Long shot - need help with Mercedes

[DriveHard]

Originally Posted By: Audios
Theres something going on with the fuel injection on that bank, possibly carbon buildup is starting to show its face. Ill bet if you can take a look at the back of the valves there will be buildup. The catalyst is an emissions component and should be covered under extended emissions warranty, in NJ its 8 or 9 years I think, so check the info for your state.


There is evidence that MB has solved the carbon issue by having the injection pulse while the intake valves are open and it actually sprays on the back of the open valves. There is no evidence of carbon problems on this engine that I have been able to find. Also, full throttle power is still great! It hasn't seem to lose any power through this whole thing.

 

[jeepman3071]

Originally Posted By: DriveHard
I have found an Indy shop nearby I am taking it to next...


Yeah definitely try another set of eyes with this car. Some of the Euro indy shops can be pretty good at diagnosing odd intermittent issues. The dealers these days seem like just parts swappers. If they swap a part and that doesn't fix it, they are lost until you bring it back and it doesn't run.

 

[DriveHard]

Dropped off at Phase Garage in Ames, IA this afternoon. They actually pre-read my two page description of the problem in detail and seemed excited to figure it out. I'll keep you posted.

 

[SatinSilver]

Shop looks pretty good from what I can tell:

https://www.yelp.com/biz_photos/phase-garage-ames?select=HwmXslwXerRrdEMLalmYzg

Looks like they do some pretty good detailing:

http://www.phgarage.com/

Project car:

http://www.phgarage.com/articles/12

 

[DriveHard]

Originally Posted By: SatinSilver
Shop looks pretty good from what I can tell:

https://www.yelp.com/biz_photos/phase-garage-ames?select=HwmXslwXerRrdEMLalmYzg

Looks like they do some pretty good detailing:

http://www.phgarage.com/

Project car:

http://www.phgarage.com/articles/12


Yeah, everything I could find online looked good. The shop was clean and well sorted, and the quality of cars in the parking lot when I got there was very high!

I originally had my eye on another Indy shop nearby with decent online reviews...then I stopped to talk to them...what a wreck of a shop. I would likely have parts from 3 different cars on my car after they got done with it.

 

[DriveHard]

Got a call last night...they say there are a couple bad injectors. They run ~$250 a pop. I will keep you posted.

 

[nthach]

Originally Posted By: DriveHard
Got a call last night...they say there are a couple bad injectors. They run ~$250 a pop. I will keep you posted.

That would make sense - and those are GDI injectors that do see higher pressure and combustion chamber temps at the tips.

 

[DriveHard]

Well, shop ended up spending three days with the car. Talked briefly with them yesterday. They confirm there is an issue...but they can't pinpoint it. Injectors all tested good...and fuel pressure is ok. Not quite sure what to do next. I still have this suspicion it is the high pressure fuel pump. I am going to spend a few minutes with the mechanic who did the work and see what all he tested. I still have a hunch it is the HPFP. They bolted it back together and didn't charge me a dime!!! If I ever go to a shop again this will probably be my first stop.

One detracting note...when my wife picked up the car yesterday afternoon she got lectured pretty bad about using E85 - even though MB says it is a flex fuel vehicle. I can't believe they would put out a flex fuel vehicle that was not actually flex fuel.

 

[rodinator1234]

If there has been E85 ran through the HPFP and you suspect there is damage to it, on occasion and this is out there but I've done it before. Fill the tank with regular fuel, and put a full 6oz of MMO in per 10 gallons, so if the tank is 20 gallons, put 12oz. Drive it and see if it runs fine, if it does I would bet the HPFP is not putting out consistent pressure across all the RPM range. This system is not that much different than the Ford Ecoboost system. E85 and DI engines with a HPFP do not work well together at all. Feel free to call [censored], but your cost and risk are minimal.

 

[DriveHard]

Originally Posted By: rodinator1234
If there has been E85 ran through the HPFP and you suspect there is damage to it, on occasion and this is out there but I've done it before. Fill the tank with regular fuel, and put a full 6oz of MMO in per 10 gallons, so if the tank is 20 gallons, put 12oz. Drive it and see if it runs fine, if it does I would bet the HPFP is not putting out consistent pressure across all the RPM range. This system is not that much different than the Ford Ecoboost system. E85 and DI engines with a HPFP do not work well together at all. Feel free to call [censored], but your cost and risk are minimal.


