My fuel pressure is approx 2700 while cruising. 1700 at idle. Anything over 20% throttle dips down to 2100. This is consistent...

Im trying to hunt down 2psi....recently started logging FRP and noticed this trend. Is it doing higher Pressure during Cruise to atomize for fuel economy? Or is my pump jazzed.

 

what's the "2Psi" significance ?

Read the duty cycle of HPFP regulator solenoid to understand what ECU is trying to regulate vs. rail pressure.

What is your mileage ??

 

It used to hit 18psi + no problem, now im struggling with 16. Sometimes peaks at 17.2 ... its noticeably slower.
170km on it.

 

That is 105k.Mi: right on the mark!
HPFP + Roller bearing
Do the PCV maintenance at the same time.

 

I just had the pcv replaced under warranty. It was leaking I wish they would have mentioned it. Ill have them run a diag on the pump if its trash, hopefully warranty will cover it.

 

You can do this job your self... I replaced my low pressure fuel pump (in the gas tank) for $280 (https://www.mbpartsource.com/oem-par...ule-2134707401)

No need to replace the HPFP on the engine. Just replace the tappet that it rides on where it touches the camshaft. The tappet costs like $50 at Mercedes.

I have 159,000 Miles (255,885 kilometers) on my E300 and had the same symptoms. Changing the fuel pump in the gas tank will fix it without doing anything else, but replacing the roller tappet is strongly recommended.