1999 Ski-Doo Factory Shop Manual Volume Three, Page 159Get this manual
Section 04 ENGINE Subsection 08 (CARBURETOR AND FUEL PUMP)
Enrichment Solenoid
Solenoid Operating Principle solenoid is winding coiled in order to produce magnetic fieldA metal rod crosses the coil and cuts the magnetic fieldEach time the coil is activated, the magnetic field attracts the rodIf the supply current is interrupted, spring pushes the rodSolenoid Function within the DPM System The MPEM turns the solenoid on and off 10 times per second, which means that it operates at 10 cyclessecond or 10 Hertz (Hz)The solenoid therefore opens and closes 10 times per second, thus allowing the pump pressure to reach the distribution gallery (upper tube)For the pressure to vary within the bowls, the solenoid is activated in part by the MPEM during each cycleThis is what is called the duty cycleIn other words, the solenoid will not open throughout the whole cycleThe duty cycle depends on the engine temperatureThe colder the engine, the longer the duty cycleTherefore, the solenoid will stay open longer, thus giving way to pressureMPEM reads engine temperature at once (when starting) through sensor