Don't you read anything I post? My first post had you to check output of rail pressure relief valve as part of your troubleshooting?
Am I wasting my time typing and researching parts and suppliers for you? I guess you would rather make your own mistakes then learn from others?
Typically, if the fuel rail pressure relief valve is bad, you'll have trouble starting (long starts/hard starts) because the fuel rail is unable to build up the minimum needed pressure (I think its 5000psi) to triger activation of fuel injectors.
I'm done posting on this topic. I've given you a source for a COFV and it doesn't appear you wish to follow my advice as the only person on this forum who has had the same exact problem and fixed it after wasting money replacing the in tank pump twice, the fuel control valve on the CP3, and a new fuel rail with a new rail relief valve, and finally the CP3 pump which only needed a COFV.
A used COFV could be bad and you can be chasing your tail if you test a defective COFV. You are willing to spend $300-$400 for a fuel rail relief valve but not less than $100 for a COFV? I dont' get it.
Good luck, here are some parts numbers for you.
This is the actual Bosch part number Car Part BOSCH 0 281 002 826 Pressure Control Valve, common rail system
ManufacturerBOSCHNumber0 281 002 826DescriptionPressure Control Valve, common rail systemOriginal numbers 6420780249, A6420780249Valve TypeDiesel
Analogous \ Similar Parts of BOSCH 0 281 002 826
ManufacturerNumberDescriptionMERCEDES 642 078 02 49Pressure Control Valve, common rail systemMERCEDESA 642 078 02 49Pressure Control Valve, common rail system
Mercedes Benz Fuel Rail