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Your ECU says fuel pressure P1141 and your driving reports matching issue... this is confirmed.
It's either low side or high side pressure.
Both sides go bad around 100kMi... your pick!
Choices are ... :
Dirty tank-pump filter
Charcoaled pump connector
Tired HPFP shaft + roller
(defective pressure sensors: unlikely)
You can troubleshoot fuel pressures to then focus on low pressure side only - Save high side for later.
Personally I think it's the standard "dirty old filter" that would benefit a little tank cleaning job.
The parts-canon has limited success rate offset only by high-profits... so it's best to measure tank pressure using your scanner then decide to inspect pump connections under passenger side rear seat.
Hope this helps guide your testing for quick fix. Tank ring best requires a tool + new ring O-Ring seal... no need to drop down this MB tank!!
Master Surya recomands "LAUNCH codeReader Elite" or better : ~ $120 - This unit will read your fuel data. LAUNCH is the real deal ✌️
Last edited by CaliBenzDriver; Jun 23, 2025 at 11:29 PM.
Fuel pressure should remain at 2900psi at full throttle. Only on idle it lowers to ~2175psi.
As your fuel pressure can reach 2900psi under normal load, first thing to check would be fuel flow, is there enough pressure and volume on the low pressure side of the fuel system.
Can you measure the low pressure fuel pressure under at full throttle?
When my in-tank fuel pump needed to be replaced, I was getting P254000 "The signal for the pressure sensor of the low pressure fuel circuit is implausible".
I didn't actually check that pressure before replacing the module, but I would assume either a very high or very low pressure would trigger an "implausible" situation/code.
Did a long drive today. Had a hard time replicating the problem. Only very slightly rpm fluctuation and surging at highway speed this time.
Anyhow, difference between turbin and shaft were always around 50 rpm +/-20. There were no difference in the values when the problem occured and when everything was normal. No spikes in rpm or similar so I guess no problem there.
Fuel pressure at rail was constant at around 2,836-2,900 psi.
Something interesting was that the tourqe app picked up fault code p1141. Icarsoft did not see the code. Which according to my understanding can be fuel issue or intake runner flaps among other things. My engine does not have the three problematic actuators on front but instead only one. Engine code is 272984 31 728445.
What do you guys make of this?
I'm not sure but I think the problem might be getting worse when I'm low on fuel leading to believe I might have dirt in the gas tank. But at the same time, dirt in the gas tank should give me more problems than rpm fluctuation at highway speed? Pressure looks good as well so there should be no problem with fuel pump and filter?
The information I marked red : Your engine is M272 as per 1st post , correct ?
If indeed M272 which is commony a port fuel injeciton ( low pressure max 70psi) , unless special rare version with GDI........... is your M272 GDI version ?
Anyway be it port or GDI version, fuel pump pressure at the tank can never be at 600-700 ish PSI as per you post #32 "At steady highway fuel pressure at pump sits around 630-650 psi. At full throttle pressure at pump fluctuation heavily between 630-700 psi. Normal?"
70 psi is as high as it will go for low pressure fuel pump in the tank.
Either you sensor at fuel filter went bad, or your scanner is reading wrong.
Last edited by S-Prihadi; Jun 24, 2025 at 10:14 PM.
It's a normal m272. I'm terrible sorry. The fault is on me when I converted from bar to psi. Correct at pump is 4,4-4,5 (63-65 psi) at steady speed an fluctuation between 4,4-4,8 (63-69) bar at full throttle
It's a normal m272. I'm terrible sorry. The fault is on me when I converted from bar to psi. Correct at pump is 4,4-4,5 (63-65 psi) at steady speed an fluctuation between 4,4-4,8 (63-69) bar at full throttle
At more or less all conditions expect full throttle the pressure at rail hovers around 2900 psi. At full throttle it goes down to about 2000 psi.
Was thinking about my maf as well. At idel it's about 5,3-6 g/s. Driving steady at 80 kph and 1500 rpm it sits around 13-15 g/s. At full throttle pull for a few seconds it goes up to about 150-200 g/s. Normal?
At more or less all conditions expect full throttle the pressure at rail hovers around 2900 psi.
At full throttle it goes down to about 2000 psi.
Was thinking about my maf as well. At idel it's about 5,3-6 g/s. Driving steady at 80 kph and 1500 rpm it sits around 13-15 g/s. At full throttle pull for a few seconds it goes up to about 150-200 g/s. Normal?
MAF sounds right but not HPFP.
It's both too high and too low.
It's supposed to be in the middle and stay near there.
Your low-side fuel delivery being proven right already...
look at the "proportioning valve" actuation data to confirm it bad.
You're likely to find it maxed out to signify your pump has lost ability to regulate rail-pressure.
I will contact the Indy tomorrow and ask for a diagnosis with xentry.
Something I do not understand if this is the problem:
Why don't I notice any power loss at full throttle?
