Citroen Jumper 2.2HDI 4HV 2009 Runs on 3 cylinders

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Citroen Jumper 2.2HDI 4HV 2009 Runs on 3 cylinders

Postby Martinjensen » Wed Mar 07, 2018 4:14 pm

This Citroen was towed in with a customer complaint that it runs on 3 cylinders, and there is a loud knocking or puffing noise from the engine

1.PNG


The first thing I did was to perform a relative compression test, to verify the mechanical state of the engine. Something is definitely wrong with this engine, lets look at the details.
Blue: Starter motor current

2.PNG


The amperage consumption for cylinder #4 is very high
Something is clearly wrong with cylinder #4, or is there???
Blue: Starter motor current

3.PNG


Lets look at what the cylinders are doing on 720 degrees of crank rotation. The firing order is 1-3-4-2
Blue: Starter motor current

4.PNG


I wanted to gather as much evidence as possible before opening the engine. So I mounted the WPS in the exhaust and cranked the engine again. The pattern is not uniform, we will look at the details later.
Blue: Starter motor current
Red: Exhaust pressure


5.PNG


This capture is made with the WPS mounted in the intake manifold. Notice the peak that matches the high current consumption for cylinder #4
Blue: Starter motor current
Red: Intake pressure


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If we look at the intake pulsations in details we can see, that when the intake valve on cylinder #1 opens. Instead of a drop in pressure, that we would expect from a normal cylinder. We get a burst of pressure in the manifold.
Now we are on the right track.
Blue: Starter motor current
Red: Intake pressure


7.PNG


Lets look at the details from the exhaust pressure waveform
Blue: Starter motor current
Red: Exhaust pressure

8.PNG


If we compare our waveform to the piston position chart, we can se that the exhaust valves on cylinder #1 is not opening. But why would this give a high current consumption for cylinder #4, and a pressure burst in the intake?
Blue: Starter motor current
Red: Exhaust pressure

9.PNG


I then moved the Pressure transducer to cylinder #1. Now it is 100% clear that the exhaust valves on this cylinder is not opening. Resulting in an additional compression event, instead of an exhaust event.
Because its companion cylinder (Cylinder #4) is on its compression stroke, and this cylinder (Cylinder #1) is also compressing the trapped air on the exhaust stroke, the starter motor requires allot more current to rotate the crankshaft past this point, resulting in the large current rise on cylinder #4 compression stroke.
When the intake valve for cylinder #1 opens, this trapped and compressed air is released through the intake valves and into the inlet manifold, resulting in the large pressure burst we could se in the intake pressures.
This release of pressure almost sounded like a small gun shot.
Blue: Starter motor current
Red: In-cylinder pressure, cylinder#1



10.PNG


Now with all the evidence gathered is was time to open the engine.
As you can see from this picture the 2 exhaust rocker arms for cylinder #1 was destroyed.

11.PNG
Martinjensen
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Re: Citroen Jumper 2.2HDI 4HV 2009 Runs on 3 cylinders

Postby Steve Smith » Fri Mar 09, 2018 3:27 pm

Thank you so much for sharing this case study.

This highlights one of the many features of the WPS pressure transducer when it comes to evaluation before intruding into the vehicle and starting the disassembly process.

Had we used a compression gauge to measure compression, the values obtained would have been good and the potential to move one and miss the error is high indeed.

I speak from experience where I missed this exact fault with a fractured rocker using a compression gauge.

Thank you again, take care......Steve
Steve Smith
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