TDI won't start at warm engine

[Javier Neog]

Hi guys

I am having a strange issue over here, but may be easy for any of you. I changed fuel injectors to my Audi Q5 3.0 TDI and high pressure pump. Everything seemed ok, but....

Cold engine:
I press start button, it cranks up for about 1 second and engine fires up. It always fires up on cold engine. I turn off engine and on again without problems.

After driving for some time until engine heats up, I turn it off. Then I press start button and engine wont start! It may start but sometimes I need to crank for about 30 seconds. It only happens when engine is warm. After I wait until engine cools down, it fires up with no problem.

I really have no clue and haven't found any answer over here. I thought I needed to drive constantly and problem would dissappear but it didn't.

** While driving, glow plugs start blinking for no reason.

I appreciate any help. Thank you very much!!

Javier

[Javier Neog]

Here I share an image with actual values while cranking (warm engine). Does anybody see something odd here?

I am thinking this is fuel pressure related, but my question is... why is the engine working everything OK, but when I turn off then it wont turn on again?

This image show values when cranking and no luck.
no prende.jpg

These are values taken before turning engine off.
medio2.jpg

[Rob69]

Should hot cranking speed be above 280rpm to start ?
Maybe others could confirm.....

[Javier Neog]

Hi friend. Even at higher rpm it won't start.

I've found, after a lot of tests, that my maintenance valve (the tiny barrel at the injector return lines) is from a 2013 model, and is different in size than a 2011 model. I did a trick to my engine. I squeezed a little the return line after the maintenance valve with a wrench, and it caused the engine to start, even at a warm temperature. Without the wrench it is not possible for the engine to start. After it starts, and without the wrench, engine stays on and with no problems at all.

I think the pressure at the return lines is not enough because of that valve. I must find the right one.

Wish me luck!
Javier

Here is a picture of a 2011 vs a 2013 model.

2011


2013