressure regulator return line.

[Snakebit]

Installed my Webers. Using a Mallory fuel pressure regulator rated 3to 9 lbs. The fuel line is AN6 and the return line is AN4. Fuel pump is a Carter mechanical street pump putting out 6lbs. I can not get the pressure to adjust below 6 lbs. It should be around 3 lbs or less for Webers. Any sugestions other than tearing apart half the car to install an AN6 return line?

[Gaz64]

Originally Posted by Snakebit

Installed my Webers. Using a Mallory fuel pressure regulator rated 3to 9 lbs. The fuel line is AN6 and the return line is AN4. Fuel pump is a Carter mechanical street pump putting out 6lbs. I can not get the pressure to adjust below 6 lbs. It should be around 3 lbs or less for Webers. Any sugestions other than tearing apart half the car to install an AN6 return line?

Two things:
1. I'd run a temporary larger return into a bucket and see if it proves AN4 to be too small. Or you have a restrictive fitting somewhere.
2. Maybe your mechanical pump pulses and the bypass reg is oscillating and unable to control the bypass volume. I run a Mallory gerotor 140G/hr electric pump. Smoother fuel flow from the pump.

[Caprimaniac]

My guess is: too tight return lines. I run a Aeromotive regulator and they advice 1/2" return line (corresponds to AN8..) for my application (engine front, tank rear, carb at 3 psi).

Gary have some great suggestions. Should be tried.

[Snakebit]

Changed to a 6AN line and used a lighter spring. Solved the problem.