starting from cold takes longer to fire up

[s2_bo]

Since about a month or so my 8 has started to need more cracking to fire up on a cold start.

Happens every time it starts of it hasn't been on for 12 hours or more.
Takes about 5 - 6 seconds to fire up and once its been on it only takes 2 - 3.

Any one else had this issue? or know what it could be, I'm not really to bothered at this stage but obviously want to get it sorted if its something that could stop it starting all together.

[Conan_the_Librarian]

Have you got VCDS (VagCom) to do a scan?

[ainarssems]

Could be several things.

I would start by looking for vacuum leaks.

Followed by VCDS read for faults and realtime data measuring blocks, then spark plugs, coils, injectors, leaks in fuel system and camshaft and crankshaft position sensors.

[ainarssems]

Actually make VCDS read first as it is easier then looking for vacuum leaks and could point You in right dirrection straight away.

[s2_bo]

Thanks guys, i dont have vagcom here as im in france and only have my mac.

Ill have a look for vacuum leaks though, i just fixes a massive one in one of the breather hoses with a new pipe but it hasnt changes anything.

[Just_Ben]

I would suggest that this is most loiekly to be the fuel pump. As the pump wears then it can allow fuelt or un back to the tank over a period of time. It needs to retain a level of pressure even if swiched off for several hours but this can drop and the pump not only needs to raise fuel pressure to a satisfactory level to achieve a quick start but also then needs to pump fuel up from the tank to the injector rail, this can take a couplef extra seconds. Worth having a check!

Other possibilities are: Cam position hall sendor - f this fails thenthe engine needs to turn over several times so it can work out camshaft.crankshaft corrolation for ignition timting,
Fuel Pump relay - this can fail and shut off all power to fuel injectors and pump
Low compression! - If the engine has low compression it'll be harder to start when cold, but this is VERY unlikely!!

[ainarssems]

Regarding fuel pump wearing out and allowing fuel back in the tank. You can test it by turning ignition on/off couple of times for several seconds before You start engine, this will allow fuel pressure to build up and engine will start straight away. But that could also mean leaking fuel pressure regulator. Or You could undo fuel hose going to the injector rail next day after car have been standing and see how much if any pressure remain there.

But this is all just guesswork You really should get it diagnosed on PC. If there is intermittent problem with sensors it will show up as fault and You can check for air leaks by looking at measuring blocks from MAF, knock sensors, engine load , O2 sensors and injection times.

[s2_bo]

Thanks guys, ill see what i can find! Will update on here once i have done some poking around..
Thanks for all the input.
Bo