Start it up and with a bright flashlight look for air bubbles in the fuel line that exits the back of the pre-filter housing where the bottom of the pre-filter would be. Air in that line means the pre-filter oring or the line attaching to the prefilter is leaking. Air getting into the prefilter is about the only point that can cause a running engine to die.

The exception being a leak at the oring behind the shutoff valve.

Is also possible it is the SOV or the K40 realy causing the problem. That usually kills the engine suddenly; "as if key were turned off" so is pretty obvious.

The MAF fault should trip the CEL and is usually immediately noticable; no turbo boost, difficult to get engine over 3k rpm's and accellerates like a 240D.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)