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CDI Fuel Pressure Regulator / Y74

38K views 41 replies 10 participants last post by  DieselBound 
#1 ·
2005 E320 CDI, i've got an idling misfire/ missing issue that almost feels like fuel starvation to the injectors that I've traced back to either the fuel pressure regulator (Y74) or quantity control valve(Y94).

Y74 is the screw in style mounted on the back of the rail, shown in the attachment below. I've heard that this valve isn't changeable on the rail?! That you have to change the whole rail?! That cant be true. The valve itself is readily available. Its not like the rail is cast around the valve?! It threads in! Is there any truth to this? Or is it hogwash?

P/N for the pressure regulator is 648 070 00 46
 

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#2 ·
It is changeable. It's just way after sales are f**ing with customers, by forbidden selling regulator part only. It's not long time ago you actually could buy regulator individually. Just search part number, you may even found new one, or then try second hand part...
 
#3 ·
The valve is readily available! all your online parts sales places sell both the MB branded part and the bosch part. i just remember reading about people that have changed the valve and had problems and needed to replace the whole rail.
 
#5 ·
Sorry for reviving an old thread but Rossafuss; did you ever end up replacing this valve or was this part of the swirl flap issue? I am having some serious issues with my car and it is not throwing any codes (OBD or Benz). Seems like an intermittent TPS issue or something. Have to log some more miles but researching has begun. Thanks.
 
#6 ·
No need to be sorry, this is what forums are for!

I did end up changing the valve. But I'm not sure whether this problem was related to the misfiring issue that end up being swirl flaps. I ended up changing hundreds of dollars of parts before I ended up finding the actual solution, which ended up being free. ?

The valve itself has an o-ring on it that forms a critical seal for proper rail pressure regulation, I recommend changing that o-ring before you end up changing the whole valve.
 
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#18 ·
No need to be sorry, this is what forums are for! I did end up changing the valve. But I'm not sure whether this problem was related to the misfiring issue that end up being swirl flaps. I ended up changing hundreds of dollars of parts before I ended up finding the actual solution, which ended up being free. ? The valve itself has an o-ring on it that forms a critical seal for proper rail pressure regulation, I recommend changing that o-ring before you end up changing the whole valve.
Hey Rossafuss, I'm re-reviving this thread 😂 I have a loss of power on my w211.007 220cdi, limp mode on to max 3000rpm, check engine light on, 22AO Y74 (Pressure regulating valve, 2373 Check injector injection adjustment) codes come up. Y74 seems fine from outside (haven't opened anything yet). I was wondering if you have a part number or a picture or something for the o-ring?
 
#7 · (Edited)
Thank you for the reply. Where would I be without forums?...I don't want to even think about it.

The issue I am having is exactly described in post #2: https://www.benzworld.org/forums/w211-e-class/1463287-w211-e220-cdi-lack-power-help.html

The solution was new swirl servo (not going to replace) & clean intake. You think intake buildup would be the cause of this issue?! I also have a strange turbo noise but absolutely no codes. I took a video but not much help until I figure out how to share.
 
#9 ·
The post you referenced mentioned a loss of boost pressure, is that what you're experincing?
If so, remove BOTH of your rubber turbo/intercooler hoses and check them for cracks and gashes, as well as blown out o-rings on the ends It's actually very common for these cars to leak around the o-rings, as well as the rubber hoses to break down from oil contamination and bust open.
 
#11 ·
My car makes that fuf fuf fuf noise all the time, it's called compressor backlash, it's common after a sudden increase in manifold pressure and a decrease in turbine pressure, its essentially turbulence
 
#15 ·
Thank you from me as well. My cummins does it before a quick shift and it's called (by some) turbo "bark". It is much louder and violent but just making sure. Next question: Is this a normal sound for our HPPs?



I posted this on my long saga of repairs thread but it is fuel related. Still getting a brief cutoff at 2200rpm but pulls hard before & after. No codes but data logging via Torque Pro starting today.
 
#20 ·
Hey Konigstiger, thank you for the reply. 😊
Do you think there's one somewhere between the 'nuts' that connect Y74 to the rail? I guess I will have a better understanding once I open it.
Also, it looks like I'm missing an e10 bolt (no5 in the picture you're attaching, between the two no35's. Do you thinks it indicates to someone medling with it before?)
For better understanding, car is E200cdi (136hp originally) optimised to 200hp, 138.000km. I don't have any reasons to be suspicious about the optimising I think, I did it over a year ago (car had ish 100.000 km), no problems, until this of course, at a place where thousands of people have done optimising to their cars without complaints, and same company helped before optimising the MB with another car I had with programming an abs module. So I'm leaning to this just being a normal MB issue. I'm going to open it tomorrow I think to have a look at the whole intake manifold, servo motor, swirl flaps and give you guys an update but it would be amazing if I could get a heads up and save some time. 🙏😊
 
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