Tutzi

Hello,
i must go to work. i will read your post later,after work . here i give you some documents. bye

S-Prihadi

Sas,
Looking at your LP fuel pressure from..............
01. BEFORE ENGINE START, COLD : 5.6 BAR
02. Engine Start, cold , 1,187 RPM : 4.5 BAR / 4.8 volt at 1.75amps
03. Idle 785 RPM : 4.6 BAR / 4.7 volts at 1.7amps
04. Rev up 4,368 RPM : 4.5 BAR / 4.9 volts at 1.9 amps

It seems kind of Flat Low , the fuel pressure for 02 to 04 for your car. I mean its Low always .
Engine OFF at 5.6 BAR doesn't count, because there is no fuel flow, so it is easy to hit 5.6 BAR.

See below a new vs old fuel filter with engine rev up, but car is stationary.

I am wondering, does a P254000 DTC also flag a "flat" fuel pressure curve like yours as a Fault ? The Xentry explanation emphasize 10 BAR up as Implausible fuel pressure and the trigger to flag a fault code....hhhmm.
I think you need to do screen record and do a test like I did, while stationary.

========================

The High Pressure fuel strategy seems different on your 3.5L compared to my 3.0 Turbo.
At idle I get lower fuel pressure (118 BAR ) than yours, but higher fuel pressure 180 BAR at higher RPM but under 3,500RPM ish and throttle body opening not too big.
If I do full wide open throttle, I also get 150BAR all the way to redline RPM.

Tutzi

Hello,

much to read...with litttle bit help of google translator ;-).

1. After i read the explanation from the fuel-system and got the information from you with the dtc - over 10bar, i have really the supposition that the 55/2b valve could be the problem. Last evening i bought a used fuel filter at ebay. I think about to change the original 55/2b from the Hella Filter with the original used one. Of course only if both are changeable with each other.

2. I don'tthink that the low fuel pressure sensor is defect, cause my old filter hasn't this P25400 mistake. Only after the fuel filter was changed with the new hella one, the mistake comes. And now my good old origin sensor make this mistake,too. So i think like you, that it is a mechanical problem.

3.In xentry you can look the freezeframe at a line diagramm (graph chart). I was driving the car and watching the line chart along the way. I didn't see 10bars. But i also noticed the xentry is slow with freezeframe. I'm going to for a ride at the weekend and will directly start the freezeframe befor engine start till i'm on the highway. I will look that i can make this monitor recording in the next time. I have Win XP ;-)

4.the low pressure is controlled with the fuel temperature. So at could the pressure is round about but over 4,5bar and later roundabout 5bar to 6,5bar.

5.the high pressure is in Gear Position P and N about 150bar, but if you drive the car the pressure gets higher to roundabout 200bar.

6.My old filter: The filter was 10years and 98thousand kilometers in the car. The P08700-mistake come only very rarely. Of course i opened the filter to see how it looks like. Unfortunately I already threw it in the trash :-( So two things i don't have now... the 55/2b valve and the filters...
I texted a freiend on the side and asked him for the pictures i have make. I put in here.




7. Can you compare your voltage and ampere values with mine under consideration the low pressure? I think that my values are little bit lower as yours?

8.Look at the p254000 pdf - the measure pressure and the target pressure. (i think that it is target pressure)

9. I read some information about the wirings and the mass -connection. I have controlled and cleaned the mass connection from N10/2 (SAM Rear) and from N118 . In addition to that i have controlled the wiring from N118 to the Fuelpump. The cables from the low pressure-sensor to the n118 i made a resistance measurement of the three cables, al have the "same" low resistance und no connection to each other. The cables looks good, the mass point looks good too,but nevertheless i cleaned them.

S-Prihadi

Sas wrote :
7. Can you compare your voltage and ampere values with mine under consideration the low pressure? I think that my values are little bit lower as yours?
All data I have posted on the 2 links, you can check them.
Also if you want to compare data, you also must do screen recording because 1st - Xentry is lagging too, 2nd - there are pressure swing which only visible by recording, I know the graph facility but I don't like it, it is even slower than digits.
The best data is you must do 1st and 2nd gear full power to redline 6,200 RPM road test, this is the time when any bad pressure data can be seen. Idling/stationary test even if we can do 6,000 RPM is a NO-LOAD test and for fuel burn, it is low and the pressure wont be
accurate. Fuel flow and pressure is inter-related, just like any pumps.


8.Look at the p254000 pdf - the measure pressure and the target pressure. (i think that it is target pressure)
When I use google to translate, I do wonder why Fuel Pressure 4.5 BAR ABSOLUTE ???? Fuel pressure we do not use Absolute gauge or value.


