Long shot - need help with Mercedes

[DriveHard]

I have had this posted to two different Mercedes forums for several days now with ZERO response. Just going to post it on here in a long shot someone on board could help me out. I have a 2013 ML350 with the 3.5L direct injected M276 engine with ~67,000 miles. This is my wife's daily. Here are my symptoms... Round 1: I started getting long crank times to start the car. It would always start, but just took much longer than normal. Ran well...but mileage started degrading. My wife was on her way home from work and car started misfiring badly. No power, engine light on. She was only 2 miles from home so I asked her to limp it home on the shoulder. Pull the codes...lots of misfires, on multiple cylinders. Cylinder 2 and 4 stood out. Also had code P008992 "The pressure regulating valve has a malfunction. The function or the instruction is faulty" Replaced all 6 plugs and coils. Plug on cylinder 2 was totally black. Plug on cylinder 4 was about half as black as cylinder 2, but not normal. The remaining 4 plugs looked fine. Car ran great, I took her out for a good old Italian tune up...purring like a kitten. Wife and I took the car out yesterday...started having extended cranks again. This is less than 50 miles after the plugs/coils. I also was watching the fuel economy, and it seemed much worse than normal. Wife took the car out this morning...had the same problem. Strong mis-fires, but she was in town and limped home. I went out to pull codes this afternoon... Misfires on 4, 5, 6...and P008992 "The pressure regulating valve has a malfunction. The function or the instruction is faulty" I clear codes and start it up and she purrs like a kitten again. Odd. Ok...still a newb to MB, but not to cars or engines. I am guessing this is a pressure regulating valve that is controlling cam phase? Can anybody help? A google search for the code turns up almost nothing... Please help me get my bride back behind the wheel of her Benz before she wants her Beemer back. Thank you!!!!!!!!!

 

[nthach]

There may be some MB-specific codes your OBD-II scanner isn't picking up - most scanners can pick up on the OEM-specific codes but not all and I don't think there's a federal regulation that dictates an aftermarket scanner needs to pickup anything that isn't a P0xxx code. This might be the time to take the car into an indie Mercedes tech, but since fuel systems are covered under emission systems warranty, I'd go to the dealer. I'm not sure how generous the federal warranty is. GDI systems do work similarly to a common rail diesel system, high-pressure fuel pump driven off a cam and high-pressure sensors. My suspicions is a "fluttery" high-pressure pump not working at proper PSI to feed the injectors, wiring issue or the sensor. I'd look for an OEM-specific code before going further.

 

[FowVay]

Have you checked the fuel rail and fuel pressure regulator? It sounds like you're misfueling for some reason. Replacing the plugs helped with the symptom but didn't cure the cough. That particular DTC doesn't appear to be a valid DTC either. P0089/P0092 seem more plausible. Check the fuel filter, fuel pump, or pressure regulator.

 

[knerml]

Check battery voltage. It might be low enough that a sensor is giving false data. Had similar problem with my Kia. Charged battery and everything is fine.

 

[DriveHard]

Originally Posted By: nthach

There may be some MB-specific codes your OBD-II scanner isn't picking up - most scanners can pick up on the OEM-specific codes but not all and I don't think there's a federal regulation that dictates an aftermarket scanner needs to pickup anything that isn't a P0xxx code. This might be the time to take the car into an indie Mercedes tech, but since fuel systems are covered under emission systems warranty, I'd go to the dealer. I'm not sure how generous the federal warranty is. GDI systems do work similarly to a common rail diesel system, high-pressure fuel pump driven off a cam and high-pressure sensors. My suspicions is a "fluttery" high-pressure pump not working at proper PSI to feed the injectors, wiring issue or the sensor. I'd look for an OEM-specific code before going further.

This is a Mercedes Benz specific code reader...there are no additional codes. The code P008992 appears to be a MB specific code of which I can't find a single detail on. The other 4 codes were the misfire on 4, 5, 6, and a code for general misfire. If it were fuel pressure...wouldn't it effect both banks?

 

[Ethan1]

It's not manufacturer-specific, it's "P0089-92" and it's talking about the fuel pressure regulator. I can't even get a diagnostic flowchart from Mitchell, so you're gonna have to break out all the traditional fuel system testing tools plus the best scantool you can get your hands on.

 

[meep]

this reeks of a fuel pressure issue. not all systems monitor it. volvos do - it's electronically regulated - but in many designs it's a mechanical regulator either in the pump side, or in the return side if it's a circulating system. based on pretty much no data, it actually sounds like it's running lean to me. in volvos, the electronic fuel rail pressure sensor is well-known to fail. -m

 

[mightymousetech]

The long cranks suggest a faulty high pressure fuel pump or leaking injectors.

 

[JHZR2]

Im sorry, what part of pressure regulating valve would make you change plugs and coils? It just doenst make sense to me personally... Id be looking at a DI fuel pump or something with variable valve timing. Do you have access to MB specific codes on that scanner? Have you asked at PeachParts?

 

[Dadillac]

Originally Posted By: knerml

Check battery voltage. It might be low enough that a sensor is giving false data. Had similar problem with my Kia. Charged battery and everything is fine.

