I have had issues with my E350 that I am sure are fuel related. I will try my best to explain. When I cold start the car I turn the key to position 2 measure the fuel pressure which is 55psi. Every now and then after a 20-30 minute drive I return to the car to crank and it stumbles and dies then refuses to start for about 15-20 minutes. I replicated the issue and as I suspected the fuel pressure on the rail dropped to less than 10 psi which I feel caused a vapor lock scenario which explains why this stumbling and dying issue only happens when the car is up to temperature. Another thing I noticed is that the fuel pressure generally runs around 35psi when the motor is warmed up. So i dug into the fuel system and did a dead head pressure test on my fuel pump and it showed 85psi which is good. So being close to the fuel filter service (79000miles) I went ahead and purchased a new one. I have installed it and cranked the car up and as usual on cold start it pressures the system up to 55 psi. I bled the pressure off of the system to read pressure once the car was warmed up and to my dismay I am again showing 35psi. I thought maybe an injector is stuck open but I dont see that being the case. I have not driven the car since the filter swap but I am concerned that im missing something. I cannot find a fuel return line going back to the fuel tank I dont think this system has a fuel return. i have also done a pressure drop test and I loose about 8 psi in a couple of hours. I am mechanically inclined and have worked on cars before but this is my first mercedes. Ive had a host of other issues ive fixed since obtaining this car and the fuel issue is getting the best of me.

today I disconnected the fuel rail from the supply line under the hood and did a pressure test. 50psi on the line and 42psi when reconnected and checked at the valve on the rail. I am going to buy a pump relay although im certain its not the problem. I am starting to think the pump is suspect. If anyone can PLEASE comment on this issue if I am missing something. I am also considering splicing in a check valve after the filter under the passenger seat.

anybody?

Check if pzev gas tank, pump is not replaceable by itself only available as complete gas tank, has extended warr if pzev 10 0r more years extended

its not pzev im located in Louisiana

I don't suppose this car has a fuel pressure regulator? Dropping fuel pressure on older injected cars is sometimes caused by this fairly simple device, but I have no idea about your E class. Good luck and hope you solve the problem.

Rgds,
Chris W.
ex E300D, 467K

__________________
Objects in closer are mirror than they appear.

Regulator is part of the filter. Just quit screwing around with it and put a pump in it.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

yea I figured such ordered the pump yesterday waiting on it to come in. Just making sure im not missing anything else. thanks