Low pressure of oil
During ignition, the signal lamp goes on which indicates low pressure in the system. Start of the engine results in increasing the pressure of oil in the system. Rapidly increasing pressure deforms the membrane of the sensor which upon reaching the set pressure opens the electric circuit and the indication light goes off. In cars equipped with a dial indicator, the hand moves quicker during ignition from zero to the field marked as correct for normal working of the engine.
If after a few seconds from starting the ignition the low pressure indication light does not go off or the hand of indicator does not reach the normal pressure level, the engine should be switched off immediately and the level of oil checked and replenished if necessary. If the indication light does not go off with the right level of oil the following reasons should be considered:
There is a malfunction in the oil pressure indicator
The conduit between the indicator and sensor may be damaged
The oil pump is over oiling
Oil inlet from the oil sump into the pump may be blocked
The overflow valve regulating the oil pressure in the system is blocked in the open position
When the indicating light does not go on both when turning the key in the ignition switch and when trying to start the engine, the indication light, pressure sensor and the conduit should be checked and repaired without delay.
In some engines the oil filters are installed in a manner allowing oil dropping from the filter during the working of the engine. Such a case is shown in picture 2, where filter is screwed to the engine in a horizontal position and also above the oil level in the oil sump. In normal conditions, filling the filter and the system with oil takes about 5 seconds. While the indicators will show low oil pressure.
Filters specially designed for work in that position are equipped with an internal anti-drain back valve. When the engine works, this valve protects oil dripping from the filter which efficiently shortens the work of the engine with low oil pressure during ignition and shortly after. The valve usually resembles a rubber gasket and is visible through holes in the cover of the filter.
In some conditions the low oil pressure indicator may alternately go on and off. It happens that such signs occur during driving on curves or up and down steep slopes. The reason is the low oil level in the oil sump. During tilting the end of the suction pipe is not continuously immersed in oil and the pump sucks the air. In such cases the oil should be replenished without delay. To summarise, devices signalling low oil pressure in engines provide valuable information for drivers as to the technical state of cars. Driver’s reaction to indications with regards to low oil pressure during the working of the engine should be very quick – the engine should be shut off immediately and the reason of malfunction checked. Continuation of driving endangers with a serious damage to the engine.
Prepared on the basis of Filter Manufacturers Council – Technical Service Bulletin 83-2R2