What Causes Blow by in A Diesel Engine?

A blow-by in a diesel engine can affect the generator by making a hissing noise, incomplete combustion, oil contamination, and damaging the engine performance. To understand what causes a blow-by in a diesel engine, you need to look out for symptoms such as white smoke, misfiring, increased oil consumption, and runaway engines.

Although diesel generators can provide more power due to higher energy density, solar generators like Jackery Solar Generator stand out due to their reliability, affordability, and eco-friendliness. Solar generators use renewable energy to power your devices and do not cause wear and tear.

Key Takeaways

• Almost all diesel engines can cause blow-by, mainly due to piston rings.
• An engine consumes more fuel than usual in case of a blow-by.
• When pressure is maximized, a blow-by occurs during a power stroke.
• Engine blow-by can occur in diesel and gas engines.

What Is Blow By in A Diesel Engine?

Blow-by is the unwanted gas leakage, such as from a piston or sealing rings, and it can affect all diesel engines. It occurs when too much pressure in the combustion chamber and the gas leaks into the crankcase.

Blow-by in a diesel engine can lead to several problems, including poor engine performance and increased emissions. It occurs when combustion gas escapes the piston rings into the crankcase and exits the system. This can cause oil sludge formation, which consumes the engine oil. A blow-by reduces the engine's efficiency by increasing its wear and tear and can cause premature failure.

What Causes A Blow- By in A Diesel Engine?

Blow-by happens when internal combustion forces air, fuel, or moisture past the piston rings into the crankcase. There might be a case when your engine piston rings are incorrectly fitted and cannot contain the pressure produced from the combustion. It will then leak the contaminants. Moreover, any soot or deposit left from incomplete combustion will gather on the rings and worsen the engine blow-by. Here are some additional reasons that cause a blow-by in diesel engines:

Damaged Pistons

Damaged pistons are one of the major causes behind a diesel engine blow-by. These are made up of soft metals like aluminum. When heated, it can expand faster than steel, and when the piston undergoes extensive use, it wears out and becomes smaller. The grit builds up in the combustion chamber, which does some groove carving of the piston. The compressed fuel or air escapes in the crankcase from these grooves and causes the engine to blow by.

Defective Piston Rings

When the rings are scraped continuously back and forth in the cylinder, they get damaged, and their property to seal fails. This causes difficulty for the worn piston rings in maintaining a close seal. When the internal combustion is incomplete, it deposits soot, sludge, or oil on the piston rings, worsening the seal failure. If the seal is not there or it is damaged, the engine contaminants can leave the crankcase and into the air and cause the engine to blow by.

Worn Cylinder Walls

As the diesel engine ages, the cylinder walls wear down due to piston and ring scraping. This expands the bore of the cylinder over time and eventually forms a slope or space between the piston and cylinder. Compressed gases flow around the piston as the distance between the piston and cylinder increases, eventually causing engine blow-by.

Clogged Crankcase Ventilation

The crankcase ventilation system can build up the pressure if it is clogged, which leads to a blow-by. If the engine is excessively heated, it can cause the parts to expand and wrap. Moreover, with time, the engine components wear down naturally and can cause more blow-by.

Scratching and Scouring

Another area in the engine that is susceptible to damage, as any other component, is the core of your engine. There are many causes of the damage, including dirt and debris in the cylinder, oil with carbon, and leaking injectors. If found damaged, the cylinder walls, pistons, and rings may create ways for combustion gasses to leak.

How Does A Blow By Effect The Diesel Engine?

Your engine can show several signs of a blow-by. If you know what to watch out for and catch the problems early, you can avoid costly repairs and downtime. A blow-by can affect the engine by causing sputtering noises, increased incomplete combustion, and oil contamination that causes leaking. Ultimately, blow-by affects the crucial engine processes by showing various symptoms, and each symptom has its own effect.

Smoke: White or black smoke is an evident sign of engine blow-by. White smoke comes from the aperture on the valve cover or an oil-fill tube. It indicates that a blow-by has occurred, and the engine needs immediate attention.

Misfiring: When a blow-by gets into critical engine functions, it becomes challenging for the generator to start. Even if the generator starts, it might be challenging to keep running. If there is a loss of compression in the chamber, there might be a possibility that the diesel engine may exhibit idling and misfiring. When the combustion gasses escape early from the combustion chamber, this causes the engine to misfire.

Increased Oil Consumption: If oil or fuel leaks into the crankcase, it might be because the engine consumes more fuel than usual. In this case, a blow-by could contaminate the crankcase oil. Constantly monitor your oil levels to ensure your engine will not seize.