Why doesn't I have any real change in pressure when the rpm fluctuation occurs at steady speed, it stays around 20 000 psi +- a few hundred.
Why did the car work ok for a while after I fixed the bad o ring and had the battery off? The problem came back totally random when driving on the highway at around 130 kph for about half an hour.
Is it common for high pressure pump to fail at this milage? Car only has around 62 000 miles. Always serviced at MB.
Let's hope for the reg if anything of those. Even though the reg is ridiculously expensive as well.
I will contact the Indy tomorrow and ask for a diagnosis with xentry.
Something I do not understand if this is the problem:
Why don't I notice any power loss at full throttle?
Why doesn't I have any real change in pressure when the rpm fluctuation occurs at steady speed, it stays around 20 000 psi +- a few hundred.
Why did the car work ok for a while after I fixed the bad o ring and had the battery off? The problem came back totally random when driving on the highway at around 130 kph for about half an hour.
Is it common for high pressure pump to fail at this milage? Car only has around 62 000 miles. Always serviced at MB.
Let's hope for the reg if anything of those. Even though the reg is ridiculously expensive as well.
The MB specialist with Xentry will be able to use Xentry to troubleshoot exactly and test what's wrong.
20 000 psi is way too high.
The rail pressure needs to be regulated so fuel can be metered precisely: Not +/- 1000.Psi range
It can still be many other things to do with ignition and computers.
The fuel pump normal lifespan is longer than 60kMi.
You do have a fault that points to fuel delivery - That's were this issue landed you.
What's making your rail pressure so wild:
the HPFP pump or it's M272 external regulator or the sensor ?? M272 GDI fuel rail
Bad sensor would allow a well regulated pressure to be reported as bad.
Last edited by CaliBenzDriver; Jun 25, 2025 at 08:18 PM.
The Mercedes specialist is on vacation so no help there.
I did get the launch scanner and did some more test.
Also I have the very expensive gdi pump running of the cam.
The code p1141 is rail pressure to high according to launch.
Rail it's at 200 bar +/-1 at all conditions expect under heavy load, then drops down to around 150 bar.
Pressure at pump in tank when I tested today sat at 5.85 bar at ideal, drops to 4,5-4,7 at steady highway and under load.
Also found this post, same engine and gdi pump. He changed the pump but did not get any improvement. I were about to change fuel filter but never got back with the result.
Could this be a bad fuel filter? It has never been changed.
I tried to look for the high pressure proportion value, the only thing I found was high pressure regulator or something like that, sits at 0% during test
Edit: it was on/off ratio of pressure regulator valve
The Mercedes specialist is on vacation so no help there.
I did get the launch scanner and did some more test.
Also I have the very expensive gdi pump running of the cam.
The code p1141 is rail pressure to high according to launch.
Rail it's at 200 bar +/-1 at all conditions expect under heavy load, then drops down to around 150 bar.
Pressure at pump in tank when I tested today sat at 5.85 bar at ideal, drops to 4,5-4,7 at steady highway and under load.
Also found this post, same engine and gdi pump. He changed the pump but did not get any improvement. I were about to change fuel filter but never got back with the result.
Could this be a bad fuel filter? It has never been changed.
I tried to look for the high pressure proportion value, the only thing I found was high pressure regulator or something like that, sits at 0% during test
Edit: it was on/off ratio of pressure regulator valve
You are getting it....
rail pressure pegged at 3000Psi 30% too high!
pressure regulator sits at 0%
WHY is that...
How does this regulator work, with a diaphragm??
Everyone can jump at the bad regulator but maybe the pump is poorly controlled and killing its regulator with a high output.
I don't know this particular pump + external regulator.
Try to figure what controls if any are on the pump itself.
Basically the working ECU control is unable to regulate down the rail pressure.
Last edited by CaliBenzDriver; Jun 28, 2025 at 06:20 PM.
Can anyone confirm what the pressure value on fuel pump should be at idel and under load?
Also how the high pressure system work? What are normal values? I tried to look in WIS but my version did only have for old engines for some reason even though I looked at vin.
Can anyone confirm what the pressure value on fuel pump should be at idel and under load?
Also how the high pressure system work? What are normal values? I tried to look in WIS but my version did only have for old engines for some reason even though I looked at vin.
The two links you posted, those are me.
........
I wonder what you and Cali is smoking which I want in too
You confirmed on post #36, 4 days ago .....your engine is NORMAL M272 which means is a port fuel injection....which means you wont see pressure at injector higher than 70 ish PSI or 5 BAR
...which means your engine does not have HPFP ( high pressure fuel pump )
.
And then you and Cali go on and on about pressure regulator which exist on the rare GDI version M272 with High Pressure Pump , code M012 ......
So which M272 version is your engine ? Port fuel injection or GDI version ???
Pass me ur VIN and I will tell you with 100% accuracy......... what fuel injection your M272 is. Port Injection or GDI .
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