W203 C320cdi om642 more woes! fuel quantity control short ?

[JonathanC250]

Afternoon everyone,

Some of you may remember I was having problems with my car before, that I thought was down to the gearbox. Turns out it wasn’t that, it was the EGR system, which I was suprised by, as I had recently had the car mapped and the egr supposedly deleted.

To try and cut a very long story short, I took the car back to the garage who mapped it, and they said the egr needed to be physically blanked, so I took the car away again and fitted a blanking kit, this made the engine light come on and store a code of insufficient egr flow or words to that effect. So I took it back to them again, they said they would re-do the remap, which they did, I went to pick the car up later, and the car would start, run for about 30 seconds then cut out. Turns out they had killed the ecu, as this time they had removed the ecu and opened it up to do the remap.

Anyway, they have supplied a second hand ecu, carried out the map, and I went to pick it up, and everything seemed ok, no lights on, engine didn’t cut out. It was only when driving to work the next day I noticed a slight power cut when you put your foot down, very similar to if the traction control kicks in and it limits the power. Which I thought maybe it could be that, although the traction light wasn’t blinking. Fast forward to about a week later, driving to work and the car suddenly dies, so I have to coast to the side of the road. Switched the ignition off, restarted the car and it was all ok again, no lights on.
Same thing happened on the way home that night, and the next day on the way to work, and then twice on the way home that night. Still no engine light though. So I plugged my computer into the car to see if there were any codes, there was, 2199 fuel quantity control short to ground, and p0003. I checked the plug and wires as best as I could, correct voltage at the harness, but try and test resistance at the plug, the car cuts out.
So what I ended up doing was leaving the fuel quantity control valve connection off, so that way I could drive the car without it cutting out, albeit in limp mode.
I ordered a new fqcv and fitted that and there is no change. Before I removed the old one and fitted the new one, I plugged it back in and tried to start the car, it wouldn’t start, now the short was a permanent fault where as before it was intermittent. Once I fitted the new valve, exactly the same.

Is there a known failure of the harness on these cars? As I can’t see any damaged casing or wires anywhere in the engine bay, and I don’t want to start cutting all the protection off incase that opens another can of worms!

what are the chances this second ecu is damaged? this has turned into a complete nightmare. The garage are not returning my calls or emails now, they told me there is no warranty on the work they’ve done, when I last picked the car up from there!

Sorry for the long post, this is driving me mad now!
If any of you know of anything else I can do or check, please let me know.
Thanks,
Jon

 

[mersum1es]

Fuel delivery faults are not rare after remapping, if the fuel is worn and system cannot produce enough stuff system may caught for example fqv fault. In SDS there would be separate tests for valve and high pressure test for pump. Unversal codes are not always correct, so I would get ' 2nd opinion'...

Fuel quantity valve faults ARE common but if you bought original MB part, I think rules out new valve would faulty as well.

BTW EGR is not needed to blank if valve is properly shut. You only may do new fault if system is blocked wrong way; back pressure sensor is needed to have access to manifold.

 

[JonathanC250]

T

Fuel delivery faults are not rare after remapping, if the fuel is worn and system cannot produce enough stuff system may caught for example fqv fault. In SDS there would be separate tests for valve and high pressure test for pump. Unversal codes are not always correct, so I would get ' 2nd opinion'...

Fuel quantity valve faults ARE common but if you bought original MB part, I think rules out new valve would faulty as well.

BTW EGR is not needed to blank if valve is properly shut. You only may do new fault if system is blocked wrong way; back pressure sensor is needed to have access to manifold.

thanks for the reply, if the system was worn I would have expected a low pressure code or something similar, not what now is a permanent short to ground

Would the star test still work, as the car will only run with the fqcv harness unplugged? I’ve noticed, when the it’s unplugged, and I turn the ignition on, I can hear the tank pump prime, however with the fqcv plugged in, if I turn the ignition on, the tank fuel pump doesn’t prime.

