My 2000 E 430 died on the freeway about 20 minutes after leaving work.

I had it towed to my driveway and the next day it started right up but quit after running about 20 minutes.

I changed out the Crankshaft Positioning Sensor as well as the fuel pump and fuel filter last year so I don't suspect any of those.

Any suggestions on what to try next?

As of this moment, it won't start, just cranks and stops.

Could be the CPS again -- always possible the replacement part was faulty.

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

Here's a trick MB roadside guys have been using for years. Run the engine until it stalls, then immediately pour water down on top of the CPS to rapidly cool it down. If the engine re-starts immediately replace the CPS. You could also bench-test if you've got an ohm-meter. Normal reading is ~1,100 ohms. If it goes open when it gets hot it's no good.