111.944 Starting and Operation Issues

[Liloff]

Hey guys,
Need your help.
The car was running just fine. All of a sudden started switching off the engine as if there is no enough fuel going to the rail.
Then ended up complete impossible to drive. Engine simply was shutting off and not starting (manual gearbox).
Waited for a friend to pull me to his garage where we could check things more thoroughly.
At first i called a bunch of buddies and what i thought as well was either fuel pump or fuel filter. A friend had a lot of issues with the filter, thus i was shooting for it. He literally described the same issues i was facing on my car and said the problem was the filter.
So far so good... still could be the pump though.

Anyhow, after a while, being pi$$ed and waiting for someone to show up, i tried starting the car and it started perfectly, with perfect idle, however not possible to go over 1600-1800 rev. When Kompressor starts, engine cuts off as if there is no enough fuel to support this. Doesnt look like Kompressor failure to me, as i managed to reach over 3K rpm for a while. Magnetic clutch works as it should, etc. Unplugging the MAF doesnt work. I know it's controlling the Kompressor.

But still... car keep perfect idle (whenever i manage to start it). Thus this is not caused by plugs, cables, coils or spark heads (or whatever the rubber things going over the plugs are called).

We changed the fuel filter (I was putting my stakes on this as the most likely cause). Fuel pump seems to have quire high debit and working perfectly fine...

Don't know what it could be.
There is a vacuum regulator on the injector rail that could possibly be the cause. I will test replacing it, however does sth come to your mind related to the case?

 

[Liloff]

Quick update:
I guess i was a bit frustrated yesterday. Today had the chance to properly test what could be the issue.
I have a Carsoft which often is good enough to resolve the error codes. I somehow find it suitable enough for the task. Seen Star/DAS, worked with it, i don't think it will figure out by miracle the issue.

So what i've done today:
I played a lot with the MAF plug, the Throttle body + the Air Circulation flap on the filter housing. This lead me to the following conclusions:
Supercharger can be cut off not by disconnecting the MAF, but by disconnecting the Circulation Flap. Totally kills it. Which was good for testing. Car ran well started for a while, then erroneous behaviour started again. I cannot find the connection between errors. I deleted the ME + throttle adaptations and in theory the ecu shall be left without any "bad" memories. Done this many times before... however the issue was still there, without any error warnings.

It's not the crankcase valve that is bolted to the engine cover. On a BMW of a friend of mine, it had caused a lot of trouble. I was hoping it was causing the issues... proven me wrong. It's not!

Not the fuel pump as well, working steady and fine. After cleaning all the errors again, which were caused by plugging off the MAF, throttle and the flap, started testing all over again. I am a computer person and know how to troubleshoot (hopefully).

Outcome: No errors whatsoever even after the erroneous behaviour of the engine.
---
Done some research again today and the only thing i have left behind is the K40 relay that is famous for causing issues with SLKs (and CLKs I believe). It's inside the box with the diag connector in the engine bay. However reading about it, leaves me with the impression that it shall throw some error code and lid the engine check light. This is not the case with me. No lights, no errors. The engine management reads that everything is OK, however car doesnt work properly.

The only thing that i am thinking of is that it can still be the fuel filter. A friend of mine told me quite convinced that this is a crappy filter, not allowing enough pressure to the rail, causing the shutoffs at higher revs.
Tried to eliminate this yesterday. We put some $hitty small filter to bypass the system, however it's really small in size. Could well be an issue caused by it. I am ordering tomorrow a brand new aftermarket filter just for testing purposes. If it turns out to be the issue, will buy a new one from MB and forget about it for a while. Oddly enough, the fuel pump has a fixed debit and the filter is quite simple, no vacuums or anything. Just inlet+outlet valve. Nothing fancy, nothing scary...

So, what I'll be shooting for tomorrow is:
1. new fuel filter.
2. K40 relay check inside the "black box"
3. take it to the dealer. I know some people there. Dealership tech guys are convinced they can find the issue quickly.

Hopefully i won't end up with 3. just for the sake of challenge. I want to sort it out myself. (BMWs are easier to troubleshoot).

Please let me know guys if you have any thoughts.

Oh... by the way. How does Kompressor (supercharger) lubrication work. Is it a separate system, is it using engine oil, or is there no lubrication in the charger at all. That i have no clue about and is worth checking, however didn't find any relevant info on the net.

 

[momomo]

The komperssor has its own sealed reservoir of oil that it uses. Its not alot but to drain/replace the oil you will have to take the kompressor out i believe.

 

[Liloff]

Quick update after a long time (sorry for the delay).
Turned out to be a dying MAF. We plugged a BMW one. The car started working OK, not fine, but still much better compared to what it was before. Looking at the live data from the MAF, it turned out that the ECU was reading extremely high amount of air going through the MAF and trying to match the fuel mixture by literally pouring litres of fuel through the injectors.
After replacing the MAF with a new Pierburg component, it's all great again.
Hope you won't experience that frustration...ever!