This is the picture of a piston. To be more accurate, the number 2 cylinder piston of a common rail direct injection diesel engine used in a light truck. The truck is on the road now, with a new engine. I keep this piston in a small cardboard box, under my office table. I can flip open the box cover with my leg and have a quck glance at this piston from my seat whenever I feel like, without giving the slightest hint to the person sitting in my front what I am doing.

Why? Why I keep this under my table??

It was a simple complaint of engine not cranking. Looked like hydrostatic lock. Removed injectors. No liquids. But the engine became free. The problem was with number 2 cylinder. An endoscope gave a clear image. The deformed piston was contacting the injector tip just before its upward stroke ends and it was preventing the further rotation of the crankshaft. If the rotation is reversed now, it will be fine for another 360 degrees.

I was seeing a piston like this for the first time.

Excessive combustion temperature in cylinder number 2.

Excessive heat generation? Or, failure of cooling system to carry away heat from number 2 piston?

We decided on excessive heat generation… a defective injector resulting in incorrect combustion and subsequent overheating…

Why injector?

It was a common rail type… the fuel pressure reading was correct… pump flow control valve was working perfectly…no problems with the injector control circuit… fuel pipe from fuel rail to injector was in good shape, rail… it was just a pipe to me… We did not have the facility to test an electronic injector…

The injector was replaced with a new one. New piston, connecting rod , bearings…

400 km later the engine stopped again. To my horror it was the same problem in number 2 cylinder…

First ever misdiagnosis in engine mechanical in my career… there had been a few in NVH issues, in elecrical and electronics systems… but nothing as humiliating as this…

Time flies. I changed my table top calendar many times after that incident.

There are instances when I feel extremely proud of my skills in technical training, diagnostics, failure investigations… then, I will return to my seat… flip open the cover of the cardboard box… and my pride evaporates like a drop of spirit on a hot exhaust manifold.

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