Exhaust Smoke: Compared to white smoke, excessive smoke caused by blow-by is often thick and discolored.

Poor Engine Performance: A cylinder cannot contain much pressure when it leaks. When the combustion gases escape the piston rings due to expansion, they do not let the engine produce a considerable output during the power stroke. This results in a reduction in horsepower and slowing engine acceleration.

Runaway Engines: At times, the engine can be at risk of speeding out of control due to a blow-by. Another indication is the formation of an oil film around the tube. When unburned gasoline is present due to an engine blow, it contaminates the oil and gets into the crankcase. If the blow increases, the diesel may escape if the mixture reaches the chamber.

Soot Buildup: Due to incomplete combustion caused by blow-by, soot formation takes solace in the cylinder walls. If there is excessive soot, consider changing your oil.

Loud Noises: When an engine experiences a blow-by, it makes a louder noise and pollutes toxic fumes from the vents. A loud noise clearly indicates a blow-by, followed by the release of exhaust clouds.

How to Identify & Test A Blow By in The Diesel Engine?

Some symptoms and signs indicate a surefire way to know if the diesel has a blow-by. You can check your engine oil; if it is thick, dark, and contaminated, it is most likely that a blow-by occurred. Next, There will be an increase in the amount of smoke, either black or white, depending on how severe the blowby is. Another sign is a loud sound from the engine caused by the gasses passing through. Although the symptoms can give you a general idea of a blow-by, there are some steps or tests through which you can identify the blow-by in a diesel engine:

Leak Down Test

A leakdown test measures the percentage of blow-by caused in the engine. For this, you need a gauge testing tool to measure how much pressure goes into the cylinder and how much is escaping. The percentage loss indicates the overall condition of the combustion cylinder and engine. If you do not have a dual-gauge testing tool, you can consult a service mechanic to check the cylinder. The test will take around two hours to complete.  

Oil Filler Cap Test

In this method, you must remove the oil filler cap while the engine runs. If smoke is coming out, it indicates excessive blow-by.

Dipstick Test

This is similar to the oil filler cap, and here, you need to remove the dipstick while the engine is running. Similarly, if you see gas or smoke emissions, it could indicate a blow-by.

Crankcase Pressure Test

You can measure the crankcase pressure with the help of a manometer. If the reading is higher than normal, it can indicate a blow-by.

While a blow-by can cause serious damage, it is still possible to fix it. With proper maintenance, you can reduce or eliminate a blow-by. Keep inspecting your engine thoroughly and checking the engine components in a timely manner. Replace any broken parts if needed, and use good-quality motor oil at recommended intervals.

How to Prevent A Blow By in The Diesel Engine?

As of now, a blow-by can have several underlying causes. But, many preventive measures can be taken to reduce or eliminate it. Proper engine maintenance, regularly changing the oil and filter, and checking for blockages are some common steps that can be taken to prevent a blow-by. Here are some additional preventive measures that could be taken to avoid diesel engine blow-by:

Maintain The Piston Rings

The first step is to ensure that your combustion cylinder is working correctly. To do that, you need to maintain the piston rings. The piston rings should be intact, defective, and of the correct size. High-performance pistons should seal adequately.

Use Oil Treatments

Regular oil treatments can keep your piston rings lubricated and prevent them from sticking to the wall chamber. Some also believe that piston rings do not work and are not a cure-all, but if you use them regularly, they can reduce the blow-by.

Install Oil Separator

An oil separator helps to remove oil from combustion gases, reducing pressure in the crankcase. If the engine is old, a vent tube can also reduce combustion chamber pressure.

Replace ICP Sensor

A damaged injection control pressure valve can cause rough idling in the engine. This valve regulates the oil pressure coming from the oil pump. A diagnostic tool checks the IPR valve when its duty cycle value is set to minimum and maximum. If the oil pressure doesn’t change, it may indicate a broken valve.

Preventive Maintenance

Regular engine maintenance is another key factor in reducing the chance of engine blow-by. Changing the engine oil is important as it helps to remove carbon buildup, which can destroy the metals. You can use detergents or oil treatments to dissolve solids and carbon buildup into liquid form.

Proper engine maintenance is vital to reducing the chances of engine blow-by. Frequently changing the engine’s oil will help remove any solid carbon buildup known to erode metals. Adding treatments and detergents to the fuel and oil will help dissolve solids and buildup into liquid form, making them easier to remove.

