Golf 2 TD: Intermittent Engine Knocking (1200-1800 rpm)

Hello everyone,

I converted my Golf TD to run on 100% rapeseed oil.
New 297 series pre-nozzle, 180 bar, FB1.17.
New 25mm glow plugs.
WT
el. Diesel heater.
thick feed line.


I've now driven approximately 2500 km with 100% success. It starts up perfectly, but there's a slight hesitation when it's cold, which doesn't last long. When the engine is warm, it has full power, and overall, I'm very satisfied. Thanks to your help, the fuel injector is working again .

"I've noticed over the past week that the engine noise has been getting progressively louder. Even in the cold, with temperatures around 7 degrees Celsius in the morning, it's very loud when running at speeds up to 2000 RPM, and pedestrians almost shake their heads in disbelief."
When the engine was warm, it initially ran smoothly in all speed and load ranges.
My oil temperature is around 55-65 degrees Celsius when the engine is at operating temperature. (That should be okay, right?)

Here's the situation:

Cold start knocking, especially in the suction range at low to medium load, very strong knocking up to 2000!! I'm actually quite used to it, but I'm not entirely comfortable with it anymore.

"During the warm-up phase and when the engine is warm at idle, the engine runs perfectly smoothly without any misfires. When I increase the idle speed (i.e., at the lowest load), there is also no misfiring in the critical range of 1200 to 2000 RPM."

"During driving, starting around 1200 RPM with moderate acceleration (which is very noticeable in 3rd gear with the window open), a harsh knocking sound can be heard until approximately 1800 RPM. When accelerating fully (under boost), the sound disappears."

The knocking sound isn't present in every cylinder or at every stage of the engine cycle; rather, it's more sporadic, occurring roughly twice per second. It sounds very high-pitched and metallic, similar to the sound of a gasoline engine with excessive pre-ignition.
Please excuse the clumsy wording .

Does anyone have a similar or perhaps the same problem, and ideally also knows the solution ?

Okay, the choke has no influence on the occasional misfiring; the engine is functioning correctly, which you can clearly hear during operation and when starting.

This phenomenon strongly suggests a faulty nozzle, or what do the experts say?


Best regards,

Frank.
Please provide the German text you would like me to translate into English.

We experienced exactly this phenomenon with the old, original Duesen at the JX event.
It was especially nice to listen to while stuck in traffic on the highway.

As far as I know, the new pre-combustion nozzles (also known as type 297) have eliminated this problem.

If only occasional clumps of material are present, it's probably not the nozzle, because if it were clogged, it would likely cause a buildup of material over a longer period.

I think it's more likely that the nozzle will "stick" or "drip" because it's not quite working properly with the spool. Although, that's strange for new nozzles.

I cannot offer you a definitive solution.

m;

Hello,

You're right, I experienced the same phenomenon with the original nozzles, but even more intensely. It was better with the new nozzles at first...

Even when idling, it no longer runs smoothly on all 4 cylinders. You can tell by listening to the exhaust, or by feeling a strong vibration in the steering wheel and dashboard.

Best regards,
Frank.

Hello,

Problem of nailing solved
After I stood there, looking like an idiot, at the running engine for a good 10 minutes, trying to spot any leaks, it happened .

The original plastic return line, which I cut and connected to the first injector with a T-piece to keep the oil pressure low in the drain lines, was leaking slightly!
With no hope of success, the leak was really a joke, only about one drop every 5 minutes, so I installed a new pipe.
After starting, there was no change, but after about 5 minutes, the knocking sound was gone .
It's incredible how even a small amount of air, even in the return line, can have such a significant impact on the performance of this old tractor engine, isn't it?
What I don't quite understand is the fact that air in the return line has such an effect when the engine is running. Oil is constantly being returned through the return line, and the air shouldn't be getting back to the pump, right??

Greetings.

Frank.