LDP Reed Contact Feedback Signal

Introduced on the M5.2.1 and MS41.1 ORVR compliant engine control Systems, the LDP provides a means of testing the fuel/evaporative system for leaks. The pump is activated by ECM control. It pressurizes the fuel tank and evaporative system. The ECM receives a repetitive high/low voltage signal from the LDP as confirmation of LDP functionality and if the evaporative system is holding the pressure.

- The upper chamber contains an integrated reed switch that produces a switched high- low voltage signal that is monitored by the ECM. The switch is opened by the magnetic interruption of the metal rod connected to the diaphragm when in the diaphragm is in the top dead center position.

- The repetitive up/down stroke is confirmation to the ECM that the valve is functioning and the basis for determining if a leak is present in the system. The ECM monitors the length of time it takes for the reed switch to open, which is opposed by pressure under the diaphragm in the lower chamber. The LDP is still cycled, but at a frequency that depends upon the rate of pressure loss in the lower chamber.