Audi A4 B7 1.9 TDI. Starts only with starting fluid

[PetruU]

Good morning and Happy holidays to everyone!
I have a problem with my Audi which I cannot solve and I need some help please.
The car: Audi A4 B7 1.9 TDI 115bhp, no modifications.
I changed the timing belt kit 10k miles ago with water pump and all filters. Oil + filter about 1000 miles ago.
The only problem I had was EGR valve getting dirty (I live in London) but some additive every 3 months made the car like it was new.
The car used to work perfect until now.
The problem:
Few days ago I tried to start it but it didn't.
The rev goes up to 200rpm but doesn't start. I called a mobile mechanic who tested it (VCDS and another diagnose machine which I don't remember how it was called) but there was no error.
In the end he sprayed some WD40 in the intake and the car started! No funny noises, all working good.
I used the car until yesterday when it didn't start again.
I read on Google that it could be tandem pump/vacuum pump but the brakes work like it should.
Injectors are in good condition and like I said once the car starts, it works perfect.
If someone had the same problem, can you please help me?
Thank you very much!

 

[Adrian R]

Out of interest can you try jump starting it from another vehicle. if the battery is weak and it is like the other pd engined VWs they need a specific rpm to be achieved to start and a weak battery can fall short of the required rpm.