PD: Empty Tank - Troubleshooting Guide

Hey fellow mechanics,

It is well known that with VP-TDI engines, it is best not to run the tank completely empty, as the lubrication of the VP relies on a fuel supply.
Now I'm wondering how it works with PD-TDI engines. The lubrication of the common rail injectors is also supposed to be provided by the engine oil. However, there are naturally also parts within the system that can only be lubricated by the fuel.
Can a PD-TDI engine be run so low on fuel that the remaining fuel in the injectors is no longer sufficient for lubrication? Or do the injectors simply remain with a residual amount of fuel/lubricant inside?
In addition, the vehicle also has a fuel pump (which you can hear when you turn on the ignition). If the fuel tank runs dry, you stop, and then fill the reserve canister, do you have to prime it for a long time, or is the fuel automatically transported to the injectors by the fuel pump and bled?

Greetings.

Eike.

eike wrote:

In addition, the vehicle also has a fuel pump (which you can hear when the ignition is turned on). If the fuel tank runs dry, you stop, and then fill the reserve canister, do you have to manually prime for a long time, or is fuel automatically transported to the PDE (pre-injection device) via the fuel pump and bled?

Okay, in that case, I would turn the ignition on and off about 5 times until the pump stops.
At least in my engine, the entire fuel system is flushed during this process.

If it still doesn't start right away, try turning the ignition on and letting it pump for about 5 more times.
Eventually, it should start up with its usual eagerness.

Alternatively, I could connect a permanent power source from Dauer+ to the pump fuse, which would eliminate the need for ignition on/off power.

From this perspective, the pre-charging pump is really practical .

Hello,

Is the pump simply controlled by a timer relay? Meaning, does it activate for 2-3 seconds each time? Or is there possibly a sensor somewhere that detects sufficient fuel supply to the engine?

Greetings.

Eike.

eike wrote:

Is the pump simply controlled by a time relay?

So, it turns on for 2-3 seconds each time? }
It's exactly the same with the 9N. Presumably, it's the same with other PD models as well; a fuel sensor in the engine compartment would be completely new to me.

The fuel pump only activates when the tank is less than about half full.

Roger wrote:

With the Golf, the fuel pump only starts when the tank is less than about half full.

That's cute... by the way, do you happen to know how the engine computer gets the "fuel level" information?

Via Can from AI...?

Quote:

Via Can from AI

IMO, it's the only viable option. Does anyone have any other ideas?