Since engine blow-by is a common occurrence, all small and large engines can have one. New engines can have minor levels of blow-by due to the inefficiency of piston rings.

Does A Diesel Generator Have Blow By?

When combustion gasses are leaked into the crankcase, it causes blow-by in diesel engines. So, both diesel and gas generators can have a blow-by due to component issues. Here is a comparison of diesel, gas, and solar generators:

Diesel Generator

Diesel fuel has a longer shelf life and provides more power to a diesel generator for its size and weight due to higher energy density. Diesel generators produce higher power outputs of 3000 - 10000 watts, mainly for commercial uses. Since it has a large engine and alternator, they come in larger sizes and can run more heavy appliances due to high power. The minimum weight of a portable diesel generator can be around 60 kg and can go up to 500 kilograms of installation generators. Diesel generators are louder than gas generators, causing a noise of around 70-80 dB.

Working Principle

Diesel generators produce electricity by burning diesel fuel and using a combination of electric and diesel generators. Diesel generators transform chemical energy into mechanical energy through combustion. This mechanical energy causes crank rotation to produce electricity, and when the wire is moved through a magnetic field, electric charges are induced in it.

In the electric generator, a magnetic field is produced by polarized magnets. After wounding around the crankshaft multiple times, a wire is placed between these magnets and in the magnetic field. Once the crankshaft is rotated by the diesel engine, the wires start moving throughout the magnetic field and induce electric charges.

Pros

Diesel fuel has higher energy density and can power critical loads during an outage. Unlike gas generators, diesel generators require fewer components to start, so you need not worry about changing or rebuilding any component. Even in extreme weather conditions, diesel generators hold up through wear and tear. Unlike gasoline, diesel has a lower ignition risk and can run for longer durations.

Cons

Diesel generators are the most expensive and loudest type of portable generator. They demand expensive fuel costs and prolonged maintenance. Diesel generators intensely impact pollution as they emit Carbon dioxide, carbon monoxide, nitrates, and particulate matter.

Natural Gas Generator

Gas generators run on liquefied petroleum gas (LPG) instead of gasoline or diesel. They tend to be quieter than diesel generators. For various residential and industrial uses, gas generators produce power outputs ranging from 5000 to 100,000 watts. They are larger in size due to a larger natural gas generator and turbine. Depending on size, they can be either portable or installed permanently, weighing around 60-80 lbs.

Working Principle

Natural gas generators use propane or natural gas to harness mechanical energy and create electricity. In the first step, the combustion engine injects fuel and air into the combustion chamber. The piston compresses the mixture, and the spark plug ignites the fuel.

This spark creates an explosion, which turns the generator into mechanical energy. Due to ignition, the gasses expand and push the piston down to turn on the crankshaft. The crankshaft spins the rotor, which enables the stator wires to conduct electricity and power appliances.

Pros

Unlike diesel generators, natural gas generators are odorless. You do not need to refill a natural gas generator, and it is suited for wet conditions.

Cons

Natural gas's explosive nature can cause a fire hazard if the pipeline bursts. Natural disasters like earthquakes can disturb natural gas supplies. Natural gas generators are expensive upfront and maintainable. Although natural gas is not renewable and causes pollution.

Solar Generator

Solar generators come with solar panels and power stations to charge the battery during the daytime. These are eco-friendly but might have lower inputs than gas generators. The power output can range from 100-2000 watts depending on the size and solar panels used. Solar generators are enough for charging big and small appliances. Running times depend upon the power of the running device and the capacity of the solar generator. Due to solar panels and lithium batteries, the upfront cost can be higher than that of gas generators. Solar generators are very quiet and have noise levels below 55 dB.

Working Principle

A solar generator combines solar panels and a power station. When placed out during sunlight, the solar panels trap sun energy. A battery stores this energy and keeps it for later use. The in-built inverter then converts direct current (DC) into alternating current (AC) to charge the devices. A charge controller is needed to control the charge that gets into the battery directly from the sun.

Pros

Solar generators cannot cause wear and tear as they have no moving parts and are not easily damaged otherwise. They are environmentally friendly as they do not emit toxic fumes or greenhouse gases and reduce the dependency on fossil fuels. Solar generators are reliable as long as sunlight is available, and you can store energy in the battery for future use. Solar generators can regulate charging and have AC outlets and DC ports compared to other generators.

Cons

Acquiring and setting up a solar generator can be expensive. On days when there is no sunlight, you might have to compromise on your power supply.