RubiJeeper

Hello, 1st post here. My wife has a 2011 E350 Sedan 4matic with 3.5L V6 M272 (Model 212.087) without pzev. It has 90k miles, which has been trouble fee so far. The other day I tried to start it after the car sat for 3 days and it would not start. The temperatures have been high of 50F and low of 30F. The battery voltage is fine, and the car is turning over perfectly., but it is not starting up. I tried this several times, until during one of the starting tries, it sounded like it wanted to fire up. After a few more times, I was finally able to get it to start. I began to back it out of the garage to take it for a test spin, and then the check engine light came on and it felt like it was not running on all cylinders, so I pulled it back in to the garage and parked it. I do not have a OBD2 scanner so I was not able to check the code. A few hours later I tried to start it up again, and it fired up like normal, and I took it for a drive, and everything seemed back to normal, with no codes showing. I tried to start it again the next day, and it started normally again.

Now, my wife is afraid that she is going to get stuck somewhere if this happens again, which I do not blame her. To me, this sounds like a fuel pressure issue, like somehow it lost fuel pressure while it sat those few days (never had this happen before). I am not familiar with the E350 and the common issues that are normally found on these cars, so I am reaching out to you guys to help point me in the right direction.

First, does this sound like a fuel pressure issue? If it is, what would be the first thing I should be looking at? Looking at part diagrams online, the fuel tank appears to have two different fuel pumps, a left and a right. The left being the Fuel Sender Unit (part # 204-470-44-94) and the right being the Fuel Pump Assembly (part# 204-470-07-94). I understand that it could be either of these causing the issues, but would it more likely to be the Left sending unit to be causing this? Is there a separate fuel filter somewhere? Also, if this does NOT sound like a fuel issue, please let me know!!

Thanks in advance.

pierrejoliat

Well, you need to borrow or purchase a code scanner, I have the ICarsoft MB2 and it works great, cheaper than just replacing parts that are hard to change, expensive and not easy to change. It's around 150.00, well worth it. Truth is, your pump and filter may be fine.

KEY08

^ what he said. The code should be stored. Or go to an auto part store and ask them to pull the code for free.

DFWdude

+3... You'll never be able to tell without pulling the codes.

My 19 y-o C320 balked at starting yesterday morning in the 39° Texas drizzle. After three attempts it fired up and has started normally since.

It's not a fuel pressure issue, and I seriously doubt it is a fuel pressure issue with yours. My bet is something in the electronics. To start one of these complex electric starting vehicles, I assume there are a dozen or more computer and electrical checkpoints that have to line up in precise order, all within a quarter second. An OBD2 reader will tell you where to start looking. I have a Cenntech reader that costs barely $30 that catches 95% of the codes, because 95% of codes are generic and not specific to MB.

Sometimes I think these cars have a mind of their own. A hiccup one day that doesn't reappear for months/years.

Mud

Everything is just a guess at this point.
Not only look to see what any stored/pending codes are but live data should be reviewed. Typically a stored code will also show freeze frame data of sensor parameters at the time the ecu commanded the fault code.
If not obvious with standard OBD2 then a scanner that can look at individual modules needs to be used.

RubiJeeper

Thanks for the reply guys. It amazes me how many people responded within such a short time. I belong to some forums where i am lucky to get 1 response in a week.

I have an OBD2 scanner coming in the mail today. I will check it out and report back with my findings. Stay tuned!

RubiJeeper

Alright folks, I used the scanner and no active codes, but two stored codes.

0645 Misfiring of cylinder 6 (P0306) - Damages TWC
0629 Misfiring (P0300)

I am still assuming it was misfiring due to lack of fuel pressure. However, I tried to start the car yesterday again after sitting a few days, and it started like normal again, with no codes. Could it have been just a fluke?

KEY08

Could be a fluke, but could be a bad coil or other things causing a misfire

RubiJeeper

1 bad coil would cause an engine to misfire, but it would not prevent the engine from starting. I would turn the car over for about 7-8 seconds at a time for about 6 times or so to try to get it to start. Towards the 6th or so time, I could hear it trying to fire up. Eventually it sputtered to life. This is why I am still thinking it is a fuel issue.

pierrejoliat

I would clear the stored codes and see what happens, may have been a shorting connector to the coil pack or a temporarily clogged fuel injector, I believe if the full pressure was low you would get a fuel pressure code.

Maybe throw in a couple of bottles of fuel injection cleaner and take it for a fifty mile ride down the highway and see if any codes come back, the fact that it ran fine in between acting up tells me it's intermittent at least. Maybe even a loose or crusty connector at the coil pack or fuel injector.

I am a distillation engineer not a mechanic, but I've worked on cars as an amateur for 50 years, this likely just makes me dangerous!

bmwpowere36m3

Intermittent issues are the most difficult to diagnose... that said it could be many things even given those codes. Its going to take more diagnosing and likely waiting for the event to reoccur. Otherwise its throwing darts at the board. I mean, is it the fuel pump, is it the power supply, is it its control (from ECU), is it a clog, is it an injector, fuel pressure regulator, etc...

Personally, I would just drive it till it happens again. If it happens again, then I would keep a scanner handy to check for codes during the event. Like pierrejoliat mentioned fuel system/injector cleaner cant hurt. Maybe consider where you purchased fuel from last?

*edit* and I'm not even suggesting its the fuel pump or whatever. If you truly suspect the fuel pump. I would start by verifying fuel pressure at rail, engine off, during cranking and when running. As far as fuel flow rate, you'd need to disconnect the fuel line from rail and be able to actuate the pump. Then measure fuel delivered over a period of time. Again that only helps if its a very apparent issue, but without a good control or MB specs your results are sort of meaningless.

RubiJeeper

I cleared the misfire code, and it never came back. After that one time of it not starting, it has been starting and running great. No pending codes either. Maybe it was just a fluke..who knows. Cars can do some weird things sometimes. I just replaced the waterpump and timing belt on my 2003 Acura MDX and when I put it back together it automatically threw 4 O2 codes and 2 EVAP codes. I made sure everything was connected, and checked all the grounds. I replaced the grounding strap from the frame to the engine block because it looked corroded, and all the issues went away!

KEY08

Thanks for the update. All modern cars will throw codes for no reason and/or act up with no justification at all. It's just the way of the auto world. Make sure you also have a strong battery at all times.

nc211

Before you go chasing down the expensive German rabbit hole - go buy a $10 bottle of fuel treatment, pour into gas tank, then fill with premium fuel to mix it in.

It sounds just like what any car would do that had a little water in the tank via the normal condensation process that happens with the change of seasons. Since water falls to the bottom of the tank and the two liquids do not mix together - it is usually when the car has sat for awhile that most of the water will get pulled into the fuel pump first. Hence - starting the car.

Ive had that code before too in my computer log - random misfire cylinder 6, and it happened shortly after I bought the car as a CPO with 22k miles and 3 years of age. I poured a can of fuel treatment into the tank - never happened again.

DFWdude

Great suggestion.

I might do this myself even without any evidence of misfiring. Lots of threads here about maintaining batteries with lack of regular driving during the pandemic. But we should also be mindful of water fallout (separation) in gas tanks, too.

pierrejoliat

I agree, I use a bottle of Techron injector cleaner twice a year, I also use Stabil fuel stabilizer on occasion, just because, when I don't plan on driving for a few weeks or so by just driving the wife's car, especially in the winter.
Also, just for fun, Gasoline is Hydrophobic, Ethanol is Hydroscopic, so absorbs all the water reducing the alcohol from 200 proof anhydrous. water is infinitely miscible in alcohol. So ethanol is good for reducing water and scouring out the fuel system.