Oil Pressure Gauge: Description and Operation

Oil Pressure Gauge:

The oil pressure gauge indicates the pressure of the lubricating oil provided by the engine oil pump. The oil pressure gauge sending unit is a variable resistor mounted to the front of the engine so it will sense the oil pressure in a main oil passage just downstream form the engine oil pump. When electric power is supplied to the gauge current flows through the gauge to the resistor in the sending unit and then to ground. The position of the oil pressure gauge pointer is determined by the strength of the current flowing through the gauge.

When oil pressure is low the resistance of the sending unit also is low and current flow through the gauge is high. This cause the gauge indicator needle to show a low pressure reading. As oil pressure increases the resistance of the sending unit resistor also increases and current flow through the gage is reduced. Under normal conditions the oil pressure reading should be between 138 to 414 kPa (20 to 60 psi). Engine oil pressure never should fall below a reading of 28 kPa (4 psi) even at idle.