RIP CM2250, 2013, 800,000km 20,000 hrs

[Rawze]

(08-04-2022 )Hermjeji Wrote:  ...
What am I missing?

On a common rail engine .. the commanded and measured fuel rail pressures will normally be off by up to about 300 bar, maybe a bit more under high loads. This is absolutely normal.

This is because the design for the rail pressure circuits are known as a hydraulic "Bypass-Charging" system...

--- I.E.> the pump provides all the flow and pressure that it can make to the rail because a bypass valve closes, diverting it all to the rail ... and once it reaches the commanded pressure, the bypass valve opens and makes the fuel pump go into a hydraulic state of "neutral", it not providing anything any more. It stays there in neutral until a set amount of fuel is consumed and the pressure falls off again. The pressure has to bleed back down on its own to about 300 bar or so below the commanded pressure before the valve is closed to make it pump again.

That is how it is supposed to work, so that the bypass valve is not over-worked to death due to having to try to make an exact pressure all the time, also so that the pump can go into neutral to cool off between feed cycles, and finally, so that the fuel temp itself does not get extremely hot due to massive pressure drops that an old style ball-spring regulator would suffer from at those extreme pressures.

The data in the screen above seems to reflect this as well. and looks ok for the most part to me.

and BY THE WAY.... That injector performance test.. and the cylinder performance tests ARE ABSOLUTELY AND UTTERLY USELESS!!!.. IT IS COMPLETE GARBAGE!!!.. STOP USING IT TO GAUGE YOUR ENGINE BY!!!!... IT WILL FAIL PERFECTLY GOOD INJECTORS.. AND TELL YOU THAT BAD ONES, THAT THERE IS NOTING WRONG!!... -- THAT PERFORMANCE TEST SHOULD NOT EXIST IN THE ENGINE SOFTWARE --- stop using it.. just stop!!!!!!


DO THE TESTS RECOMMENDED ON HERE, like the injector leak-down tests.. cylinder cut-out tests... run the engine on one cylinder at a time, etc... and then follow it up with removing all the rocker shafts and checking for valves that do not seal by pressurizing the intake manifold to 30 psi with all the valves in the engine closed (compression-loss test). - Those are how you properly test everything and if it passes all of that with flying colors, then there is noting wrong.. you ARE CHASING GHOSTS!

Also.. look to see what the ecm is actually doing commanding, etc. ...
GET SOME desktop recording software and use this screen file for Calterm to record ALL of the settings on there.. and post screen shots of it. That will tell you everything going on inside that ECM and what that computer is doing...
ref: http://rawze.com/forums/showthread.php?t...6#pid28636