Hey guys 

my 2011 2.0tdi avant broke down months ago with a catastrophic high pressure pump failure.

Ive been working on it myself and have installed a second hand pump purchased from a dismantlers. Dropped the tank to clean it, installed a new tank lift pump, new filter etc, new fuel rail with new valve and sensor, used but tested injectors which I coded and cleaned all the fuel lines out. 
I also installed a new timing belt kit and water pump.

But despite weeks of head scratching it won’t start. I don’t have vcds, I have a launch one with full functionality for Audi. 
I’ve primed it every way possible. Tested the low side pressure and quantity and that’s all fine. 
while cranking sometimes rail pressure barely increases. I noticed if I press the accelerator pedal while cranking the pressure will eventually build and sometimes it’ll start but immediately stall when it does.

sometimes the rail pressure will hold after cranking and sometimes it will drop instantly.

The rail pressure sensor constantly fluctuates  without cranking reading between 900-1200kpa even when I’ve fuel pipes removed at the rail. 
tested voltages at the sensor and its what it should be. 
Tested the wiring back to the ecu for the fuel metering valve and the rail pressure valve. Again all good.

even when the car starts briefly I don’t get any fault codes. 
 

im wondering if the fact that pressing down the accelerator pedal will help build fuel pressure is that down to the ecu alternating the duty cycles on metering or rail pressure valves due to a higher demand? 
can anyone tell me what those duty cycles usually are on and before starting? Also what is a normal fuel pressure reading for a fuel rail that’s doesn’t have any pressure or when the system is fully bleed?

Sorry for the really long post and thanks in advance if anyone has any suggestions 

 

 

Has the replacement fuel pump been coded to your current car ECU and instrument cluster? 

I ask as I know even on my older A6 C5 the fuel pump has to coded to the instrument cluster and ECU as it's an anti theft measure and part of the imobiliser system. 

Hi Steve. As far as I can tell there’s no coding to do on mine. The only thing I can do is reset the learned values for the fuel metering valve and the rail pressure control valve which I’ve done but made no difference