I’m really regretting taking it to this place to be mapped. All it’s been is a pain in the behind ever since! Wasn’t some riffraff tuner either, was a supposedly reputable company!

 

[JonathanC250]

Also, sorry I forgot to add, the new valve wasn’t from Mercedes, it was a new genuine Bosch valve, matching part numbers.

 

[mersum1es]

Of course valve test won't work if unplugged... really weird problem, if related to primer pump... thats the reason why car does not start if no primer pressure...

If company is really reputable, they should resume your original program without a charge. There should be always such warranty in remap.

 

[jvieira73]

Also, sorry I forgot to add, the new valve wasn’t from Mercedes, it was a new genuine Bosch valve, matching part numbers.

Hi Jonathan, what was the result? I'm havng exactly the same problem with exactly the same symptoms.

 

[W1ghty]

Hi Jonathan, what was the result? I'm havng exactly the same problem with exactly the same symptoms.

He’s not been on the forum since 2021 buddy .

 

[JonathanC250]

Hi Jonathan, what was the result? I'm havng exactly the same problem with exactly the same symptoms.

Hi there,
Turns out the garaged had ruined the second ecu too. Another one was sourced and they sent it to celtic tuning directly to get them to do it. All good after that. Well, that part of it was! Loads of gearbox problems and boost leaks to deal with

 

[JonathanC250]

Fuel delivery faults are not rare after remapping, if the fuel is worn and system cannot produce enough stuff system may caught for example fqv fault. In SDS there would be separate tests for valve and high pressure test for pump. Unversal codes are not always correct, so I would get ' 2nd opinion'...

Fuel quantity valve faults ARE common but if you bought original MB part, I think rules out new valve would faulty as well.

BTW EGR is not needed to blank if valve is properly shut. You only may do new fault if system is blocked wrong way; back pressure sensor is needed to have access to manifold.

With regards to the EGR blank, the EGR valve is still fitted and connected to the harness, and stays steady at 5% opening regardless of revs, I am still getting readings from the back pressure sensor as I'm guessing the 5% opening is using intake pressure instead. As the little EGR elbow that connects between the exhaust manifold Y pipe and the intake manifold has been removed and blanks fitted. I am now wondering if this was another dodgy get around from them and could possibly be the reason I've gone through 3 turbo actuators since? (Turbo vane arm moves freely without sticking )

 

[JonathanC250]

Fuel delivery faults are not rare after remapping, if the fuel is worn and system cannot produce enough stuff system may caught for example fqv fault. In SDS there would be separate tests for valve and high pressure test for pump. Unversal codes are not always correct, so I would get ' 2nd opinion'...

Fuel quantity valve faults ARE common but if you bought original MB part, I think rules out new valve would faulty as well.

BTW EGR is not needed to blank if valve is properly shut. You only may do new fault if system is blocked wrong way; back pressure sensor is needed to have access to manifold.

With regards to the EGR blank, the EGR valve is still fitted and connected to the harness, and stays steady at 5% opening regardless of revs, I am still getting readings from the back pressure sensor as I'm guessing the 5% opening is using intake pressure instead. As the little EGR elbow that connects between the exhaust manifold Y pipe and the intake manifold has been removed and blanks fitted. I am now wondering if this was another dodgy get around from them and could possibly be the reason I've gone through 3 turbo actuators since? (Turbo vane arm moves freely without sticking )

 

[mersum1es]

Are you seeing exhaust back pressure sensor reading changing in live data?

 

[JonathanC250]

Are you seeing exhaust back pressure sensor reading changing in live data?

Are you seeing exhaust back pressure sensor reading changing in live data?

Yes, while viewing live data the value for the exhaust back pressure sensor changes, with revs it increases. But it must be reading the pressure from the inlet manifold as the EGR pipe was removed and blanked so it cant be exhaust pressure. Would that work?

 

[mersum1es]

Definitely it will not work, pressures are all messed and implausible between each others (if it really is reading boost pressure... I am not quite sure hows your tweak made now)

Edit: see if back pressure reading is same than boost pressure reading when revving?

