Oil pressure control lamp — glows when the pressure in the engine lubrication system is below 0.2 kgf/cm2. Along with the battery charge indicator on the dashboard, it refers to sensors whose readings cannot be ignored. At low pressure, the lubrication system does not perform its functions or does not fully. The heating of rubbing parts increases sharply and their wear accelerates. The engine can fail in a matter of minutes, so its operation with a working oil pressure lamp is strictly prohibited.
The importance of pressure in the engine lubrication system
The engine lubrication system is designed to supply engine oil to rubbing parts for their lubrication, cooling and removal of wear products. In gasoline and diesel internal combustion engines, it works according to two main principles. The first is designed to lubricate the crankshaft, connecting rods and cylinder walls. Oil is captured from the sump by a rotating crankshaft and, flying in all directions, creates a so-called oil mist. This principle is not affected by the pressure in the lubrication system.
The second principle is based on the creation of excess pressure in the system, for which the oil pump is responsible. He takes oil from the sump through the oil receiver, pumps it through the filter, and then pumps it through the channels into the crank and gas distribution mechanisms. Due to this, the crankshaft liners, bearings in the pistons, as well as parts of the gas distribution mechanism - pushers, hydraulic lifters, springs, rocker arms, and so on are lubricated.
Low or no pressure in the lubrication system leads to oil starvation. Friction parts, to which oil cannot penetrate by gravity, overheat and wear out very quickly. The engine experiences thermal overloads that the regular cooling system is not able to cope with. With prolonged use in this mode, the engine jams and fails.
Wiring diagram and operating modes of the oil pressure lamp
To prevent the driver from missing the moment when the pressure in the lubrication system drops below the permissible level, all cars are equipped with an emergency indication. This is a fairly simple system, consisting of only two components - a pressure sensor and a warning lamp.
Oil pressure sensor — consists of a housing, inside of which there is an elastic membrane, a spring and electrical contacts. There is a small hole in the sensor for oil access to the membrane. When a pressure exceeding 0.2 kgf/cm2 is created in the lubrication system, the oil acts on the membrane, overcoming the resistance of the spring. This opens the electrical contacts. Roughly speaking, the sensor in this position does not pass electric current.
Oil pressure warning lamp — located on the dashboard and connected to the battery through a pressure sensor. When the driver turns on the ignition, the pressure in the engine is atmospheric, the sensor contacts are closed — the lamp is constantly on. After starting the engine, the oil pump starts to work, creating excess pressure in the system. The contacts inside the sensor break and the control lamp goes out.
Accordingly, if during engine operation the pressure in the lubrication system disappears for any reason, the driver is informed about this on the dashboard. The oil pressure warning light comes on. To ensure that the alarm does not go unnoticed, this indicator is located in a prominent place on the dashboard and glows in bright red.
Difference between pressure and engine oil level
The engine oil level is a quantitative characteristic that depends on the volume of oil in the sump. May affect system pressure. At a low level, the oil receiver may not "reach" the oil, which is why the oil pump has nothing to pump into the system. Accordingly, the pressure may be unstable or absent altogether. To check the oil level, all engines are equipped with a visual control dipstick (pulled out and looked). On modern cars there is also an electronic level sensor and a corresponding indicator lamp on the dashboard. Unlike the pressure lamp, it shines orange instead of red.
Engine oil pressure is a qualitative characteristic that depends on the efficiency of the oil pump, the condition of the system and the presence of oil. Depending on the design of the engine, sufficient pressure can be generated even when the oil level is below the minimum mark on the dipstick.
For this reason, a pressure warning light cannot replace the traditional method of checking the engine oil level. That is, if this lamp goes out after starting the engine and does not light up during its operation, this is not a reason to ignore the daily check with the dipstick.
And vice versa. If the pressure lamp does not go out after starting the engine or lights up during its operation, then this does not always indicate a low oil level. In fact, there are many more reasons.
10 reasons why the oil pressure light is on
Within the framework of this material, the 10 most common reasons for the operation of the oil pressure lamp are considered:
- Low oil level.
- Low viscosity oil.
- Fuel or coolant entering the engine lubrication system.
- Dirty oil filter.
- Incorrectly selected filter.
- Dirty oil pickup screen.
- Blockage of oil channels.
- Defective relief valve.
- Defective oil pressure sensor.
- Defective oil pump.
Let's analyze them according to the principle: why the oil pressure lamp is on, what the consequences can be and what to do.
Reason 1. Low oil level
The oil is taken by the pump from the sump through the oil receiver. Due to the low level, he "does not reach" him. As a result, the oil pump simply has nothing to create pressure in the lubrication system. In such cases, the control lamp does not go out after starting the engine and is constantly lit during its operation. Sometimes the lamp does not burn constantly, but flashes intermittently. This is due to the fact that the oil pickup is immersed in oil from time to time when it flows over the sump due to roughness in the road.