7.05 BAR measured pressure is not a problem. The overflow supposedly only open at 7-9 BAR, so that is why 10+ BAR is the alarm level, but not 7.05 BAR.
Do not get too focused on the duty cyle of 68%, because it is never a guarantee that 100% is the maximum, it can be lower than even 80%. I do not know why my N118 does not give me duty cyle..I do not have this data.
6.6 amps is a lot, mine at maximum is never higher than 7 amps. So the amperage looks good.

Your old fuel filter paper look cleaner than mine ...LOL....while u done minimum 10,000 liters fuel burn or double than mine, I am sure.
That means my assumption is correct, the level of cleanliness of my country fuel station's underground tank is bad.


I hate to say this, but many people who does not use genuine parts, do have a lot of trouble....more so if they buy some China made junks/garbage.
Even if your Hella is good quality, its operating profile may not matched to the original fuel filter from Mercedes ( I do not know the actual fuel filter brand for your car, mine is VDO ).

Let's assume your engine can run well with fuel delivery volume of this Hella fuel filter, but if the N118 does not like the pressure and voltage/amps/duty-cycle/RPM "values" and keep producing DTC P254000,
what are you going to do ?

Tutzi

I looked at your values. I will do a little comparison. I will deal with the screen recording function, and the i will make the tests in the two first gears.

Afters this i will change the valve with the original one which i just bought. and then i do the same tests. If this doesn't work i will think about a new original fuel filter.

The Company HELLA is actually a very good quality brand...it is OEM like BOSCH...but...they probably just buy certain parts on the market where the quality is not so good :-(

Little Information spritmonitor.de ;-)

I drive the car since 2013 . All in all 74745 kilometers and uses 8872,8litres fuel (not less than 95octane)

EDIT: In my german functional-discription from mercedes two pressure are written at normal operation (Normalbetrieb).

A: Fuel pump pressure dependent of Fuel temperatur - 3,0 - 5,5 bar

B: Fuel pre-supply pressure dependent of Engine rpm AND fuel temperatur - 4,5 - 6,7 bar (absolut)

S-Prihadi

I have no doubt Hella is a good brand, I do trust Hella.
However fake ones are now plenty and we must be extra careful.
If you see my test drive with new fuel filter, 5 - 6 BAR is what I get most of the time.
You must remember that : the fuel line between fuel filter to engine is producing resistance of 1.1BAR ( static head ).
So 5.2 BAR is the minmum pressure you must get at the filter housing sensor, because the HP Pump at engine needs 4 BAR minimum.


Nice, for this information : https://www.spritmonitor.de/de/detai...html?cdetail=1
All in all 74745 kilometers and uses 8872,8litres fuel (not less than 95octane) <<<< yep, that means your fuel is cleaner than mine, of course....you are in Germany hahaha

Me drive very hard, usually best polite driving average is 7KM per liter or 14L per 100KM. Sometimes as low as 5KM per liter or 20 liters per 100KM.
My city is super traffic jam, average 20KM-H since day 1 to now at 36,000KM. My car ages more by engine running hours than by mileage.

Tutzi

Hello,

the used original filter arrived today. In the next days i will change the valve in the Hella filter with the original. I will tell you the results.

S-Prihadi

Did u actually manage to see what is the pressure reading on the Hella filter for 1st and 2nd gear maximum RPM pull ?
Can that valve fit Hella correctly ?

Tutzi

So here are the videos: New mercedes lowpressure fuel pump with Hella aftermarket fuelfilter. Unfortunately it rained before and i had a little bit wheelspin and the drive slip control was temporary active.

the first video is bad, but i saw no lower pressure than 4,5bar.

Stationary idle to soft limiter
stationary idle
First run - bad quality
Second run -

S-Prihadi

Wow....Your filter pressure is BAD under load/consumption.
When you see its goes up, that is when you car change gear and fuel flow slows down. Same as my car when using old filter.

The TILL STANDING video is weird the pressure, it can drop so low.

I sure hope it is the Hella filter regulator as problem and not also your pump.
Your pump amperage respond looks good though.

There is what pump technician called as affinity law, I believe our fuel pump even though the impeller design is not the same, follow that law too.
https://jmpcoblog.com/hvac-blog/pump...e%20horsepower.
What I am trying to explain is, only when the fuel flow is high...amperage then can be high. Therefore, if restriction exist in the sytem the flow is reduced, amperage wont go high.
This is without any mechanical or electrical problem on the pump. I am speaking purely about pumping liquid.
However pump's capability is HEAD (pressure ) related, so there is this complex inter-related physics on the pump fluid flow which sometime confuse people.
Being variable speed our 3 phase fuel pump is and having its own speed and pressure logic controlled by N118 fuel computer..... it made everything even more difficult to troubleshoot.
For the very reason explained above, I wanted to cheat the N118 pressure sensor data just to see , how much flow can my pump actually make ?
Too bad my signal generator for the cheat got lost in the shipment from China to Indonesia.

