Lupo 3L: No Power, Blue Diesel Smoke

Hello, you diesel enthusiasts!

Currently, I'm having a lot of trouble with my Lupo 3L...

I bought it knowing that it didn't have much power, and I thought I could easily handle it.

The engine starts normally, but produces bluish smoke (smells like diesel, not oil), and runs very smoothly, which could indicate late injection timing. However, it starts on the first try, which contradicts this, as it should be reluctant to start if the injection timing is late.

The engine barely has enough power to move the car from idle, let alone when the turbo is supposed to provide boost.
The turbocharger is smooth-running, the VTG is smooth-running, and the turbocharger has no shaft play.

First: there are no error codes stored! All measured values are within the normal range, especially the mass airflow, idle speed control, synchronization angle, and fuel injection quantity – everything is fine.
Okay, regarding the mechanical aspects: The catalytic converter was inspected with a camera and appears to be completely free. However, it was tested without the exhaust system, and there was no noticeable difference.
Intake passages are completely clear. Throttle valve and EGR were temporarily deactivated, but there was no difference. Air filter and diesel filter are new.

What I would check next is the timing of the timing belt to see if it's correct. However, I might also try adjusting the camshaft a few degrees earlier for testing purposes.
Adjust the PD (pupillary distance) elements according to the specified requirements.

But I'm really running out of ideas.

Do you have any suggestions?

Sure, no problem! Here's the translation:

"Thank you very much in advance!"

Hi, hello,
What are the compression values?
Could a hose in the air intake system be collapsing, causing it to start and then stall?
hg
Herbert.

Is boost pressure being built up under load?

Thank you very much for your answers!

Herbert wrote:

Hi, hello, What are the compression values? Could a hose in the air intake system be collapsing, causing it to start and then stall? Herbert

Even with the intake hose removed, there is no difference.
I still need to test the compression, but there's no excessive pressure in the crankcase. Generally, the 1.2 TDI engines are very reliable, and I've never seen compression loss in this engine before, but it's on the list of things to check.

Rüdi wrote:

Is boost pressure being built up...under load?

It doesn't really get that far because it has so little power that you can't drive it on the road. It's only suitable for maneuvering in the yard. However, the turbocharger spools up noticeably when I adjust the variable turbine geometry (VTG) to the maximum setting while the engine is idling.

Hello,
I don't have the brilliant idea myself, but here are a few basic thoughts that might be helpful.

I would rule out turbochargers and boost control systems based on the described performance, as the engine simply doesn't reach its full potential.

When starting, there must be enough hot air and enough atomized fuel for the engine to start as described. Therefore, the compression, initial injection amount, and injection timing must be correct.
"Just, do you have to warm it up for an unusually long time? Does the car immediately start emitting a blue cloud after being started, or only when you try to accelerate?"

The blue smoke and lack of power indicate that the fuel injection is occurring much too late. I initially experienced this with the Passat mentioned in my profile (WK diesel with a particulate filter), which had starting problems because the fuel injection was significantly delayed.

I would first check the valve timing and PDE settings, and then investigate why the injection timing might be unintentionally pulled too late while the engine is running.

hg
Herbert.

Perhaps it's worth checking if a master tuner was involved (dataset). If the synchronization angle is correct, a faulty injection is unlikely, unless the crankshaft position sensor is malfunctioning. How does that sensor work on this engine?

Hi!

Is there perhaps a valve or shut-off device that has an intermediate position?

Best regards,
pretzelman01

Thank you again for your ideas!

Unfortunately, I didn't have much time to watch it, but I tried again this weekend.

In my opinion, all the measuring devices show optimal values.
Finally, I inspected the external condition of the PD elements and checked the tilt lever play. It was exactly 180 degrees for all three, as if someone had just adjusted it.

The new tandem pump is definitely suspicious.
Perhaps the old tandem pump produced debris that is now clogging the positive displacement elements.
I will be removing the PD elements this week.

I experimentally adjusted the synchronization angle in advance, and I immediately observed a reduction in smoke emissions.
Then I tried setting it to +4 degrees again, and with the engine warm, I no longer observed any smoke, and there was noticeably more power. However, when the engine cools down and is then started, it smokes again, producing a bluish smoke with a smell of unburned fuel.

My suspicion definitely lies with the fuel injectors. They might be clogged, or possibly damaged due to incorrect adjustment attempts. If they are, for example, dripping fuel, this could explain the good starting behavior combined with late injection timing.

The thermostat, like in most Lupos, is also defective and barely reaches above 60 degrees Celsius. It's a good thing the Lupo doesn't have a temperature gauge...

Hi,

The fuel injection volume at idle and the long-term fuel trim appear to be normal.
No performance: What is the maximum fuel injection amount at full throttle?
Check MWB 8 in the ECU; the power curve is defined by the transmission's torque limit.

Is the airflow through the machine okay? As a rough estimate, a ratio of 20:1 between air (in mg/h) and diesel (in mg/h) at the rated power point would be good.

If that's appropriate: Does a Schlaubi have two cylinder head gaskets installed, or one that is excessively thick?

Best regards, Rainer.

After a long period of inactivity, I finally started working on projects again.

As a last resort, I wanted to take a closer look at the pump nozzle elements.
They were surprisingly easy to pull out.
It seemed like the sides were already very worn down where they would rub against the cylinder head.
I replaced the seals, and lo and behold, the engine runs without blue smoke and with all its 60 horsepower .
Apparently, the middle O-rings were leaking so badly that the diesel was flowing directly back into the tank, and the PD elements were unable to draw in enough fuel.
In the process, the workshops have already replaced everything they could, including the tandem pump, diesel filter, air filter, and apparently also the turbocharger.

Now, the little Lupo is running on diesel again.

Thanks again for your great support!

Thank you for the feedback! X

Without a genuine lambda sensor, it's difficult to detect the problem through diagnostics unless the system is disassembled.