The appearance of the smell of fuel in engine oil or a visual change in its level is an alarm signal, the neglect of which can lead to major repairs to the engine. carburetor This problem is much more common than in injection systems, because of the design of the mixing system, and the fluid that flows into the crankcase doesn't just dilute the lubricant, it changes its physical properties dramatically, turning the protective layer into an aggressive environment.
Many motorists notice something wrong only when the oil level rises above the maximum mark on the probe, and the unit itself begins to work intermittently. ICE And in these conditions, the energy of the mixture is very high, because the lubricating capacity of the mixture drops to almost zero, and if you hear a characteristic smell or notice a smoky exhaust, you have to stop operating immediately and make a diagnosis.
In this article, we will take a closer look at the mechanics of the process, explain how fuel travels from carburetor to oil pallet, and provide a clear algorithm for correcting the malfunction. Understanding the physics of the processes will help you avoid costly repair errors. Critically, operating an engine with oil levels above the MAX mark can lead to extrusion of the glands and hydraulic shock.
Fuel penetration mechanism into the crankcase
To understand how gasoline ends up in oil, you need to look at the path of the fuel-air mixture. Solex or Ozonmixing occurs by dilution in the intake manifold. fuel-mix does not burn completely or does not enter the cylinders at the right moment, it flows downwards by gravity or under pressure, bypassing the combustion chamber.
The main channel of penetration is the gaps between the piston rings and the walls of the cylinders. During normal operation of the engine, some gases still break into the crankcase, but the ventilation system (Ventilation system)PCVHowever, when liquid gasoline enters the crankcase in large volumes, the ventilation system fails and the fuel settles in the pallet, mixing with the lubricant.
This process can be instantaneous (with a sharp failure of the nodes) and gradual, accumulating over hundreds of kilometers of run, in the latter case, the driver may not notice changes in the operation of the engine until the viscosity of the oil drops to critical values, which is why regular testing with probes is a mandatory procedure for owners of carburetor equipment.
Defects of the carburetor needle valve
One of the most common causes of fuel overflow is loss of leakiness. needle-valveThis is the junction that's responsible for blocking the flow of gasoline from the float chamber when it reaches a certain level, and if the needle cone is worn out or there's a little bit of debris between the needle and the saddle, the valve stops holding pressure.
As a result, gasoline continues to flow into the float chamber even after the float has risen, excess fuel through the idling system or the main jelly is actively sucked into the intake manifold, the engine runs on a re-enriched mixture, some of which does not have time to burn and flows down the walls of the cylinders, into the intake manifold. crankcase.
Often the problem is compounded by misadjustment of the fuel level in the float chamber, where if the float tongue is bent too much or the float itself is leaky and drowned, the gasoline level rises above the permissible level, which creates an excess pressure that pushes fuel through closed valves even on a silenced engine.
⚠️ If after a long parking the engine is difficult to start, and from the exhaust pipe goes black smoke - this is a sure sign that the candles "throw" gasoline due to a malfunction of the needle valve.
To diagnose, you have to remove the top cover of the carburetor and flip it over. When you blow the fuel supply plug, the needle must block the hole. If the air is free, the knot needs cleaning or replacement. Remember that the rubber needle seals blister over time and lose elasticity.
Problems with the fuel pump and diaphragm
Many classic cars and motorcycles use a mechanical gas pump driven by an eccentric on a camshaft, and the design of these pumps often involves two diaphragms and a drainage hole between them. If one of the diaphragms breaks, the gasoline starts flowing out of the mainline, but through a drainage hole right into the main. crankcase.
This is perhaps the most dangerous scenario, because the fuel flows into the oil by gravity and constantly, even when the engine is turned off. During the night, a significant amount of gasoline can be in the crankcase, which, when you try to start, will lead to a hydraulic shock or instantaneous destruction of the oil film at start.
If the drainage drips or leaks gasoline - the diagnosis is unequivocal. It requires immediate replacement of the remplekts of the gas pump or the entire assembly. Operating equipment with such a malfunction is strictly prohibited, since the risk of fire when heating the oil also increases many times.
Symptoms of rupture of the diaphragm of the benson pump
The sharp smell of gasoline in the engine compartment and cabin, which is enhanced after parking. The level of oil on the probe increases for no apparent reason (oil was not consumed). The engine can become deaf at idle speeds due to air suction through the rupture, if the design provides such a path, but more often the gasoline is simply poured into the crankcase.
And there are electric gas pumps in the tank or under the bottom, and although they are less likely to flow directly into the engine, a failure in the pressure regulator or the back valve can create overpressure in the mainline, and the carburetor can't digest that pressure, doesn't hold the needle, and there's a classic overflow with all the consequences.
Impact of the ignition system and candle condition
It is not always the fault of the excess fuel; sometimes the problem is that the normal amount of the mixture simply does not burn. Ignition system If the spark is weak, the timing is knocked down, or the candles have too much clearance, the fuel does not ignite efficiently.
The unburned condensate mixture settles on the cold walls of the cylinders and drains through the piston rings into the oil, especially on frequent short-distance trips when the engine does not have time to reach operating temperature, in which conditions carburetor engines are prone to “oil starvation” due to liquefaction.
