Diesel fuel needs correct atomization to be compressed to the point of combustion in a CI system diesel. Compression Ignition essentially describes the process pretty well. When a conical spray pattern exits the tip of the nozzle of an injector it is atomized into microscopic particles that combust under the extreme pressure and heat of each combustion chamber (cylinder). That is similar to using the glow plugs to pre-heat the combustion chamber so the engine will start when it's cold.
The fuel mix is also dependent on the precise timing of the combustion chamber piston position, the timing of the delivery of the atomized fuel and all parts of the mechanical fuel delivery system being in total sync.
Yes, one could monitor the crankcase on perfectly level surface at the same oil temp and amount of time for all oil to have drained back to the crankcase after each use, but it would be onerous and not very accurate at best , and who has the time to match the conditions to get an accurate read?
Here are some of the issues with unburned fuel: non- conical spray patterns, are not unique to diesels. L and K-Jetronic gas Bosch EFI and hi pressure auto fuel delivery systems suffered the same problems, mainly fuel leaking off the injector tip when it should be closed; fuel pissing onto the cylinder walls and running down into the crankcase, while 'cutting' the oil needed on the cylinder walls, when the engine is running. Any or all of these issues lead to compromised oil, main and crank bearings/journals being robbed of needed oil, etc. And in the case of the early 70's 6 cylinder Volvos building up enough gas & vapors of combustion to literally blow the oil pan off the engine when cranked to start.
To say nothing of the lack of power due to less combustion being created in the cylinders affected, and wasted fuel= greater cost to run, with less available power, and slow engine death.
Remember one has to be aware something is happening to monitor it. And it's pretty difficult to know an injector is not to spec on a diesel, unless there is excessive smoke present. And injectors on all vehicles are able to be tested and in many cases reset by qualified technicians with knowledge and experience/tools and parts available.
To understand how important cleanliness is when working with injectors/fuel distributors, and IPs, injection pumps, those who rebuilt them for large trucks, earth movers, etc, do their work in clean rooms with positive air pressure. It is very precise work, to say the least.
Here's a link to Bosch certified injector testing facilities and how they use strobes etc. to determine spray pattern, etc.
https://www.google.com/webhp?source...TF-8#q=clean+room+injector+rebuilding&spell=1
Hope this answers your questions.
BTW, some of the videos are very interesting, IMHO.
