1.9TDi AFN engine starting problem

I have been struggeling with my 1999 a6 1.9tdi 81kw. I have replaced starter and G28 sensor,fuel return valve and glow plugs. VCDS doesnt show any error codes. Timing is in good range. Sometimes it starts normal and sometimes like in the video below.
https://www.youtube.com/watch?v=NyfAgU6zKvQ

When you say timing is in good range you mean on the basic settings timing graph? What about your iq (channel 1 in measuring blocks)? Also good idea to check group 7 (coolant, air & fuel temp) after the car has been sitting for a while or overnight. Compare the temps you are seeing to what the actual temps in your area are supposed to be and make sure that the sensors are all fairly close to each other in temperature.

Have you noticed any other factors that cause it to start up like that? I mean if its very cold outside / hot outside or after its being started when the engine is already warm etc. Some more info would be useful.

Yes i mean timing graph. Some time ago i checked group 7 and everything seemed ok. Air temp difference was maybe 3 degrees.
When the temperature was about -7 outside then car started very good. After the car has started then next start is sometimes good and sometimes bad. Strange thing is that i can start like few times in a row and every start is good and next minute it starts like in a video.
I try to connect with vcds some time and post here some results. And sorry if i explain so difficult, english is not my main language and it is hard to explain what the car is doing Thats why i made the video.

Today i checked with vcds again. Weird thing is that when i checked timing in october then it was between blue and green line. Is my pump bad?

In my opinion, your fuel is hot and your timing is advanced. Cut it to the middle of the graph and try again. Figure out if the fuel is really that hot of if your fuel temp sensor is bad. Hot fuel reading means the ECU should make the timing more retarded.

I assume that is a snapshot of the timing as the car is running. One of the symptoms of a failing pump is it will not track well. Your VCDS program will give a 'cloud' of points that the timing will change constantly.

There are a lot of things that can keep an engine from starting. IQ that is too lean would keep the engine from starting, any leak between the fuel tank and injector, a leaking injector, a pressure relief check valve with the roll pin sticking out, leaking thermostatic Tee, leaking front seal, or for that matter, any of the other seals, like for IQ or head, leaking injector lines. Those are all good start for things to look for.

There are a lot of cars that have hard start issues from the programming not opening the IQ enough to cause proper startup fueling. Even your setting of the IQ, if too far to the right, as viewed from inside the vehicle(hammer mod leaner means moving the IQ toward the timing belt side of the engine to reduce fuel and give a higher IQ number).

That is a start. Most leaks are age related. The older the pump, the more likely seals leak. I think the fuel is hot, but it's not terribly hot. But if you are running a full tank and it's that hot, I'd also check the Thermostatic Tee to be sure it's not sticking shut. Doesn't happen often, but a bad Tee can mess with makeup fueling coming from the tank.

You have plenty to check. Let me know what you find.