Running Losses Solenoid

Running Losses (Three - Two Way Valve):

Running losses refers to the fuel vapors that can escape to the atmosphere during vehicle operation. The fuel tank is the major source of running loss vapors. The redesigned fuel pressure regulator with by-pass solenoid was introduced on the 1995 325i and is now incorporated into the MS41.1 engine management system.

With the engine running, the volume of fuel flowing through the fuel rail is more than the engine can consume. The fuel passing through the fuel rail is heated by the engine and is returned to the tank.

Using the by-pass type regulator reduces the fuel heating thereby reducing the temperature of the fuel in the tank. This lowers the amount of vaporization that takes place.

Solenoid Energized - Port Closed:

Solenoid De-Energized - Port Opened:

OPERATION
The MS41.1 control module controls the operation of the by-pass solenoid. The solenoid is energized for 20 seconds on engine start up to purge air bubbles.

After twenty seconds, the solenoid is switched OFF and the by-pass is opened.

This allows the majority of the fuel to by-pass the engine compartment fuel rail thus lowering the temperature and amount of vaporization that takes place in the fuel tank.