MB C Class W204 Estate in tank fuel pump/sender.

[Alex1989]

I have fixed another om651 issue in the past with the same fuel rush noise.

The oxygen sensors are detecting too little oxygen in the exhaust and the fuel pump control module is adding more fuel than normal to sustain the proper air/fuel mixture.

In this case was a bad egr diverter vacumm actuator and the egr valve was not closing shut.

And the car had only 1 fault code 0629 - the output of the fuel pump (fuel pump control unit)

The car was running like new after cleaning the egr.

Hope this helps if the it happens again.

 

[explorer121]

I have fixed another om651 issue in the past with the same fuel rush noise.

The oxygen sensors are detecting too little oxygen in the exhaust and the fuel pump control module is adding more fuel than normal to sustain the proper air/fuel mixture.

In this case was a bad egr diverter vacumm actuator and the egr valve was not closing shut.

And the car had only 1 fault code 0629 - the output of the fuel pump (fuel pump control unit)

The car was running like new after cleaning the egr.

Hope this helps if the it happens again.

Hi,
interesting reading your post. I looked at the EGR this weekend, or what I thought it was but I could only see the actuator. It was not like my previous Merc with two bolts and twist to remove. On the OM651 engine it seems a bit daunting ? Have you ever removed one ?
Any advice much appreciated.

 

[Alex1989]

You have the model with the EGR cooler on the right side of the engine.

If you don't have a car lift that job can take up to 3h as the egr it's bolted on the back of the engine. The actual egr motor it's under the assembly and the vaccum valve it's at the top.

What i recomend it's to clean your MAF sensor located on the airbox and clean the MAP sensor located on the intake manifold under the EGR.
These two sensors create a lot a fueling ratio issues.
Use specific cleaners to clean them as you can damage them and leave the to air dry for 30min before installing them again.

Hopefully this will sort your issue.

 

[Alex1989]

This it's the back side of the EGR.
Verry dificult access to bolts and brackets. The most dificult bolt to remove it's the bottom bolt where it's connected to the engine.

 

[Rick449]

Hi do you have any tips on getting the locking ring off the sender unit?

 

[explorer121]

Hi do you have any tips on getting the locking ring off the sender unit?

Hi,
i'm presuming you mean the two sender units under the back seat in the fuel tank. If so make sure yoiur tank is no more than a quarter full or less then i used a large flat head srewdiver and wooden mallet and tapped the ring anticlockwise till it released. It has to release from a groove in the metal ring and must be locked in when putting back.

 

[RotaryRE]

Hi explorer121. I can confirm that you're not the only one in the world with this problem as i have the same problem exactly and the sound!!
I am due to see my local Mercedes tech next week for another issue (cracked inlet manifold YAY!!!) however this gurgling, syphoning noise has done my head in and was going to have him look at it. He did mention to be previously that it sounds like the pump may be on it's way out however after reading this discussion, i am now thinking it might not be the pump or sender as you have stated you replaced the leak off pipes and the noise disappeared.
Excuse my lack of knowledge in this area however what leak off pipes are we talking about here? Are the the two pipes shown in the photo you posted at the beginning of this thread?
I would appreciate a response on this one. Saves me replacing the pump and pick-up etc. Thanks.

 

[grober]

Refers to ford but principle is the same.
Leak off pipes - Diesel Injection Pumps

here they are in the OM651- the black pipes with the blue writing leading from the injectors [ low pressure] as opposed to the silver metal supply pipes from the fuel rail [ high pressure]

 

[explorer121]

Hi explorer121. I can confirm that you're not the only one in the world with this problem as i have the same problem exactly and the sound!!
I am due to see my local Mercedes tech next week for another issue (cracked inlet manifold YAY!!!) however this gurgling, syphoning noise has done my head in and was going to have him look at it. He did mention to be previously that it sounds like the pump may be on it's way out however after reading this discussion, i am now thinking it might not be the pump or sender as you have stated you replaced the leak off pipes and the noise disappeared.
Excuse my lack of knowledge in this area however what leak off pipes are we talking about here? Are the the two pipes shown in the photo you posted at the beginning of this thread?
I would appreciate a response on this one. Saves me replacing the pump and pick-up etc. Thanks.

