My 312d is driving me crazy...

[pgp13382]

Hi guys,

Last year I bought a 312d from 1995 (James Cook version), and after changing oil and filters (minimal maintenance) we drove it with no issues for about 10.000 km (Spain - Norway) for about 20 days. Months later the well known "limp mode" started to show up regularly and more and more frequently. (Yes, I have read all the topics all over the internet, and spent quite a few bucks on it already). So, here's the funny thing, symptoms and actions taken so far to isolate this loss of power and prevent additional ones:

- The van losses power randomly (110km/h limitation, uphill goes down to 40-60km/h).
- No codes registered in the ECU (none detected via Xentry - HHT, neither via other alternatives, I can access the ECU, read real time values etc, but no faulty codes stored)
- Brand new EGR (but blocked so it doesn't work anymore - just left it there looking good for the annual test)
- Brand new injectors (all of them)
- Brand new turbo unit (it started leaking a bit of oil through the intake side so I change it)
- New high pressure diesel pump (+ fine tune adjustment)
- Redid all cables going from ECU to Sensors, and its connectors.
- New radiator (this is non related, but ok)
- New diesel filter system (the voss connectors suck, the seal cracks and air goes into the filter/pump, so I changed it to a different system and no air incoming anymore)

As you can see some of those things have been done not only trying to tackle the issue, but also to avoid further issues in the future and keep the van as good as possible.

The van is still limited, and the only thing left is the ECU itself. (other than worn out pistons, which it doesn't make sense as the issue happens randomly but more and more frequently. (re-starting the van not always helps in that sense)

Am I (and the mechanics involved so far) missing something else?

Thanks!
Paul

[pgp13382]

I forgot to mention these items:

Brand new head gasket (one inyector was totally stuck so it had to be removed "the hard way"...)
No oil consumption.
No coolant consumption.
No smoke at all.

[Schrauberlein]

Hello,

Have you checked the boost pressure?
If something is leaking or is not regulated correctly, there can be a significant loss of power without an error being recorded in the control unit.
Be sure to check the air hoses, intercooler and vacuum system.

Many greetings

Armin

[speedbug]

Hi there,

As you said you changed the turbo I guess you also checked the vacuum lines to the turbo acuator?
And the connection of the actuator to the waste gate itself… your problem sounds just like mine in the very beginning …

Cheers

Andreas


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[pgp13382]

Hi there,

As you said you changed the turbo I guess you also checked the vacuum lines to the turbo acuator?
And the connection of the actuator to the waste gate itself… your problem sounds just like mine in the very beginning …

Cheers

Andreas


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Yes, all brand new. Turbo and pipes.

[Kasimir]

Has the pressure box also been replaced when the turbo was renewed?

What gearbox do you have? A failure in the gearbox may also cause the system to switch to limp power mode.

[pgp13382]

Has the pressure box also been replaced when the turbo was renewed?

What gearbox do you have? A failure in the gearbox may also cause the system to switch to limp power mode.

Hi, the turbo was not renewed, but changed completely by a brand new one. The van has a manual gearbox.

[Kasimir]

Okay. Did you check all hoses that have something to do with air pressure? Also, the vacuum pump? It seems it also operates the air system of the interior as well as the Niveau regulation of the front lamps, so there seem to be a lot of small hoses for that.

Then, there’s a Relais switch „K5“ that is responsible for powering the main computer. Did you change that one already? Relais may oxidize, although it’s a rare case.

That’s all I know that could be the cause of an error. Or you solved it already, but a different one occurred that is now causing the safe mode. It may be useful to read out the error logs again, if this was the first thing you did when the problems started.

[pgp13382]

Okay. Did you check all hoses that have something to do with air pressure? Also, the vacuum pump? It seems it also operates the air system of the interior as well as the Niveau regulation of the front lamps, so there seem to be a lot of small hoses for that.

Then, there’s a Relais switch „K5“ that is responsible for powering the main computer. Did you change that one already? Relais may oxidize, although it’s a rare case.

That’s all I know that could be the cause of an error. Or you solved it already, but a different one occurred that is now causing the safe mode. It may be useful to read out the error logs again, if this was the first thing you did when the problems started.

Yes, all the vacuum system is bran new as well. Pierburg valves and connectors and pipes. The valve that operates the recirculation flap is brand new as well and working well. I have checked the error codes on a daily basis, no errors found, no errors stored from the past. The relay has to be working because I never had any issues connecting to the main computer and reading real time values. That's why all this is driving me crazy (instead of driving me somewhere, which is why I bought the van)

[Kasimir]

Okay, now it’s really getting complicated. Are you using the Mercedes star diagnosis device or some non-proprietary one? I heard you can only rely on the original device.

[Boxerspezi]

does the Cook smoke black while performance is required? Can the engine get rid of its exhaust gas? Decades ago, I had a defective silencer in my Ford Capri... a loose sheet metal was blocking the exit of the exhaust gas

Gruß
Georg aus MOD

[pgp13382]

Okay, now it’s really getting complicated. Are you using the Mercedes star diagnosis device or some non-proprietary one? I heard you can only rely on the original device.

so far we have used: Mercedes original, mercedes China copy, Bosch, and an older Delphi version that supports this model. Same results on all of them.

[pgp13382]

does the Cook smoke black while performance is required? Can the engine get rid of its exhaust gas? Decades ago, I had a defective silencer in my Ford Capri... a loose sheet metal was blocking the exit of the exhaust gas

Gruß
Georg aus MOD

No smoke at all.

[KlassikJames]

Schwarzer Rauch entsteht bei unvollständiger Verbrennung von zuviel Diesel mit zuwenig Sauerstoff.

Kann auch am Luftfilter liegen oder am „Tuning“.

Gruß,
Klassikjames

[HerrmannOnTour]

Das AGR zu blockieren führt je nach Steuergerät zum Notlauf. Mein 312er geht nach kurzer Zeit in den Notlauf wenn ich das AGR blockiere.
Ansonsten war letztens der Drucksensor bzw. eher dessen Verkabelung bei mir hin. Hat auch zum Notlauf geführt.
Des Weiteren habe ich zeitweise Leistungsverlust wenn es ein Leck in der Luftzuführung gibt. Bei mir regelmäßig kaputt: Dichtung zwischen AGR und Mischgehäuse. War aber auch mal die Dichtung zwischen Ansaugbrücke und Kopf, hinten am 5. Zylinder. Zur Diagnose von Leckagen einfach mal Druckluft (max. 200mBar) auf den Ansaugschlauch geben und die Strecke bis zum Zylinderkopf mit Lecksuchspray bedüsen.

Nach deiner Schilderung sollte das Stilllegen des AGR wohl nicht das Problem sein, da der Notlauf nicht immer kommt, richtig?


Viele Grüße,
Matthias