Running Losses 3/2 Way Fuel Rail Solenoid Valve

The engine 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.







The solenoid is also activated momentarily if an engine misfire is detected. This function provides full fuel flow through the fuel rail to determine if the misfire was caused by a lean fuel condition.







This component was also equipped on a few 1995 325i vehicles. The M3.3.1 engine control system of this vehicle did not control the solenoid valve. The valve was controlled by a separate relay module which monitored KL 50 signal and provided operation of the valve for 20 seconds.