Why is there no compression in one cylinder? Check, measure and replace

2024 Author: Henry Conors | [email protected]. Last modified: 2024-02-12 02:40

The pressure in the cylinders of an internal combustion engine is one of the main parameters of its normal operation. With low compression, the engine will run unstable. Lack of pressure in one or more cylinders can cause serious problems in the future. Let's look at the situation when there is no compression in one cylinder.

Does the lack of pressure always indicate a malfunction?

Before considering the main causes and signs of this phenomenon, let's figure out how this parameter affects the overall performance of the engine. If the pressure in the ICE lubrication system is below the norm calculated by the manufacturer, then practice shows that the ICE components will be excessively worn out. But if we talk about compression, then this is not always the case. When the rings on the pistons are mated with the cylinders, the lubricant is very important - it collects on the walls of the cylinder. Due to the oil, the gaps between the rings and cylinders are sealed.

When not the entire volume of the combustible mixture burns in the cylinders, this will lead to high fuel consumption. If one or more spark plugs fail, the gasoline entering the combustion chamber will wash oil off the cylinder walls. This fuel is an excellent solvent. If there is no lubrication in the cylinder, if there is no pressure in the lubrication system, then the oil will no longer be able to sufficiently seal the gaps in the cylinder. Therefore, air under high pressure and gases formed during the combustion of the air-fuel mixture will enter the crankcase. This will lead to the fact that in a 4-, 6-, and also an 8-cylinder engine, the compression will drop sharply, and then drop altogether.

If the compression is even higher than necessary, this will also cause increased oil consumption. Due to the high oil compression, ring wear will be more intense. The gaps that inevitably form during the operation of the engine are perfectly sealed with grease, which is plentiful. In this case, an urgent repair is needed. However, in fact, compression will not show this problem.

Signs of a problem or lack thereof

If there is no compression in one or several cylinders, then this can be determined by the following symptoms:

• Difficulty starting the engine will report low pressure. The motorist, when trying to start, will turn the flywheel with the starter for much longer than usual. If the pressure disappears completely, then starting will become almost impossible.
• An engine with low compression in one of the cylinders will triple, work withless stability. Since there is no compression in one cylinder, the rpm will be unstable even at idle. This will also be displayed on the acceleration dynamics.
• Of course, this engine will have increased fuel consumption. It is quite difficult to determine this symptom for those who do not follow this indicator. But for those who know the consumption for a certain mileage, the increase in engine appetite will be immediately noticeable.
• There will definitely be malfunctions in the operation of the combustion chambers. When driving uphill, hydraulic lifters may begin to knock. This will be especially clearly visible and audible when driving at low speeds.
• In diesel power units, it is possible to determine that there is no compression in one cylinder by characteristic pops.
• Sometimes pressure can build up in the lines where the coolant circulates. Antifreeze due to low compression will be squeezed out from under the gaskets, from under the nozzles and other seals.
• With poor compression (if it is due to a broken cylinder head gasket), the tightness of the system is violated. If you open the hood, you will see exhaust gases passing through the gap in the gasket. This malfunction leads to the occurrence of rings on the pistons, which will contribute to increased oil and fuel consumption. In some cars, this symptom may be accompanied by an increase in power and the formation of white smoke from the exhaust pipe.

How long can an engine run?

Low or no compression in an engine is a common problem faced bymotorists. If the pressure has decreased slightly, then the engine may well be operated for a long time. However, too low pressure can occur due to severe overheating of the internal combustion engine. Below we will try to find out why there is no compression in one cylinder. Consider mechanical and non-mechanical causes.

Non-mechanical damage

First, it is worth dealing with the non-mechanical causes that led to the lack of compression in an automobile internal combustion engine.

This includes various mistakes that a mechanic could make during the repair and assembly of the unit. If the motorist on his own or the specialists at the service station have incorrectly set the timing marks or the valve timing (and this often happens due to inattention), then the valves will not close when the principle of operation of the internal combustion engine requires it. During the compression stroke, the valves do not have time to close completely, because the phases are knocked down. As a result, some of the air will simply come out.