I did just that, and it did indeed improve...but not entirely eliminate the problem. I actually used TCW-3 instead of MMO, but same effect. I am calling the Indy shop later today to get a quote on installing a new HPFP. I could do it myself, but I just don't have the time recently.

 

[rodinator1234]

If you think of the fuel system similar to that of a high pressure common rail diesel, and the issues with sticktion (spelling, moment of inertia when there is a stop in the motion of the pump or the injector for a micro second from sticking)_in injectors and high pressure pumps then it makes a little more sense in a high pressure direct injected gas engine. When you have a failure of a high pressure pump, or a lack of fuel delivery over all RPM ranges and loads conditions, it causes random issues. I would no way ever run E85 in a direct injected vehicle regardless of manufactures recommendations, more than likely the HPFP is scarred a little and allowing loss of pressure at certain loads and RPM's. You could have some injector issues as well. What I suspect the MMO does in the fuel system is increase the viscosity and lubricity of the fuel allowing the pump/injectors to operate more efficiently through it's RPM/Load range there by masking/identifying the problem.

I hope you get it solved and back running good for your wife.

 

[Wolf359]

Good luck in your search for a solution. I would have figured that you had it figured out by now. Did you try the forums over at mbworld.org? There's usually a guy there, Konigstiger who is pretty good at this. Ends lots of threads with very precise information. You might want to try PM him over there, he may have just missed your thread if you posted it there. I suppose you could check a few other subforums too, sounds like this is a problem with the M276 engine and not that particular model. I'd also eliminate E85. You could try changing the downstream O2 sensor but I doubt that's your problem because that's usually just there to tell you that the cats are bad and it sounds like it's something else causing it. Downstream O2 sensor faults can also be exhaust or vacuum leaks. On that engine, you have to take off the intake manifold to change the plugs at 60k so maybe something is loose?

Also what are you using the pull the codes? Most engine/emission codes are 4 digits. If they're MB specific codes, then yeah, very hard to find any info on.

 

[rodinator1234]

The HPFP is a positive displacement pump. The fuel system relies on it delivering its precisely measured amount of fuel on each stroke, if it deviates even .1ml there will be an issue in the fuel system, the fuel pressure regulator will not be able to react fast enough. The fuel pressure regulator is slow acting, and by it's nature will maintain a higher pressure in the system than is required at all times, when a lower pressure occurs is when all sorts of random issues happen.

If for example in this particular instance of long cranking on starts in this Mercedes. If the HPFP piston hangs in the cylinder/bore and does not develop any fuel pressure the vehicle will not start. There will be a low fuel pressure code, as there is no way the ECU knows the piston in the HPFP did not make a complete stroke. By continuous cranking, through vibration the piston dislodges and resumes pumping building pressure and the vehicle starts. There is no sensor that detects stroke length or stroke completion of the HPFP, the only tattle tale or monitor of the operation of the HPFP is the pressure sensor. It either makes good pressure or it doesn't.

During operation/running condition, lets say the HPFP hangs just a second, or it lets fuel bypass the piston at a certain load/RPM range and does not deliver the amount of fuel required, one or more cylinders will not have enough fuel for complete combustion and show a misfire, it could be the same cylinder often or it could be different cylinders at different times depending on when in the rotation of the engine (firing order the deviation of fuel pressure/delivery) occurs.

E85 lacks the lubricity to properly lubricate the fuel system of a direct injected engine in my opinion. E85 is very dry, very corrosive and has probably scarred the cylinder/piston of the HPFP. HPFP also wear, and over time wear just like any other component in a vehicle. In a High Pressure Common Rail diesel, often when the high pressure pump fails, due to say, DEF being put into the fuel by the owner by mistake/on accident it not only takes out the HPFP but also all the injectors with it.

 

[DriveHard]

I have the HPFP showing up today, and an appointment with the shop tomorrow. I am asking for the old pump back so I can dissect it. I will keep you posted.