 

[Supernoodle]

Surely the exhaust pressure sensor is in the exhaust manifold or least upstream of the EGR tract, so will still read ok?

 

[JonathanC250]

Surely the exhaust pressure sensor is in the exhaust manifold or least upstream of the EGR tract, so will still read ok?

on the OM642 the exhaust back pressure sensor is at the top of the engine at the back on the nearside, next to the egr valve, in the same housing. But as the pipe that connects the exhaust manifold to the egr housing was removed and blanked, it will not see exhaust pressure as it is physically not connected anymore.
That's why I was wondering if that is why they've mapped the egr to stay at 5% opening constantly so the back pressure sensor still gets a reading.
But I'd imagine the exhaust pressure would be higher than intake pressure surely, then I wondered if that could be the reason the car has gone through 3 turbo actuators since

 

[JonathanC250]

Definitely it will not work, pressures are all messed and implausible between each others (if it really is reading boost pressure... I am not quite sure hows your tweak made now)

Edit: see if back pressure reading is same than boost pressure reading when revving?

If I remember correctly the readings were the same, but I will double check it again when I get a chance over the weekend , thank you for helping

 

[alexanderfoti]

on the OM642 the exhaust back pressure sensor is at the top of the engine at the back on the nearside, next to the egr valve, in the same housing. But as the pipe that connects the exhaust manifold to the egr housing was removed and blanked, it will not see exhaust pressure as it is physically not connected anymore.
That's why I was wondering if that is why they've mapped the egr to stay at 5% opening constantly so the back pressure sensor still gets a reading.
But I'd imagine the exhaust pressure would be higher than intake pressure surely, then I wondered if that could be the reason the car has gone through 3 turbo actuators since

Its before the egr valve though, so it still reads the pressure when the valve is closed.

If it where as you said, the ecu wouldn't see any backpressure unless the egr was being actuate.

 

[JonathanC250]

Its before the egr valve though, so it still reads the pressure when the valve is closed.

If it where as you said, the ecu wouldn't see any backpressure unless the egr was being actuate.

Yes, that is why I think they have mapped it to stay at 5% open at all times, so the sensor still gets a reading as the connection between the exhaust and egr is blanked.

Also, I've recently discovered your youtube channel and have subscribed. Is there anymore happening with the gold C320 cdi you had on there

 

[alexanderfoti]

Yes, that is why I think they have mapped it to stay at 5% open at all times, so the sensor still gets a reading as the connection between the exhaust and egr is blanked.

Also, I've recently discovered your youtube channel and have subscribed. Is there anymore happening with the gold C320 cdi you had on there

They would just map it shut, very unusual to do anything other than completely disable it.

Thanks! Yes the new turbo is going on soon. We had a "lack of employee" issue that is now sorted. The weather is warming up now too so it's a good time to do a comparison. (I have also driven it approx 5k since that last video)

Its on a stage 1 standard tune that we offer, and I'll do another dyno on it in a few weeks, stay tuned

 

[JonathanC250]

They would just map it shut, very unusual to do anything other than completely disable it.

Thanks! Yes the new turbo is going on soon. We had a "lack of employee" issue that is now sorted. The weather is warming up now too so it's a good time to do a comparison. (I have also driven it approx 5k since that last video)

Its on a stage 1 standard tune that we offer, and I'll do another dyno on it in a few weeks, stay tuned

I would have thought that too, First map they done on the original ECU, they supposedly disabled the EGR. had it for a couple of weeks and checked with live data and it was still operating. So took it back to them and that's when they said I need to Install the blanks. So I installed the blanking kit, Instant engine light and limp mode due to no egr flow. So took it back to them again and they had another go and this time said they had to open the ecu to do it, whereas before they were just flashing it. That killed the original ecu, so they sourced another one and done it again, which then leads to the beginning of this thread! absolute nightmare

Nice, I'll keep an eye out for the new vid!