Oil Pressure Gauge

The oil pressure gage indicates the pressure of the lubricating oil flow provided by the engine oil pump. The oil pressure gage sending unit is a variable resistor mounted to the engine block so it will sense the oil pressure in a main oil passage just downstream from the engine oil pump.

When electric power is supplied to the gage, current flows through the gage to the resistor in the sending unit and then to ground at the engine block. The position of the oil pressure gage pointer is determined by the strength of the current flowing through the gage.

When oil pressure is low, the resistance of the sending unit also is low and current flow through the gage is high. This causes the gage 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 he between 138 and 414 kPa (20 and 60 psi). Engine oil pressure never should fall below a reading of 28 kPa (4 psi), even at idle.

The oil pressure gage contains internal coils that create magnetic fields when current flows through them. The current through the coils varies depending on the Oil Pressure Sensor resistance. (Low pressure resistance is approximately 10 ohms, high pressure resistance is approximately 90 ohms.) The varying sensor resistance causes the current through the coils to fluctuate. The magnetic fields of the coils move the pointer.