The working end of the probe is a rigid metal tube filled with rubber in which two wires attach to a piezoelectric crystal.
Low oil sensor principle of operation
The elctro-vibration oil sensor for gasoline engines consists of a constant vibration sensor and a delayed reaction controller.
When immersed in oil the vibration plate moves slowly against the sensor probe. As the level falls, less oil cushions the vibration plate allowing it to move faster in the probe. This increased movement generates a signal to the controller indicating low oil level.
The controller is powered by the exciter coil in the magneto. The controller monitors signals from the sensor, and delays engine shutdown until a predetermined number of signals has been exceeded. In this way unwanted shutdowns, such as those by operating on an uneven surface, are reduced. When sufficient signals have been received the controller shorts the primary current from the ignition coil to ground stopping the engine.
The vibration sensor probe is connected to the controller by a shielded cable containing two wires. The yellow and yellow/red wires go to an optional LED indicator light. The black/white wire goes to ground and the black wire goes to the ignition coil and/or the exciter coil of the magneto.
Wiring diagram for Wisconsin Robin EY27 and EY25 Oil Sensor
Troubleshooting Electro-Vibration Type Sensor
Oil Sensor stops gasoline engines. Figures 2-2 and 2-3
1. Check oil level. Fill crankcase to maximum level on dipstick.
2. Inspect and repair all loose, broken or corroded wires.
3. Check sensor (Figures 2-2 and 2-3).