Rough cold start despite functioning glow plugs

Hello everyone!

For the past 2-3 weeks, my EGR valve has been starting much more reluctantly and abruptly than it used to. The engine also briefly revs up to approximately 1100-1200 RPM during startup, runs roughly for about 5 seconds, and then sounds relatively normal (for a cold diesel engine ).

Of course, I've already checked the following points:

- Glow plugs with 55W bulb tested, all 4 are okay.
- Temperature sensor readings checked for plausibility (cold and warm), maximum. Sensor deviation of approximately 3°C, which is acceptable according to IMO regulations.

I noticed in a parking garage that the engine emitted a significant amount of black smoke (soot, strong diesel odor) shortly after starting, even though the engine wasn't really cold at the time. This morning, he also smoked a little (+7°C ) and shook.

Reading the data from the MWB13 (idle speed control) reveals fluctuating values. Shortly after a cold start, the values actually appear very good, reaching a maximum. Deviation of approximately 0.3 mg/R.
With the engine warmed up, one cylinder occasionally fluctuates around 0.6 mg/revolution. After a brief, strong burst of acceleration, the deviation returns to 0.3 mg/revolution and then decreases again after 10-20 seconds. The other cylinders have readings that are approximately +/- 0.2-0.3 mg/R.

Actually, it's not that dramatic if my injectors weren't already 30,000 km old, and the ALH engine with 160,000 km old injectors would be at around +-0.1 mg/stroke .

Who knows the answer?

Regards,
Alex.

Hmm, if the fuel injection lines are loose, the engines will also run unevenly because there's residual air in the lines.
-> Are all the cables dry?

Air in the pump can cause similar problems (fluctuations in the pump's internal pressure can disrupt the injection timing control).
-> Try inserting a clear piece of tubing into the return line and see if any bubbles appear in connection with the uneven flow.

[Speculation ON]: A faulty or malfunctioning pressure relief valve could potentially cause similar symptoms. [Speculation OFF]

@ Ulf

What do you mean by "nozzle relief valve"?

Are those the "pressure relief valves" on the high-pressure head of the pump?

m;

dieselmartin wrote:

What do you mean by "Duesenentlastungsventil"? Are those the "equal pressure valves" on the high-pressure head of the pump?

Yes.
AFAIK, not all types are pressure-reducing valves.

Hm ???

What's the difference then? I'm also annoyed that the parts from 1Z cost three times as much as the AFN parts.

@ Alex

Could it be that the nozzles are clogged? Did they work perfectly after installation?
Are we talking about 184s or 205s again? (I'm asking because the 205s might potentially get dirtier if you don't make any other adjustments.)

m;

@dieselmartin:

The nozzles were brand new, and I also replaced the pressure relief valves during this process (they came from my spare pump, which has 39,000 km on it and is stored in the basement ).
The engine ran perfectly after the modification. However, strangely enough, I had very similar problems before the modification, with the old injectors. The car smelled like an old Russian truck. After removing and inspecting the old injectors, it turned out that the injector with the NBF code was faulty. The atomization was poor, and the injector needle tended to stick. A nozzle hole was, in my opinion, completely blocked .

Well, maybe a nozzle will start showing similar failure symptoms again after only 30,000 km.

While atomization might be slightly worse with larger nozzles, the performance is comparable to the production level of the AHF/ASV models, as the AGR, ALH, AHF, and ASV engines all use the exact same pump.
In that regard, there should be no risk from this side, especially in the case of large nozzles.

I suppose I don't have much choice but to at least give the nozzles a visual inspection, do I?

Regards,
Alex.

I'm not a Duesenberg expert.
But:
Besides permanently sealed holes, it's difficult to discern much about two-stage nozzle designs, isn't it?

My tractor smells more like a combustion chamber, but if I rev it up, or especially if it has a turbocharger, a slightly acidic exhaust smell comes through.

He doesn't have any glitches or similar issues.


m;