Renault Duster 1.5 dCi K9K: Low Compression in Cylinder Diagnosed with USB Autoscope IV

[00:00:03]Hello. We start the engine.

[00:00:18]>> This is how it runs.

[00:00:35]Now we shut it off. By the sound of the engine, it feels like one of the cylinders has low compression. Now we are going to connect the USB autoscope for oscilloscope and CTI 1000 current clamp.

[00:00:48]Then we will crank the engine with the starter. The high-pressure fuel pipe has been disconnected beforehand so that the engine will not start.

[00:01:05]>> During cranking, we can hear that one cylinder is skipping compression, meaning it does not create normal resistance during the compression stroke. Now, we run the diagnostic script called LP power and check the result. In one of the cylinders, the compression is less than 30% of the normal value. The starter speed is about 170 revolutions per minute. It is not ideal, but it is sufficient for this diagnostic test. The customer came in with a complaint that the engine misfires when cold. This is exactly the cylinder where compression is being lost. There was also a fault code for cylinder number four. And now we can see that this cylinder indeed has poor compression. Our next step is to check crankase gases and evaluate the condition of the cylinder piston group.

[00:01:46]We also need to check valve sealing. The most likely cause is leaking valves.

[00:01:50]After inspection, we found that the intake valves were too tight, especially on cylinder number four. After adjusting the valve clearances, the compression was restored.