CapsFanBen

Has anyone done this? How difficult is it? I have seen a video of the intake manifold removal which seems like a pain because of all the things to detach, but it doesn't seem that difficult if you have patience lol. However, I can't seem to find a video specifically regarding the fuel rail pressure sensor. Once you get access to the sensor, can you just remove it and install the new one, or is it move involved than that? Will I need any new gaskets? Is there a proper torque value?

Siegmann

It's easy to get to; just need to relieve rail pressure first. Can't say what the tq value is, but someone with WIS will probably chime in.

CapsFanBen

Re the rail pressure...yeah I read that about dealing with the rail generally but wasn't sure it was necessary for this project. I saw a post that scared me a little because of the pressures involved! Is there a walkthrough of how to relieve the pressure? It sounds like you also have to do a bleed after you put it back together?

And what is WIS? A service manual? I am trying to fix my mother's car and avoid my dad getting gouged by a mechanic lol. I'm a BMW E46 guy myself--so many walkthroughs for that car!

The E350 is throwing both a rich and a lean code and in the past it has thrown a code specifically for the fuel rail pressure sensor. Of course I know that replacing it may not fix things, but I figure it's worth a shot if its not too difficult of a job. Her car unfortunately suffers from the ****ty crankshaft position sensor seal (?) getting oil on the ECU, and I know that the ECU has had trouble, so it might be that it's the ECU and not simply the sensor, but I figure swapping the sensor is worth a shot because I think a new car is definitely in order over replacing the ECU.

kajtek1

How did you troubleshoot you need new sensor?
When the pressure in the rail can be in 100's thousands of psi, it is drained once you shut the engine down.
Still good idea to check with scanner what is left.
Diesel fuel doesn't compress easily, meaning all the pressure from the rail will drain in form of few drops.

CapsFanBen

What troubleshooting do you suggest? I am getting a code specifically for the sensor and rich and lean codes but only on bank 1. It is a gasoline engine--not diesel.

Siegmann

Relieving the residual pressure is simple - there's a Schrader valve on the incoming line. With the engine cool, you remove the cap, cover with a rag and slowly press down on the valve. There shouldn't be much, but it's safer than removing the sensor straight away.

I agree if you have a code for the sensor then it's best to go ahead and replace it.

WIS is factory service procedures.

CapsFanBen

Thank you. Just to confirm--it is necessary to remove the entire plastic intake manifold to get to the sensor? I took a look in the engine bay and that seemed to be the case. And--to be clear--the sensor code is intermittent. Like I said--the ECU may just be toast from this ridiculous issue with oil getting on it from bad crankcase position sensor seal, but, while MB was willing to replace the ECU on lots of these cars, my mother was not so lucky. I figure swap the sensor and hope it fixes the problem or else it's new car time because it would be foolish to replace the ECU.

S-Prihadi

I assume ur engine is GDI ? Yes.
My engine is the 3.0 TT M276.820, but it is very similar with the M276 3.5 NA

Here............. https://mbworld.org/forums/e-class-w...re-sensor.html

CapsFanBen

Thank you!!! Yes the engine is M276. Did you need to remove the entire intake manifold big black plastic piece to get to the sensor?

S-Prihadi

M276 3.5NA ......... yes u must remove that giant black intake manifold + PVC system.
Mine is a 3.0 TT is easier, much easier because my airbox is 2 units , one each bank and not like your engine.

CapsFanBen

Thank you! Does the system need to be bled after you're done?

CapsFanBen

Also--is this a common thing to fail at 120k miles? I am trying to figure out the likelihood of this fixing the problem. The part isn't too expensive, but not excited to deal with removing that giant intake manifold lol. I have had to change the crankshaft position sensor and intake camshaft position sensor on my 2003 with 110k miles but not the fuel rail pressure sensor.

S-Prihadi

Aside from a VERY good fire extinguisher standing by, here is what you need and the DO and DONT for piezo based GDI.

01. You must have a scanner which can do bi-directional control, for activation of the LP fuel pump at the fuel tank. Most likely your LP fuel pump is already the 3 phase version and do not ever-ever try to
inject power to it manually to make it run. You will burn it. Single phase oldie fuel pump you can inject 12V and it will run, but don't ever try that on a 3 phase fuel pump.
Read here : https://mbworld.org/forums/e-class-w...er-change.html

02. Never never remove the connector to a piezzo injector/s when engine is running.
Read here : https://www.pfjones.co.uk/disconnect...s-running.html
Ignore the fact that the link is for a diesel common rail, piezzo is piezzo.

03. Never empty fuel rail by cutting fuel supply to our kind of GDI and let engine run and died till fuel starved, because the HP pump uses fuel for lubrication of its plunger/piston and running it till it dry will score it and eventually
it will be short lived or damaged. The same for starting the engine after you done with your HP fuel pressure sensor, you must FIRST prime/TURN-ON the LP fuel pump using a scanner to feed fuel to HP fuel pump and
bleed out from one of the two output pipes of HP pump towards left or/and right rail. Bleed fuel at the rail. That pipe fitting is a not a one time use ferrule, so you can leak fuel out and tighten it again.

Stay safe..............

S-Prihadi

I forgot to remind you.
Depending on your 3rd party scanner, Autel at certain firmware number for MB, when you do bidirectional fuel pump activation, the dumb-azz Autel will run LP fuel pump for like 20 seconds and CAN NOT be commanded immediate OFF.
So before you do anything, do a bidirectional test without loosening/leaking anything and go behind at the rear seat and hear if your scanner can immediate ON-OFF the LP fuel pump or it is like that dumb-azz Autel.

CapsFanBen

Thank you so much for all this great info!

So it sounds like I will need a special (expensive?) tool in order to finish this job by bleeding the fuel line. I think that may send me the direction of just having a mechanic do this job. What's the cheapest scanner I can buy that will do what I need for bleeding the fuel line?

S-Prihadi

You are in luck, under US$160 https://mbworld.org/forums/e-class-w...onal-more.html

CapsFanBen

Thanks! Now I gotta figure out if having that tool is worth it to me beyond just this job! My dad also has a Benz though (2006 S430), and I am sure he and my mother will continue to buy Benz's--although this whole thing with the ECU getting bathed in oil from a bad crankshaft position sensor sure would turn me off!!!

S-Prihadi

When u own a Benz , u must own a scanner, minimum that baby el-cheapo Launch.
It will help you save money and time and frustration. Take it like a nice dinner $$ for two.

CapsFanBen

I of course own a scanner--but just one of the cheap $20 ones that's just good for reading generic codes.

kajtek1

MB -oriented scanner will give you live data on fuel pressure.
Codes, depends on the year are more or less generic, meaning they send you into area of troubles, but not necessarily pinpoint it.
Good idea to get 2nd confirmation.
Lately Think Diag has the best reviews, when I still love my HT/AP200

CapsFanBen

I hear you. I just don't know how much use I would get out of it. However, my parents each are loyal to MB and they are not the type to buy a new car ***** nilly so maybe it is worth it!