Perfect reply from 'Grober' and great picture. The part cost me @£100 and only available from OEM suppliers.

 

[RotaryRE]

Legend, thanks Grober and explorer121 and agreed, picture is perfect. I’ll pass on the info to my Merc tech and have him replace them before bothering with the pump and pick up next week and see how that goes. I’ll post with an update once done. Thanks again. Much appreciated.

 

[explorer121]

View attachment 85633

Legend, thanks Grober and explorer121 and agreed, picture is perfect. I’ll pass on the info to my Merc tech and have him replace them before bothering with the pump and pick up next week and see how that goes. I’ll post with an update once done. Thanks again. Much appreciated.

Legend, thanks Grober and explorer121 and agreed, picture is perfect. I’ll pass on the info to my Merc tech and have him replace them before bothering with the pump and pick up next week and see how that goes. I’ll post with an update once done. Thanks again. Much appreciated.

Mercedes-Benz OM651 Injector Leak-Off Pipe P/N A651 070 63 81
Suitable For OM651 Mercedes Engines, but do check with reg no or VIN.

 

[RotaryRE]

Thanks again for the further info explorer121. Still find it odd that the leak off pipes are the cause given the burbling sound is coming from the back of the car however is the cheaper option to begin with and also that it was the fix for you.

 

[explorer121]

Me to, but that was the cure. Have a look at this You are being redirected...

 

[RotaryRE]

Thanks explorer121. It’s booked in so will update in a few days with the result. Legend.
Thanks again.

 

[RotaryRE]

Hi explorer and grober, was just looking over the images you both sent me just to get a better understanding before I see my tech tomorrow and the images look different from what grober has shown vs explorer121.
Grobers image doesn’t have the T hose in the middle leading down to the metal pipe and believe. The image grober posted just shows a straight black hose (with blue writing). Just making sure it’s the right one. Guessing the tech will know anyway right? Well, let’s hope so haha.

 

[explorer121]

Hi explorer and grober, was just looking over the images you both sent me just to get a better understanding before I see my tech tomorrow and the images look different from what grober has shown vs explorer121.
Grobers image doesn’t have the T hose in the middle leading down to the metal pipe and believe. The image grober posted just shows a straight black hose (with blue writing). Just making sure it’s the right one. Guessing the tech will know anyway right? Well, let’s hope so haha.

Hi, yes two different images but the one on Grober's image is most likely. Either way your tech will see the part number on the black hose and just order it from there. Be interested to see how you get on. Am away for a week so will catch up on return.

 

[grober]

There are variations on the "plumbing" but using your vin/engine number will make sure you get the correct part
FUEL FILTER, LINES MERCEDES C-KLASSE [Car] [CHASSIS] (EUROPA)

 

[explorer121]

Hi explorer and grober, was just looking over the images you both sent me just to get a better understanding before I see my tech tomorrow and the images look different from what grober has shown vs explorer121.
Grobers image doesn’t have the T hose in the middle leading down to the metal pipe and believe. The image grober posted just shows a straight black hose (with blue writing). Just making sure it’s the right one. Guessing the tech will know anyway right? Well, let’s hope so haha.

Hi, any update ? Curious to see how you got on.

 

[RotaryRE]

Hi Explorer121, apologies for not posting. I had the inlet manifold repaired the other week however the leak off pipe hadn't arrived in time so am due to take the car back to have it fitted.
Enjoying some boost now though as the car was in safe made / limp mode due to the cracked manifold.
I should hopefully have the leak off pipe done in a week or so and will post with the results.

 

[Shazzyx]

Hi Explorer121, apologies for not posting. I had the inlet manifold repaired the other week however the leak off pipe hadn't arrived in time so am due to take the car back to have it fitted.
Enjoying some boost now though as the car was in safe made / limp mode due to the cracked manifold.
I should hopefully have the leak off pipe done in a week or so and will post with the results.

Hey, so i have the exact same issue and was wondering if you found the fix, did the return pipes work or was it something else