CaliBenzDriver

> New pump and filter installed but pressure still deeps during acceleration.

Running a Xentry is sort of a mixed blessing, now you can really see every details that are wrong with these good looking cars.
​​​​​​The wiring of noisy 3-Ph pump mixed with CAN & DC lines, the variable power supply, the extended GND line are amazing.
​​​​​​

You know how alternator output is lowered during acceleration.... disconnect the ALT-LIN connector to see if that causes your poor LPFP regulation issue.

Tutzi

I have now removed the Hella filter. Unfortunately the valve does not fit. I have attached an image. I put everything back together. Then I looked at the pressure value of the two sensors in the removed state. They really indicate absolute pressure. MB 1.1 and Hella 0.9
I made the two videos shortly after the first start. I will drive in the next days an look, if the mistake come again.




@CaliBenzDriver Do you think that the slight fluctuation in voltage could be a problem? On my old C3 I noticed that the displayed battery voltage jumps sometimes a little bit. I have this at engine off, too...12,9V to 12,5V

CaliBenzDriver

The new pressure sensor is good,
The new pump is good,
The new filter is good,
I don't mean to interfere... just keep in mind power supply issues when you run out of working solutions.

("little drop"... big troubles ?
The battery sensor voltage displayed by instrument cluster is greater than what is supplying LPFP through Prefuse relay, wiring and R-SAM when ALT goes off-line.
That high impedance power supply is helping LPFP PWM create taller spikes from higher currents.
The sloppy wiring drives these spikes into the rear wiring harness and R-SAM with fuel gauge sensor).

Long story short: you want ALT inline not in standby.

S-Prihadi

I believe the fuel pump is as-is and not a new one.
If indeed electrical also the culprit or part of the culprit....dang, more work for Tutzi

Tutzi

@CaliBenzDriver - this mistake came first when the filter was changed. the old pump was still there. After this i changed the pump.

@S-Prihadi - i bought the fuel pump directly by mercedes-benz. manufacturing date 2021. I must think that the pump is not the mistake, cause below.

@CaliBenzDriver - i know that mercedes has contacting problems in the plugs over all modells. I saw that in some Tips docs. But my car has no mistakes that could explain that. Should put in an voltmeter in the power supply of N118 and monitor it while driving? I could loosen the plugs on Sam-R and so on- that should bring at least a short time change.

I don't understand what you mean exactly
"("little drop"... big troubles ?
The battery sensor voltage displayed by instrument cluster is greater than what is supplying LPFP through Prefuse relay, wiring and R-SAM when ALT goes off-line.
That high impedance power supply is helping LPFP PWM create taller spikes from higher currents.
The sloppy wiring drives these spikes into the rear wiring harness and R-SAM with fuel gauge sensor).
Long story short: you want ALT inline not in standby."

This week i have not so much time, for the car, but i will make drive, to test it, after the work yesterday. Maybe i didn't do something right ,first time i installed the Hella Filter. Next step i will check the power supply of the Sam-R and N118 in operation in comparison to battery voltage..

Do you have some other tipps

S-Prihadi

Tutzi,
If your pump is new ...its nice then.
Your fuel filter is still the prime suspect now.

Our cars have "smart" ( stupid if for me ) charging which will YoYo the voltage from below minimum of 12.7V to 14V.
Under 12.7V is discharged, and that is done on purpose by the engine computer in the name of savings C02 emission...LOL.
Basically your battery is never 100% full, at best 80%.

If you take a look at the autopsy I did on my old fuel filter , there are a few parameters which can cause your fuel filter to get low pressure.
01. The regulator valve/overflow we discussed.

02. There is another baby sized valve at the input of the fuel pump, you can't access it. << if the spring is too stiif, it may reduce pressure into fuel filter.

03. The suction jet valve. You need to read my explanation how it works on that fuel filter change thread.
This suction jet valve is delicate balance. Basically your volume and pressure into the fuel filter is being shared by the suction jet valve to send fuel back from LEFT side of fuel tank to RIGHT side of fuel tank where the pump is at.

Questions :
AA> The Hella fuel filter , does it come with the 2 hoses ? This hose if it is loose at the filter input, you loose fuel flow and pressure too.
BB> How much in Germany they charge you for original fuel pump and filter ?

