I'm having an intermittent no start problem with my 2000 C280, 45m. The car will crank but not start. After a start the car drives perfectly, no stalling or dying. Never happens on the first start of the day. It has been unusually hot out here lately. The car will not restart sometimes after 10 minutes sometimes after 2 hours. If you just wait awhile, it will start. After doing a bit of reading I thought I'd change the CPS. The only difficulty is that you need an E8 Torx socket. Autozone has a decent set for $17. Take the screw out first and pull out the sensor and then remove the connector. There is a small O ring. There are two types for specific engine numbers. After I put in the new sensor, the car started and worked fine over the next day with about 10 starts. Then it failed to start after sitting in our garage for 2 hours. It started again after just waiting a bit. Battery is fine. I gather from other threads that the CPS does not throw a code. Would a failing fuel pump relay throw a code? Is it possible I got a defective part? A poster at another site solved his problem with a second sensor. The one I put in was original Mercedes OEM.

Any ideas?

Thanks,

glenmore
1991 300CE
2000 C280
1990 LS400

Fuel pump relay. Easy to get to in the trunk. I think it's OK to throw a (inexpensive) part at the problem if there's a high likelyhood you'll be replacing it anyway in the future. The fuel pump relay is one of those parts. Crank position sensor is another but you've already taken care of that one.
Good Luck, Dan

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2012 E350 Bluetech