What to do? Stop the engine. Wait a couple of minutes for the oil to drain into the pan. Check the level with a dipstick. If necessary, add oil to the required level. It is recommended to add the same oil that was originally poured into the engine. If the level drops too quickly (less than 1 liter per 10,000 km), the cause of the leak must be found and repaired.
Reason 2. Low viscosity oil
Oil pumps in internal combustion engines are designed and operate a little differently than water pumps. If the oil is too fluid, or in other words not viscous enough, the oil pump cannot pump enough oil to build up pressure. As a result, the pressure warning lamp may go out with a long delay after starting the engine and flash during operation. The result of such operation will be oil starvation, which will lead to accelerated wear of engine parts and may cause its failure.
What to do? Check the viscosity of the lubricant. This can be done using a dipstick designed to control the oil level in the engine. Remove the dipstick with the engine warmed up to operating temperature and look at the behavior of the oil. If it runs off the dipstick like water, the viscosity is too low. This happens for two reasons - the oil is selected incorrectly or its characteristics have decreased as a result of long-term operation. In any case, such oil should be replaced immediately.
Cause 3. Fuel or coolant getting into the lubrication system
Fuel and coolant have a much lower viscosity than engine oil. When any of these fluids enter the sump in large quantities, the viscosity of the oil is disturbed. The pump is not able to create sufficient pressure from such lubricant, as a result of which the indicator lamp on the instrument panel lights up or flashes.
What to do? Check the condition of the engine oil. If it has an abnormal color, contains foam and other inclusions, it is necessary to find out and eliminate the cause.
Reason 4. Dirty oil filter
Before supplying oil to the channels of the lubrication system, the pump first pumps it through the filter. The one that needs to be changed at every oil change. If the filter is used longer than it should be, or has not been changed at all when changing the oil, it is likely that it is clogged with engine wear products. As a result, the throughput of the filter element has decreased, and the pump is simply unable to pump enough oil through it to create pressure.
What to do? Replace filter. Do not ignore this procedure at every engine oil change.
Reason 5. Incorrectly selected filter
It often happens that when changing the oil, a cheap or first oil filter is bought instead of the original or recommended by the engine manufacturer. With this approach, there is every chance to install a filter with insufficient bandwidth. The result is a situation similar to that described above. The oil pump cannot pump enough oil through such a filter. The control lamp of pressure on the instrument panel burns constantly or blinks intermittently.
What to do? Find out the marking of the oil filter installed on the engine and find out their compatibility. If the filter does not meet the manufacturer's recommendations, immediately replace it with a suitable one.
Reason 6. Dirty oil receiver mesh
Deposits on the oil receiver mesh reduce its throughput, due to which the pump is not able to create normal pressure in the system. The control lamp goes out after starting the engine with a long delay, does not go out at all, or flashes intermittently. Deposits on the oil pickup screen most often accumulate when the engine oil is systematically changed too infrequently. For most engines, this should be done at least every 10,000 km or once a year.
What to do? If there is a suspicion that the oil receiver mesh is contaminated with deposits, it is necessary to remove the sump and clean it. In not very advanced cases, additives that are designed to flush the engine before changing the oil help to get rid of plaque. The components included in their composition liquefy solid deposits, after which they accumulate in the form of sediment at the bottom of the pan. I must say that such a solution only temporarily eliminates the problem. It is possible that after a while the pressure lamp will light up again for the same reason.
Reason 7. Blockage of oil channels
That part of the engine lubrication system, which functions due to the pressure created by the pump, consists of numerous channels and holes. Their cross-section is rather small and they are easily clogged with wear products and solid particles formed from oil that is rarely changed. As a result, the pump works normally, creating high pressure, but the lubricant does not reach the rubbing parts, since the path for it is blocked by deposits.
What to do? Change engine oil in a timely manner. In the event of signs of contamination of the lubrication system, it is necessary to completely disassemble and clean the engine. As in the previous case, the use of engine flush additives sometimes helps. But no one can guarantee you a positive result.
Reason 8. Defective pressure reducing valve
The pressure reducing valve is a mechanical device designed to bleed engine oil when the upper pressure threshold in the system is reached. This is necessary so that the lubricant is not squeezed out of the engine through the sealing elements. The failure of the pressure reducing valve is that it is stuck in the open position. That is, it constantly bleeds engine oil into the sump, which is why the pump cannot create normal pressure.
What to do? It is necessary to remove the pressure reducing valve and check its condition. In case of breakage, replace the part with a new one.
Reason 9. Faulty oil pressure sensor
In case of damage to the membrane or other elements of the sensor, it is constantly in a closed state. This leads to the fact that the pressure in the lubrication system is normal, but the control lamp on the dashboard does not go out and is constantly on. Sometimes the oil pressure sensor is destroyed due to the systematic operation of an unheated engine. There may also be contamination of the hole through which oil enters the sensor and acts on the membrane.