This is where I would start. Having owned 2 Cadillacs and having 2 Lincolns in the family has taught me how vital battery voltage is to luxury vehicles. My experience is many hundreds of dollars, many many hours, only to be a failing battery. YMMV Don

 

[Astro14]

Has the battery been run down to flat? The AGM in your MB won't recover from that and will need to be replaced. Low battery voltage causes all sorts of issues.

 

[Audios]

It seems alot like an internal fault in one of the high pressure pumps. THeres usually one pump per bank, so it can affect just one bank.Its allowing pressure to bleed down while in operation, so the car isnt seeing the 3k psi it needs for correct injection. Youll probably need a high pressure pump to start, hopefully theres no cam wear issues like on the earlier Audis. Also, go in with a generic tool or switch to OBD2 to see if you can get the fuel pressure codes as a more normal P fault. My Autel can switch to generic, sometimes this helps.

 

[Astro14]

Further, your icarsoft is good, but falls well short of Mercedes OE diagnostic equipment, known as STAR (DAS, XENTRY, etc.). If you really want to know what's going on with your MB, get someone with STAR, hook it up and have them read ALL THE CODES, including all the codes missed by icarsoft. Each code in STAR will have troubleshooting steps, that you, or your garage with STAR, should follow. STAR includes the ability to energize circuits and devices, like pressure pumps, as part of the troubleshooting. When you see STAR in action, you'll know what I mean. I've got a EBay copy, from China, running on a Dell D630, through a multiplexer, and it includes everything, including all of the workshop and service information. For example, I can run the secondary coolant pump (intercooler system) from my laptop, and I can move windows and seats, to check door and seat modules. I can articulate and calibrate the suspension. The list of STAR functionality is practically endless. In the meantime, if your battery isn't strong, then you'll get all sorts of weird malfunctions, so do check that first.

 

[Ethan1]

People... it's a regular OBDII code with a sub-code. And when the battery dies on a car like this, it generally sets <span style="font-style: italic">dozens</span> of codes. Smh...

 

[Astro14]

Originally Posted By: Ethan1

People... it's a regular OBDII code with a sub-code. And when the battery dies on a car like this, it generally sets dozens of codes. Smh...

Regular OBD-II codes are worthless in this case.

 

[Ethan1]

You can only work with the codes you have. It has a generic OBDII code. It does not have any manufacturer-specific engine codes, or the scan tool would at least show the code number.

 

[spk2000]

Might be a long shot but my Grand Marquis which is completely different but had similar symptoms led me to Mass Air Flow sensor being dirty as a possibility. Was starting slow and hard would sputter when I tried to take off and under acceleration would misfire. Less than $10 for a can of CRC MAF sensor cleaner. Mine was located just behind the air filter. Never did this before but sprayed it from both sides and wow what a difference. Car starts very easy and idles great now. Smokes the tires at takeoff. Hard to keep it from spinning in the rain as it does not have traction control. I was close to trading the car off as it really ran bad but now I want to drive it again.

 

[DriveHard]

Thank you for all the replies! I will do my best to add details and answer questions. The battery is great...and not the cause at all. The car cranks very quickly, and has no hint at all that the battery is bad. I changed the coils and plugs because it was due for new plugs at 60,000 miles and I had not preformed the service yet. I previously owned a BMW x3 that ate coils every 30,000 to 40,000 miles...so figured it was possible a similar German design would do the same. I used genuine OEM parts for both plugs and coils. The more responses I read and the more I think about it, the more I agree that it seems like a high pressure fuel pump issue. There is only one for the engine, I believe it is run off the right bank. Still puzzles me why only one bank of cylinders is showing the misfire. I need to go hook up again and pull codes from the latest round of trouble...so maybe that will show different?

 

[flanso]

On some vehicles, there is a pressure regulating device on the fuel rail that maintains fuel pressure in the rail when the vehicle is not running. When this check valve device fails, crank times increase while the fuel pump works to restore pressure in the rail.

 

[DriveHard]

Ok...update MAN I HATE INTERMITTENT FAULTS!!! I went home and pulled codes. I got the same code P008992, but no misfire codes this time. I cleared the code again, then started it up. She started right up and ran great. I let it idle for about 15-20 minutes. During that time I was revving it up occasionally and would hold it at ~2000 rpm for 30 seconds or so from time to time. The whole time she totally ran great. I then drove it about 25 to 30 miles. Fuel economy was back to where it should be, and power was great. I drove it at 4500 rpm for about 6 to 8 miles as well, along with several full throttle runs. I then shut it down and let it sit, then tried to start it again and it started perfect. I hooked up the scanner again, and no codes on anything. So...I guess I start driving it again until I can capture a fault again. Right now my gut is telling me I have something going on in the fuel pressure regulator that is intermittent, and made worse with heat. Every time the car sits for a long period of time and I come back to it, it starts right up. This tells me nothing is "draining down" or leaking...but instead I am thinking it is over-pressure and delivering too much fuel. When I get a long hard start you can always smell fuel after she finally catches. It appears the high pressure fuel pressure control is built into the pump and cannot be replaced on its own. HPFP runs about $500 and is located on the back of the right bank. I have not been able to actually find it on the engine, or even see a picture showing where it is located, but I am guessing I will be replacing this beast down the road shortly. Any more thoughts?