DCI problem!!

Nissan Qashqai, stop start fault. I bought a dci Qashqai a few months ago, car has been broken more than I’ve been driving it. The dealer says there is pollution on the engine, but every time it comes out negative. My theory is that the injectors injects too much diesel in the engine, and blocking up the whole system. I mean really 9.6 l per 100km?? The whole idea of a Diesel engine is to use less fuel?? Can Nissan please sort out this problem cause I’m getting sick and tired!!!