Tutzi

Hello,

yesterday i looked for the voltage-data in the battery-sensor and in the sam-r.

Voltmeter: 12,11 volt
Battery-Sensor: 12,20volt
Sam-R: kl.30 12,18volt kl. 30g 12,14volt

I think that is okay, i have not a high quality voltmeter and a differrence up to 0,5volt is not a problem according mercedes. Cause of the low battery voltage i connected my charger, but that cannot provide suffcient support an ignition on..

I think there is no problem. All in all i must drive the car at the weekend and must look if the mistake still occurs.

The pump costs in germany roundabout 520 Euro (8112175,40 Rupiah). The filter i don't know exactly, but i think roundabout 393 Euro (6155060,50 Rupiah) minimum. Much moneyfor a plausibility error ;-)

When i had the filter outside again, i also thought to check the 2 hoses. I thought of a loosen hose,too. But i can't see / feel something strange. ??? After assembly the filter also had a noise less compered to before. But i won't let that get me "hot"as long as i haven't driven the car ;-)

CaliBenzDriver

@Tutzi realize that 12.1... 12.2v is bad news with engine ON but not so bad with just ignition-ON (engine Off)

So to make sense of what your are measuring, you have to pay close attention under which conditions you're measuring what.

Normally 12.2 resting voltage is a low charge level. The okay range starts at 12.6V and up to 14.9V whith engine running.

Let me suggest we focus on your core problem: low fuel pressure during accelerations, right?
Look at the car voltage during the acceleration periods. Display the battery voltage on the maintenance menu. You will see voltage drop during accelerations, yes ?
That is your link between pressure drop and voltage drop.
In some bad cars the alternator goes off-line and available voltage plummets towards 12.0V 😳

Tutzi

Until the beginning of the year i had the P008700 error in the n3/10 unit with engine stutters at acceleration. After this i changed the fuel filter and since this momemt i had the P254000 error in the n118 unit. The other mistake do not appear again....and i had several freeway "flights" ;-)

Look at Post 26 there is the error log with freeze frame data. I tell it s-prihadi,too...this mistake appears when the car is "coasting" ( like going dowhill and accelerator not pushed down ) .

CaliBenzDriver

I read through your collection of pdf screen captures under post #26.

I now understand your fault does not happen during acceleration but as you said rather decelerations or coasting down hill conditions, right?


LPFP sensor error
Is this the DTC causing what you want to fix ?
The way I understand that message is "the sensor circuit is telling lies to FP controller"

To me this means the signal is not too high, not too low, not shorted to Vcc/GND. So the integrity of both wiring and sensor is OK.

So what's wrong then ??
High level of noise with low signal cause glitches that are picked up as meaningful until a DTC is produced.

CaliBenzDriver

LPFP rewiring enhancements

This is currently what I've done to mitigate my pump noise:
- separate control / power harnesses
- short additional power GND wire
- twisted pump phase wires
- RF-choke on positive feed

Less electrical noise for better:
- SAM coms... (No yoyo!)
- Fuel gauges to R-SAM
- Pressure sensor to pump module

S-Prihadi

So.... any update ?

Tutzi

Hello,

sorry for the long break, but i wanted to finish the work first before i write again. Short and sweet...i didn't think the wiring is the problem, cause i check them including the connectors and in addition the error wasn't there before i changed the filter. So i looked deep in my piggy bank ;-) and bought a new Mercedes-Benz Filter A2184700994. Much money, but the result...the car is happy :-D . The error came safely every short testdrive. Yesterday i got the filter and i directly changed him. Today the first drive to work was flawless. After work the testdrive on highway with topspeed and much cruising was flawless too. So i can say that the error disappeared. Tomorrow i will contact the seller from the Hella filter for a refund.

If i have time and inclination, i will drive again and make a video to see what the difference is now.

Here some pictures after the testdrive tonight...

S-Prihadi

Very good news , thank you
Take this as a learning adventure.
So the fuel controller N118 does have its own pressure table and probably it includes amperage and voltage parameters, hence it can detect that the
Hella fuel filter is not behaving like the original MB one and N118 flag a DTC.

From what I see and have indicated to you is, the Hella produce lower fuel pressure compared to original one.

Tutzi

In comparison the new mb filter to the new Hella filter i noticed a noise from the Hella filter which the mb filter doesn't do. Wether the hella filter was defective from the beginning, or simply doesn't fit?...i will not find out. But based on this thread, i see generally more a problem with the aftermarket filter which do not fit one hundred percent. 'As driver you will not noticed this problem as long as you not look in the error memory of the car...