It is important that you stay on top of vehicle maintenance, which means you need to be able to spot issues like low engine compression and know what to do about them.
Sometimes, you might be missing certain pieces of equipment that would make it easier to monitor the engine compression, but this doesn’t mean that you can’t check it still.
We have put together this useful guide to help you understand engine compression, how to check it, and what you can do about it.
Keep reading to find out more!
What Is Engine Compression?
Every type of engine requires the process of compression in order for it to run.
This process of compression is when air and fuel are put under a lot of pressure before the fuel is ignited in order to power the vehicle or machine.
What Is Low Engine Compression?
Low engine compression is when the fuel and air are not being put under enough pressure.
If the engine compression is too low then the fuel might struggle to ignite, which puts more pressure on the engine.
This pressure and strain can cause unnecessary wear and tear to certain parts within the engine, and stop it from running efficiently.
Signs Of Low Compression
There are several things to look out for which are warning signs of low compression in your engine.
If the timing belt or the timing chain has worn out then this could be an indication of low compression.
Another sign is wear to the cylinder wall and the piston ring, or an issue with the valve or the vale train.
You may also have a faulty gasket caused by low compression in the engine.
The easiest way to spot low compression is if the warning light is illuminated on the dashboard.
What Is High Engine Compression?
High engine compression means that the fuel and air are being put under too much pressure.
This can be very dangerous as it could cause the fuel to ignite prematurely, potentially setting fire to the engine and causing a lot of damage.
Signs Of High Compression
If your engine has high compression then you might notice a knocking type sound which is what happens then the fuel is igniting prematurely.
Bad wiring, faulty spark plugs, a cracked distributor cap, or even a weak coil can all contribute to or be caused by high compression in the engine.
How To Check Engine Compression With A Gauge
Modern cars often have a built-in computer which will constantly monitor the engine compression and immediately flag any issues. If you have an older vehicle, checking the compression of the engine can be very simple if you have a gauge.
The compression testing equipment will need to be set up and attached to the engine in place of the spark plug. You will then need to run the engine and test each cylinder individually. The gauge will show you the highest amount of pressure being generated in each cylinder. You can then compare this figure to the desired figures and see whether the compression is high, low, or just right.
How To Check Engine Compression Without A Gauge
You can check the engine compression without using a gauge, but it is more complicated. There are several steps you need to follow, and this process will also help you to diagnose the problem.
Step One – Timing Belt
The first thing you will need to do is inspect the timing belt. An issue with the timing belt can often be the cause of low compression, so it is best to have a look at it before you do anything else.
The timing belt is made out of strong rubber which is reinforced with metal. Look at the outside of the belt to see if there are any cracks in the rubber. Ideally, it should have a smooth and even surface with no large cracks and no pieces missing. Next, check the underside of the belt to see what condition the teeth are in. If any of the teeth are broken, this can cause big problems.
You can also twist the belt to see how much give it has. If you can turn it more than halfway then it could be that the rubber has stretched too far and the belt needs replacing. You should also turn the engine on and watch the timing belt to see how it is running. Do not touch the timing belt while the engine is running.
If everything looks fine with the timing belt, you can move on to Step Two.
Step Two – Cylinders
The next thing you need to do is pour oil into the cylinders. This will help to loosen the pistons in case they are stuck. This can help to fix low compression.
Step Three – Oil Cap
With the engine running, lift the lid of the oil cap to check for smoke. If smoke is present, there is likely to be high engine compression. This could be caused by a faulty piston or piston ring, which may need to be replaced.
Step Four – Leak Down Test
The final stage of the process is to carry out a leak down test. Make sure that the valves on the cam belt are shut, then apply pressure to the cylinders one by one and listen carefully for any leaks. If you can hear air escaping, there is a leak somewhere which is likely to be causing low engine compression.
Can You Fix The Problem Yourself?
If you go through the above process and you are able to diagnose the cause of the compression issue, then you might be able to fix it yourself. Or you might be able to order the replacement part and find a mechanic to fit it for you.
If you cannot diagnose the cause of the compression issue then you will need to take your vehicle to a mechanic who will be able to complete a more in depth review.
Engine compression is vital for the vehicle to run smoothly. It is important to monitor the engine compression and fix any problems as soon as possible.
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