1.9 TDI PD: Cold Start Problems & Solutions

I greet you all very warmly!

I'm having the following problem with my Audi A4 1.9 TDI PD (year 2000, 120,000 km):
'When I try to start the engine, it starts up and then immediately shuts off after just ONE second. After that, it only starts again if you let it crank for about 20-30 seconds AND fully depress the accelerator pedal. This is driving my mechanic and me crazy, because you can only perform this procedure a maximum of twice a day. Because once it starts, it runs normally and starts up immediately without any problems on subsequent attempts. The error memory shows nothing.'
The following parts have been checked so far:

- Glow plugs including control unit.
- Serpentine belt including tensioner pulley.
- Fuel filter

Sometimes I manage to keep the engine running by pressing the accelerator pedal immediately the first time. The engine then runs very roughly and slowly reaches its operating speed. But if it stalls, then it's back to 'struggling to start' again!

Greetings, drifter.

Please search for 'Relais 109'.

Air in the fuel system?

joergs wrote:

air in the fuel system?

... would also be one of my assumptions.

I replaced the rubber hoses between the filter and the engine with clear hoses.
It might get tough eventually, but I want to see how long it lasts.

If there were air in my system, I would be able to see it clearly -> try it out yourself .


Alternative approach:
Does the pre-pump operate within the tank?

Alternative approach:
Does the pre-feed pump operate inside the tank?

That would have been my next tip!

Alternative approach:
Does the pre-feed pump operate inside the tank?

As a tip for this:

The less fuel in the tank, the (even) harder it is to start the engine.

Okay, just out of curiosity, do the PD elements like that rumbling sound, or can they also take damage from it, like some distributor pumps ?

Also,das schlechte Startverhalten ist weniger abhängig von dem Füllstand im Tank, sondern eher von der Motortemperatur bzw. von der Zeit zwischen den Startversuchen. Wenn länger als 4 Stunden gewartet wird treten die Probleme auf. AbHe only does it then!
What about the air in the fuel line? How time-dependent can that be? In my opinion, this theory seems the most likely. It could be that the initial start of the engine burns up the small amount of fuel in the ESP, which then draws in air, the engine shuts off, and only restarts after the air bubbles have been purged, or am I wrong?

drifter

drifter wrote:

What about the air in the fuel line? How time-dependent can that be?

It's highly variable, depending on the size of the air vent hole, etc.

Quote:

It's possible that the initial start of the engine burns off a small amount of fuel remaining in the ESP, which then draws in air, causing the engine to stall and restart until the air bubbles are purged, or am I wrong about that?

It's basically fine - except for the ESP on the PD model .

mahk wrote:

Just as an aside, do the PD elements like that rumbling sound, or can they also take damage from it, like some distributor pumps

As long as there is motor oil available, this shouldn't pose a major problem.

Immobilizer active (engine turns off approximately 1 second after starting):
-> Try other authorized keys, and if necessary, have it repaired/properly programmed.

Brushie wrote:

Immobilizer active (engine turns off approximately 1 second after starting): -> try other authorized keys, if necessary, have it repaired / properly programmed.

I'm less inclined to believe that: it should be possible to trigger it more often than just every 4 hours .