Just a question as I don't know the answer, does the pressure remain in the fuel system, hp pump to injector, when the engine is stopped or does it return back to the tank ? I remember on cummins engines fitted with common rail that when you removed the injector feed pipes the pressure had dropped as soon as you stopped the engine, admittedly these were mechanical injectors not electronic.DPF does NOT cause this lack of regen of the DPF COULD but you would have other symptoms if your DPF was blocked/not regenerating
Leaking injectors could be the cause leaking injector pump can also cause it either of those will cause diesel to end up in the sump.
Injectors can leak when stopped leaking off the fuel pressure filling the bowl in 1 piston then running down the bores into the sump this could also cause poor starting first thing.
Many thanks Nick, interesting system obviously revolutionary in its time particularly when introduced. Can see why I haven't come accross it before as it is peculiar to Cummins and my commercial experience is really with Volvo and Scania. No it is different from what we think of as common rail injection today. In modern common rail the rail is held under extremely high pressure, sometimes in excess of 1000 bar, the rail also doubles as an accumulator and injectors are electronically controlled. As far as I am aware the rail doesn't intentionally depressurise so faulty injectors can leak diesel into the cylinder. The article I read said that the PT system still exists in part but is now computer controlled and I wonder if it is used in the cummins QSK series engines that are widely used accross the rail network.Going back many years to the cummins V8 and straight 6 which both had common rail manual injectors. All engineering staff , including myself, were sent on a course at Cummins Daventry based on adjusting injection rates using a dial gauge. To be honest we found it easier to send the vehicle to the local cummins agent for this type of work. The fuel system was known as the, if I remember correctly, PT system where you had a high pressure pump feeding all the push rod controlled injectors., no electronic injectors in those days 1967 to 1980 onwards.