Fuel Pressure HPFP
Thread Starter
Junior Member
Joined: Jun 2024
Posts: 22
Likes: 3
2017 e400 Estate
Fuel Pressure HPFP
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.
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.
Out Of Control!!
Joined: Apr 2019
Posts: 12,058
Likes: 6,857
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
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.
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.
Read the duty cycle of HPFP regulator solenoid to understand what ECU is trying to regulate vs. rail pressure.
What is your mileage ??
Last edited by CaliBenzDriver; Feb 20, 2026 at 04:22 PM.
Thread Starter
Junior Member
Joined: Jun 2024
Posts: 22
Likes: 3
2017 e400 Estate
Out Of Control!!
Joined: Apr 2019
Posts: 12,058
Likes: 6,857
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Thread Starter
Junior Member
Joined: Jun 2024
Posts: 22
Likes: 3
2017 e400 Estate
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.
Super Member
Joined: Aug 2019
Posts: 594
Likes: 171
From: USA to Germany
W221/W222/W213/X290
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.
