Shawn K

Hi,I have bought 2003 Mercedes C240 with 130,000 KM, and Sedan. It is my first experience with Mercedes , feels so good driving Mercedes but I have got few problems and I need your help, I am getting system too lean bank 1 , system too lean bank 2 error, I put new wires and spark plugs, I took off MAF Sensor and I washed and clean it with MAF Sensor Cleaner, but some times when I am driving I feel the car loose power, some times knocking noise from engine, and hard to start the car every morning ,
Also the gas gauge does not show correctly , it was showing 1/4 instead of showing empty, and I did not know it, It put me in problem and I ran out the gas in middle of highway , I did few research and spent $, I am wondering is this fuel pump or fuel filter or MAF sensor problem or any thing else,
I am not mechanic , please let me know if you know or suggest any thing,
Your help really appreciate,

Bearded

System bank too lean or Rick could easily be caused by a air leak, typical its the $12 hose on the M271 engines especially when there is a loss of power, on my car onces I replaced that hose there was a HUGE increase of power.

As for your fuel situation, it could be a sensor thats connected to the fuel pump which is faulty that tells the ECU how much fuel is in the fuel tank. TO check if your fuel pump or fuel filter needs changing, check the pressure on the fuel rail and check how much psi/par on m271 engines its 55psi

Shawn K

Thank you for your reply, where is this hose located?
I am hearing small vacuum noise from top driver side engine and also there is one part which is knocking , I attached the picture for that area where I am hearing vacuum noise,

RCPDesigns

The part you have circled in red is the purge valve and it knocks/clicks. I believe it is quite normal for it do so.

Per the $12 hose, this probably is your starting/performance problem. Check this thread

https://mbworld.org/forums/c-class-w...placement.html

samaritrey

Since you have a c240 its not the $12 hose as you have the m112 v6 engine. And yes the purge valve is not your issue that is completely normal.

Fuel pressure would be a good place to start as well as unplugging the maf and see if the startup is better. The car uses a default map and if it doesn't have the startup issue you found your problem.

RCPDesigns

Yeah, my bad. I looked to see what car you had but I looked at Bearded. Quite a brain fart considering the TITLE of your post has your car type. Oh my I'm getting old...

Shawn K

No Problem, thank you for your reply,
Last week I ordered MAF sensor and then we replaced new one and we went to test drive
but problem was exists and then we tried the another new one which I have on my Car,When I replaced the new MAF Sensor I start the car but It took a time to start again , I went for test drive and nothing changed, Car was stalling again, I took the car for test drive again and I put the car in pressure and the car drove nice after 10 minutes driving in high RPM , right now I am thinking for fuel filter , May be that one is faulty because the car takes long time to start when the engine is cold,I have P0171 and P0174 error code on car, system is too lean, too much air or little gas, ...
I could not hear any vacuum noise from engine, It really costs for me to test it.

RCPDesigns

samaritrey (and others) mentioned the fuel pressure and I think this might be a good next step for you. The AutoZone near you should lend out the tool you need. Hook it up to the fuel rail and monitor the pressure.

Shawn K

As I said, one of my fuel tank is faulty, I have 1/4 Gas in tank but I can not start the car, I think the passenger side tank cant siphon enough gas so every time the gas runs out and all dirt goes to fuel filter, I have to change the fuel sending unit and fuel filter, I will let you know the result,but I dont know if there is any fuel pump in fuel sending unit(?).

kgs

Just suffered the running out of fuel issue at a quarter tank on the C240. Sender side of tank at a quarter while pump side completely dry.

Fuel pressure was good at 55PSI, so believe it was a low fuel pump flow rate causing the venturi effect not to work on the sender side.

Got a used sender and pump from a C230 and no further problems + engine way more responsive.

Sender unit is side with the external fuel supply and return lines, and fuel pump side has no external connections !

IlkosMB

So I have kind of the same problem hard start in the morning, and my Car stalled yesterday.
I year ago I replace the crankshaft position sensor.
I unplugged the MAF this morning and the car started without problem.
According to your quote then the MAF is bad, as I checked the fuel pressure is good