2007 Audi A6 (C6 F4) SE 2.0 TDI (BRE) Not Starting

[mephistophles]

Here's a summary of my issue

Ran low on fuel a week or so ago but forgot to refuel on way home. Next morning showing range of 15 miles. Started OK but cut out at idle twice on a 4 mile journey to fuel station. Range showing 10 mile at fuel station. Half filled tank and started OK again but cut out at idle three further times between fuel station and destination 3 miles away. This was at 9am. Came out to it at 1PM and would turn over but not start. Briefly started twice but only ran for about a second each time. Battery ended up flat. Battery partially charged but generic OBD2 reader which has previously worked on it would not connect. Display showed ESR Fault/ Auto parking brake fault. After fully charging battery it still wouldn't start but only showed Auto parking brake fault now.

Called out mobile mechanic who diagnosed a faulty in tank fuel pump. Came out today to fit it and after spending two hours, what seemed like "p***ing about" and looking for the fuel pump, which was not under the back seat as expected but actually in the luggage compartment (which I found myself after I decided it HAD to be somewhere!) and the fuel pump relay (which doesn't appear to be in the luggage compartment as it shows in various places online?) came to the conclusion that there is no power to the fuel pump connector, however, there WAS power to the fuel pump fuse.

He has just come back to me with a message saying that "my old boss says that on a A6 C6 there is also a very common issue which is a ignition start relay, which is very likely that given your staling and then cut out, also no power to pump and suggestions that the evu has gave up, My old boss has just looked into it for me, Under drivers side dash small black relay"

Does that sound plausible?

[swalker]

hes not wrong about the relay being an issue - but mine went and the car didn't even fire or crank? ( plenty of posts you should find it on here and what it does does not do) and it was pretty intermittent - along with it the dash lit up like a Christmas tree as the relay fires up the can bus.
it does sound like a pump related issue - he may have measured 12V at the fuse but was there power, ie enough juice to light a bulb or satisfy a tester, but a bad connection that fails under load.

[Crasher]

So no one has done a code read?

[mephistophles]

- he may have measured 12V at the fuse but was there power, ie enough juice to light a bulb or satisfy a tester, but a bad connection that fails under load.

I don't know to be honest - he just kind of put it across the plug and said "nothing there"

[mephistophles]

So no one has done a code read?

Not yet no - I know that the generic ODB reader I mentioned in my initial post DOES still work as I connected it to another vehicle but it gives a link error when i try to connect it to mine. That being the case, would VCDS / VAG-COM actually be able to read anything...or does it work in a different way?

[Crasher]

If it is a non OBDII error such as the crank speed sender, it may not show up so yes VCDS and also check the cranking RPM in measuring blocks.