Control Solenoids

FUEL CONTROL SOLENOID (FCS)
The FCS is an electronically controlled solenoid used to trim fuel mixtures by metering air valve vacuum to control the pressure on top of the LPR secondary diaphragm. This changes the LPR output pressure, and the amount of fuel flowing out of the LPR. The Alternative Fuels ECM controls the FCS with an electrical duty cycle which is converted into the regulated air valve vacuum signal communicated to the top of the LPR. As the FCS duty cycle increases, more vacuum on top of the LPR secondary diaphragm reduces the fuel flow out of the LPR which leans the air fuel mixture. As the FCS duty cycle decreases, less vacuum on top of the LPR secondary diaphragm increases the fuel flow out of the LPR enriching the air fuel mixture. The fuel control authority of the FCS increases with engine air flow.

IDLE CONTROL SOLENOID (ICS)
The ICS is an electronically controlled solenoid used to meter supplemental fuel from the LPR to the mixer to increase fuel control authority during idle and low speed operation. The Alternative Fuels ECM controls the ICS with an electrical duty cycle which is converted into the regulated fuel flow from the LPR to the mixer. As the ICS duty cycle increases, more supplemental fuel flows out of the LPR into the mixer enriching the air fuel mixture. As the ICS duty cycle decreases, less supplemental fuel flows out of the LPR into the mixer which leans the air fuel mixture. The fuel control authority of the ICS decreases with engine air flow.