 

[rodinator1234]

Originally Posted By: DriveHard
I have the HPFP showing up today, and an appointment with the shop tomorrow. I am asking for the old pump back so I can dissect it. I will keep you posted.


Good deal, I'm hopeful you will be successful and not have any damaged injectors, and get your wife back rolling in her Benz.

 

[nthach]

Originally Posted By: rodinator1234
If you think of the fuel system similar to that of a high pressure common rail diesel, and the issues with sticktion (spelling, moment of inertia when there is a stop in the motion of the pump or the injector for a micro second from sticking)_in injectors and high pressure pumps then it makes a little more sense in a high pressure direct injected gas engine. When you have a failure of a high pressure pump, or a lack of fuel delivery over all RPM ranges and loads conditions, it causes random issues. I would no way ever run E85 in a direct injected vehicle regardless of manufactures recommendations, more than likely the HPFP is scarred a little and allowing loss of pressure at certain loads and RPM's. You could have some injector issues as well. What I suspect the MMO does in the fuel system is increase the viscosity and lubricity of the fuel allowing the pump/injectors to operate more efficiently through it's RPM/Load range there by masking/identifying the problem.

I hope you get it solved and back running good for your wife.

I would imagine that the latest generation or two of DI injectors would use materials that can cope better with ULSD as well as low-sulfur/E85 gas like more Viton or other engineering polymer for seals and stainless steel or another metal that doesn't react with alcohols or water to corrode?

 

[DriveHard]

Originally Posted By: nthach
Originally Posted By: rodinator1234
If you think of the fuel system similar to that of a high pressure common rail diesel, and the issues with sticktion (spelling, moment of inertia when there is a stop in the motion of the pump or the injector for a micro second from sticking)_in injectors and high pressure pumps then it makes a little more sense in a high pressure direct injected gas engine. When you have a failure of a high pressure pump, or a lack of fuel delivery over all RPM ranges and loads conditions, it causes random issues. I would no way ever run E85 in a direct injected vehicle regardless of manufactures recommendations, more than likely the HPFP is scarred a little and allowing loss of pressure at certain loads and RPM's. You could have some injector issues as well. What I suspect the MMO does in the fuel system is increase the viscosity and lubricity of the fuel allowing the pump/injectors to operate more efficiently through it's RPM/Load range there by masking/identifying the problem.

I hope you get it solved and back running good for your wife.

I would imagine that the latest generation or two of DI injectors would use materials that can cope better with ULSD as well as low-sulfur/E85 gas like more Viton or other engineering polymer for seals and stainless steel or another metal that doesn't react with alcohols or water to corrode?


There are two versions of the exact same pump for MB. One pump is ~$40 more expensive and is E85 capable. I imagine the difference is just that...an improvement in materials to deal with E85.

 

[rodinator1234]

Is there any other manufacturer besides Mercedes Benz, that sells (advertises) a direct injected E85 compatible vehicle? All of the Ford Ecoboost's direct injected are not E85 compatible, nothing General Motors sells that's direct injected is E85 compatible. All E85 compatible vehicles that I'm aware of are all indirect injected.

If I'm wrong, please by all means correct me.

 

[DoubleWasp]

We dealt with a 335i that had issues due to the HPFP. When we went to remove it, we discovered the drive key and pump had separated. How that car was still running and driving, we will never know.

335i's are well regarded for their HPFP issues.

 

[rodinator1234]

The reason for E85 incompatibility is the fixed displacement of the HPFP and the higher fuel volume required for E85. The HPFP will displace X amount of fluid per stroke, and the fuel pressure regulator maintains a constant pressure in the fuel rail for proper distribution to the cylinders based on a known amount of fuel. E85 contains 2/3 the enegery of E10 (basically) so the HPFP has to deliver 1/3 more fuel to achieve the same fuel pressure in the rail on E85. The injectors are going to fire and compensate for that loss of energy in the E85 to maintain a static AFR, so there duty cycle will increase. The HPFP being a fixed displacement, can not increase it's stroke nor the speed of its stroke to compensate for the increased demand required by engine needing more fuel. Usually with dedicated tuning, E30 is the most you can get out of a direct injected engine and maintain a safe AFR and running condition.