08 ML320 CDI
109K miles

Recent Changes/Maintenance
Oil Cool gasket fiasco
EGR Delete
DPT Delete
Swirl Valve Delete
K&N air filters
Fuel Filter
Glow Plugs
O2 Sensor
Oil change
Power steering fluid change
Coolant flush/change

History
Unkown just purchased used vehicle before maintenance

Symptom/Problem
Down on power and fuel economy. On my trip I noticed that it struggled on small hills to maintain 80MPH towing about 1200 lb. I kept pushing it for an hour, economy was down to 13.5. CEL and no power. Pulled over and found a fluid dripping from under the engine. After it cooled it seems that it was diesel. Currently no start condition to troubleshoot possible fuel leak.

Engine codes
P2242 - O2 Sensor Positive Current Circuit High (Bank 2 Sensor 1)
P2211 - NOx Sensor Heater Sense Circuit High Input (Bank 1)
P2021 - Intake Manifold Runner Position Sensor/Switch Circuit Low (Bank 2)
P2047 - Reductant Injector Circuit/Open (Bank 1 Unit 1)
P2017 - Intake Manifold Runner Position Sensor/Switch Circuit High (Bank 1)

Where do I start troubleshooting? I was going to pull the hose off the fuel filter and check for fuel flow.

LMAO not the first person to ask why I bought it or recommend to run. Unfortunately the SUV diesel options are limited and with VW's fiasco it became even more limited. I've already got too much time and money invested I'd like to finish and get this thing somewhat reliable.

I found the issue easy enough, well at least for the fuel spewing out. The fuel tube that connects the fuel rails ripped out of the right side. I've ordered a new fuel rail but don't seem to be able to find the part number on that crossover pipe.

Since it sounds like you might need few parts -consider subscription to MB EPC for about $80 a year.
If not - MB of Atlanta is having good part catalog on the web

Sorry was out for a few days and didn't get on the computer. Playing on a few sites, MB of Atlanta being one of them I was able to find some part numbers. I've got the parts on order and racking my brain trying to determine if there was any way I over/under tightened the nut. I definitely didn't crank on it too tight as I know most pipe style fittings don't need to be much more than snug. I'm thinking possibly under tightened or missed tightening it by hand since I had it off/on so many times. Maybe the pressure from the system blasted the threads off. Either way parts on on order as well as a iCarsoft scanner so I can monitor the rail pressure and other monitors to see how the system is functioning.

So my problem continues. I got a new fuel rail and crossover pipe in the mail today. Put them on and made sure every connection was tight, little more than snug. Drove it around town for dinner and no issues and seemed to have more power than before. I decided to actually floor it right before my house for a quick 0-40MPH, check engine light on and the engine dies. Had to tow it up the drive way with the Jeep.

Pull the cover off and find that it blew off connection from the fuel rail to injector #3. What could be causing this? I now need to order another fuel rail and no clue what the problem could be.

Is there a pressure regulator on these things?
If there is, is yours working or are you going so far overpressure (already high on a common rail system) that the weakest link is blowing out? You mentioned getting an iCarsoft scanner - what is it telling you for fuel rail pressure (requested vs actual)?

Unfortunately this was the first drive and even though I had the scanner in the car I was just going to dinner and back to make sure it ran so I wasn't diagnosing anything. It took it 150 miles to blow off the first time and only under continuous load, didn't figure one little sprint up the road was going to pop it like that.

My $12 Bluetooth adapter reads rail pressure.
Coming from Ford 6l, monitoring the engine all the time is normal for me.
In situation like above, that would help a lot.