Notice the color of the candles, black, velvety soda indicates a rich mixture, and oily plaque indicates problems with oil rings or oil entering the combustion chamber, which indirectly affects the overall balance of the engine. Regular replacement of candles and checking of high-voltage wires is a basic requirement for motor health.
- 🔥 Check the angle of ignition advance with a strobescope or by ear (by the method of "spark" for experienced).
- 🔌 Inspect the ignition distributor cover for breaks and cracks, especially in wet weather.
- ⚙️ Make sure that the vacuum corrector ahead of ignition works and the membrane is intact in it.
- 💡 Replace spark plugs if the mileage on them exceeded 15-20 thousand kilometers.
Diagnosis and verification methods
Before you start dismantling the carburetor, you need to conduct a competent diagnosis, so as not to change the working parts. First of all, assess the condition of the oil visually and smell. Put oil on a hot surface (for example, on the exhaust manifold, with caution): if it flashes or smokes heavily with a pungent smell, there is gasoline there.
Next, you should check the compression. Low compression in one or more cylinders may indicate the occurrence of rings, which contributes to the fuel getting down. It is also worth checking the valves: if the valve is not tightly attached to the seat, the fuel will go to the exhaust system or, conversely, suck back.
☑️ Diagnosis of gasoline in the oil
The precise adjustment of the carburetor often requires readings of the mixture with a gas analyzer, but in garage conditions you can focus on the color of the candle electrodes and the behavior of the engine. It is important to conduct the check consistently, eliminating one after another possible causes.
| A symptom. | Probable cause | Method of verification |
|---|---|---|
| Oil smells like gasoline, level rises | Unsealed needle valve | Remove the top of the carburetor lid, blow the fitting |
| Gasoline leaks from pump drainage | Rupture of the benson pump diaphragm | Visual inspection with the working or silenced engine |
| Black smoke, candles, soak. | Re-enriched mixture | Analysis of candle color, checking the fuel level in the float chamber |
| Engine troite, oil liquid | Ignition skips | Checking sparks, VB wires, compression |
Effects of operation and oil replacement
Ignoring the problem leads to disastrous results. Motor oilThe oil film on the rubbing vapors (knee, camshaft, piston group) becomes too thin and breaks, causing dry friction, overheating and rapid wear of parts, known as "turning the liners."
In addition, gasoline in the oil accelerates the oxidation of the lubricant, forming slags and lacquer deposits that clog the oil channels, which can lead to oil starvation even if there is enough fluid in the pallet, repairing it will cost several times more than replacing the carburetor's spear remix in a timely manner.
If you find gasoline in the oil, it needs to be replaced immediately, even if you just changed it. Washing the engine with a special wash oil is mandatory, since part of the fuel mixture is left in the hidden cavities and on the parts. Once the oil is changed and the cause of the malfunction is eliminated, the first replacement interval should be reduced by half.
⚠️ Warning: Never try to burn off oil by heating up the engine at high speeds, which will only cause local overheating and possible ignition of vapors in the crankcase, which can cause an explosion.
After changing the oil and filter, let the engine run for 5-10 minutes at idle speeds, then check the level again. Often, fresh oil absorbs the remaining gasoline from hard-to-reach places, and the level can rise again.
Carburetor regulation and prevention
The proper adjustment of the carburetor is the key to clean engine operation, you need to adjust the quality and quantity of the mixture at idle, and check the accelerator pump, the jet from the nozzle of the accelerator pump should be powerful and straight, not touch the wall of the diffuser.
Prevention involves putting a high-quality, fine-cleaning fuel filter in front of the carburetor, and it's the dirt and rust from the tank that most often cause the needle valve to jam, and changing the filter regularly without waiting for complete patency loss.
Use only the fuel of proven gas stations. Low-octane gasoline with impurities of alcohol or water can cause corrosion of brass parts of the carburetor and the destruction of rubber seals, which will eventually lead to a violation of the tightness of the system.
The main reason for getting gasoline into oil on a carburetor is leaky shut-off needle or rupture of the diaphragm of the gas pump. Timely replacement of filters and remixes is cheaper than overhauling the engine.
Regularly conduct a visual inspection of the underhood space for leakage. Watch the exhaust color and stability of idling speeds. Any deviation from the norm should be the reason for a more detailed check. Careful attitude to the power system of the engine will extend its life for many years.
Can I drive if there is gasoline in the oil?
Not recommended, even a small amount of fuel reduces the lubricating capacity of the oil by 30-40%, long-term operation will lead to accelerated wear of the crankshaft liners and piston group, you can get to the service, but avoid high speeds and loads.
How quickly will the oil evaporate from the oil itself?
Gasoline does not evaporate from oil under normal operating conditions, especially if the engine is running in an urban cycle with frequent short trips. The oil temperature (90-100 ° C) is not enough to quickly boil large volumes of fuel. It requires long-term engine operation to hot or change oil.
Does the quality of gasoline affect this problem?
Yes, indirectly. Bad gasoline contains more impurities and resins, which more quickly contaminate the needle valve and jelly carburetor, which leads to leakage and calibration, which causes a fuel overflow.
Do I need to wash the engine if the gasoline gets into the oil?
Yes, flushing is mandatory. Gasoline dissolves additives in the oil and leaves a lacquer coating. The flushing oil will help remove the residues of the fuel mixture from the channels and from the surfaces of parts before pouring fresh lubricant.