I have a frustrating problem with my 190Diesel.
Recently I noticed a leak in the middle of the one of the injectors, so I guessed that one of the injectors was just not tighten enough so I went to bosch service, they removed problematic injector and repaired it.
After that problem with nocking really started. Just like hammer banging on something metal. We checked glow plughs, checked all of the injectors but nothing. Problem was still present. After that, the diesel pump was dismateled and checked on the bosch table. All about the pump was in the factory range.
We even removed and checked pre chamber in the cylinder from where the noise was comming. Still, knocking is present.
I'm thinking to put new injector nozzles, but current nozzles are just OK, regarding pressure and fuel mist.
Any idea, please?

Remove the suspected bad Injector of and from the Cylinder and remove another from another Cylinder that is a Good Injector and put the Good Injector inplace of the suspected Bad. Put the Suspected Bad one inplace of the Good one.
With all the Injectors installed start the Engine.

If the Knocking followed the suspected Bad Injector it is an Injector problem.



If the knocking remains on the same Cylinder you have an issue with the Engine or the Fuel Injection Pump.

If your Engine has Hydraulic Valve Lifters. Perhaps one of the Valve Lifters has gone bad as they also make a tapping sound.

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84 300D, 82 Volvo 244Gl Diesel