What to do? Remove the pressure sensor and check its operation. Without special equipment, it can be called a multimeter. If it passes current without any pressure, then it is jammed. Please note that not all motors are equipped with normally open sensors. Therefore, before checking, it is necessary to clarify what type of sensor is used on the engine of your car. The defective sensor must be replaced with a new one.
Reason 10. Faulty oil pump
In internal combustion engines, oil pumps are used with a very simple and extremely reliable device. With proper operation, this unit operates in "paradise conditions" - constantly lubricated. Therefore, it wears out and fails quite rarely. However, oil pump failure is not ruled out. In such cases, there is no pressure in the system at all. Even despite the fact that the oil level in the pan is at the maximum mark.
What to do? Remove the oil pump from the engine and inspect it. If critical wear is detected, the assembly must be replaced.
Causes of the engine oil pressure lamp
Low oil level
The oil intake does not reach the oil in the sump, which is why the pump has nothing to create pressure in the lubrication system
Stop the engine, wait a couple of minutes, check the engine oil level and add it if necessary
Oil of the wrong viscosity
The pump is not able to pump overly fluid oil, due to which the pressure in the lubrication system does not rise
Assess the viscosity of the oil visually, replace if necessary with one in accordance with the recommendations of the engine manufacturer
Other liquids in oil
If antifreeze or fuel enters the lubrication system, its viscosity is significantly reduced, due to which the pump cannot create pressure
Check the color, transparency and consistency of the oil, if necessary, eliminate the cause of mixing with another liquid, then replace the oil with fresh
Dirty oil filter
A clogged oil filter creates excessive resistance to the oil pumped by the pump, which prevents the pressure in the lubrication system from increasing
If the oil has been changed for a long time, or the filter was not changed during the last change, it must be replaced immediately
A non-original filter, smaller in size, a cheap analogue - may have insufficient throughput, which creates resistance to the oil, and the pump cannot create pressure
Set the compatibility of the oil filter with the engine model, if necessary, replace it with a suitable option
Clogged oil receiver
The pump sucks oil from the engine sump through an oil receiver with a mesh, which, in a clogged state, does not allow taking in a sufficient amount of lubricant to create a working pressure
Drain the engine oil, remove the sump from the engine and evaluate the condition of the oil receiver screen, if necessary, wash the filter element or replace it with a new one
Blockage in the lubrication system
Dirt has accumulated in the channels with a small cross section, which prevents the normal circulation of oil through the system, due to which the pump cannot create normal pressure
Flush the lubrication system with a special additive, if it doesn’t help, completely disassemble the engine and fix the problem, then change the oil and filter in a timely manner
Pressure reducing valve
A faulty pressure reducing valve bleeds all the oil into the sump, due to which the pump cannot create working pressure in the lubrication system
Remove and check the pressure reducing valve, if necessary, replace with a new one.
Oil pressure sensor
A faulty oil pressure sensor causes the instrument panel warning light to stay on, regardless of actual system pressure
Remove the sensor and check its performance with a multimeter, if necessary, replace with a new one
Critical wear of the oil pump causes low pressure in the system, and in the event of a node failure, the pressure in the system is zero
Remove the oil pump, carry out diagnostics, assess the condition, replace worn parts or the entire assembly
Checking the oil pressure lamp
Nothing needs to be done to make sure that the engine oil pressure monitoring system is working. The corresponding lamp with the image of an oil can on the instrument panel should light up every time the ignition is turned on. A moment after the successful start of the engine, the lamp should go out.
If the lamp does not light when the ignition is on and the engine is not running, this indicates a malfunction of the oil pressure control system. In such cases, starting and operating the engine is strictly prohibited. The first step is to check the lamp itself. To do this, it must be removed from the dashboard and checked by connecting directly to the battery or other 12 V power source.
If the lamp is working, but does not light up in the dashboard when the ignition is turned on, it is necessary to check the pressure sensor installed on the engine. If it is also working, then the problem is in the wires that connect these elements and are connected to the battery.
Note. Before looking for the reason why the oil pressure lamp does not light when the ignition is on, make sure that there is power in the on-board network. This is evidenced by the battery charge control lamp on the dashboard, which should work synchronously with the oil pressure lamp — light up when the ignition is turned on, and go out after the engine has been successfully started.
The engine oil pressure lamp is the most important indicator of the condition of an automobile engine. If it does not go out after a successful start, or if it lights up on the way, stop the engine immediately and find out the cause of the low pressure. Each time the ignition is turned on, this lamp should be checked — if it does not light up, it is not worth starting the engine until the cause is clarified and eliminated.