Sometimes non-mechanical compression problems can be caused by coking on the piston rings. This problem can later lead to sticking of the valves in the grooves. Gases will pass easily as there are no seals.

In this case, if there is no compression in the 1st cylinder or any other, the oil scraper ring on the piston will not be able to perform its function, and the lubricant will also not be able to fill the gaps - it will be washed off the cylinder wall with unburned gasoline.

Mechanicalproblems

If a 4-cylinder or larger power unit works, but there is no compression, then the reasons may be in mechanics. Compression suddenly disappears for one of the following reasons:

• Exhaust valves are the most commonly damaged. Cracks can often be observed on the valve. This is due to the natural wear of the engine. The valve does not fit snugly against the seat in the cylinder head. That's why there is no compression in cylinder 2.
• Also one of the reasons is valve seat wear. The decrease or lack of compression is due to mechanical damage. Often the seat is pressed through.
• A popular cause is a burnt gasket between the engine block and the head. Experts are sure that this is an inevitable situation, which appears due to the high mileage of the car. A little less often, the cause of burnout of the gasket is the ingress of dirt onto the plane. This problem is encountered when the engine is operated at elevated temperatures for a long time. The cylinder head cracks, the block is deformed.
• Scoring in the combustion chambers can also be attributed to the mechanical reasons for low compression. There are many reasons for the formation of scuffs, but the most common is overheating. If a piston ring is broken inside the cylinder, this leads to scuffing. Damage to CPG parts also leads to a decrease in compression. For example, interring jumpers on pistons often break.
• If the timing belt breaks, there will be no pressure in all cylinders and the engine will not start.
• Inlet valves fail. Cracks form on the pistons or on the wallscylinders. Soot appears on the valve seals and on the rings. All this helps to reduce compression.

A sharp drop in compression can lead to very serious malfunctions in the operation of the power unit. If there is no pressure in one of the cylinders, then a diagnosis must be made. Next, consider how to check the compression in the cylinders.

Measurement rules

The engine immediately before the measurements is spun by the starter to the maximum possible speed. To do this, open the hood and remove the wires from the spark plugs. The candles themselves are unscrewed. This will remove the resistance to the rotation of the flywheel by the starter. Before measuring, the engine must be warmed up. Before measurements, the fuel supply is turned off so that gasoline does not wash the oil off the cylinder walls. The battery must be charged in order for the starter motor to turn the flywheel properly.

Preparing the tool

To check the compression in the cylinders, you need a compression gauge. This is a pressure gauge with an extension cord and an adapter for screwing into candle wells. Compression gauges may vary. They are different for gasoline and diesel engines.

Open the hood, disconnect the spark plug wires, remove the spark plugs. Then prepare the compression gauge for work. Adapters of appropriate sizes are connected to the device and the adapter is screwed into the candle socket. Then the driver sits in his seat, fully depresses the gas pedal and turns the engine over with the starter. After rotation, you need to lookto the measurement result. You should first find out in the instructions for the car what the compression in the cylinder should be - for most gasoline engines, the value should be around 12. The check is performed in each cylinder.

Oil Compression

If there is no pressure, then this is either a problem with the cylinder head, or a malfunction or natural wear of the CPG. To determine which of these two factors is the cause, you need to add oil to the combustion chambers.

If there is no compression in the 3rd cylinder or in any other, then a little oil is poured into the cylinder before measuring with a compression gauge. Enough 50 grams. If the compression increased after the bay, then the problem is in the rings. If the pressure has not changed, then the problem is in the cylinder head. Both in the first and in the second case, you will need to disassemble the engine for repair.

How to increase compression?

If there is no compression in the 4th cylinder, you can try to raise it. To do this, decoke the rings. You can use dimexide, "Laurel" and other products available on the market. But this is not a panacea, and it will not allow to avoid repair. This measure is only temporary.

Conclusion

So, we have examined why compression is lost in a car engine. As you can see, there are many reasons for this phenomenon. But in any case, do not delay the repair.