2008 A4 Sline Fuel pump no prime when door opens

[sannouni]

hey guys, I've been a lurking in the background here for years... the posts have helped my friends and family (the Audi Owners) solve their Audi related problems. So thank you for all your help (most of the time, a simple search finds the solution, but i wasn't able to solve this one, i tried searching... i dont want to bother anyone unless i ran out of options)

2008 2.0T automatic, S-line, 143000Kms Quattro.

Issue: after parking for over 3 or 4 hours, the engine doesnt start from first crank. replaced battery and no fuel related generic computer codes (no fuel VAG Codes either), there is a right engine mount code, but nothing else.

when the driver door opens, the fuel pump should prime. is that correct??

when the ignition is on, the pump primes, i can hear it. if i wait until the electric (in the tank) fuel pump stops, then normally the engine starts right up.

looking into forums to similar issues, i stumbled upon a thread ( https://www.audizine.com/forum/showthread.php/511714-B7-A4-MT-QUATTRO-2-0T-Do-we-have-fuel-pump-relays )showing how to access the Relay (under the ECU), so i accessed the relays, as described, there are 2 relays (Relay # 614)

None of the relays make an electrical click sound when the door is opened. so i swapped them (same relays just swapped positions), one of the relays was clicking when i opened the door (but no fuel pump priming sound). AND, when the ignition is on, the fuel pump was STILL priming (so is there a bad relay??)

am i missing something/s

i must admit i dont have much experience with the face-lift models (B7), i'm relaying on my experience on the B6, which is not that much anyway. i would appreciate any help to point me in the right direction

Summery:
1) electric fuel pump works
2) timing belt kit, and rear tensioner replaced, along with the cam follower
3) no loss of power, once the engine is on, it works normally
4) purchased a new Relay #614 even though i doubt it'll fix anything, it's on it's way
5) no OBDII/CANBUS or VAGCOM codes (except the passenger side engine mount)
6) engine starts fine if restarted after few minutes (starts right up)
7) Issue only happens on cold starts

[Der Konig]

Do your dome lights come on when you open the door? Just brain storming door switch

[sannouni]

Dome lights come on when the doors open, ... also checked the fuel pump fuse and it turned out to be fine too...

[Jet08]

I believe Der Konig was eluding to damaged wiring in the electrical harness where it enters the drivers door, a visual inspection may shed some light on how likely that is.

[sannouni]

Thanks for the input guys, i looked at the wiring loom and exposed the wires and connector, all was good, no broken insulation on any of the wires. i think it might have something to do with the AMPs going to the relay, or just an aging relay? is there such a thing?

what was strange is when the relays swapped positions, the electrical clicking sound was clear from one of the relays as the driver door opened (but the fuel pump didn't make the usual sound it makes, similar to when the ignition is on)

any help is appreciated. thanks again for the inputs, so far, the driver door wiring loom and the battery are eliminated as potential sources for the problem.

[sannouni]

bump... any posts that i can read to ramp up my knowledge on this specific issue?

the wires in the driver door seem intact, are there fuses or micro-switches to check?
I'll figure out how to check the relays themselves, i read it in the thread that i attached above (just need a 12V source)
fuel pump primes when the ignition is on, even after swapping the relay positions, which could mean that the relays have nothing wrong with them (i have very limited knowledge, so i might very well be missing something)
any other seemingly unrelated things to check for? there are no VAG codes (just a right engine mount), i'm scanning it daily...
the engine does not start from first crank (after sitting for more than a couple of hours), but if waiting til the fuel pump noise stops, it starts right up (most likely fuel pressure is what's making it hard to start, but again, very limited knowledge in this, so please let me know if my conclusion is incorrect)

[Der Konig]

Try looking into symptoms of a failing fuel pump control module next

Sent from my SM-G935V using Audizine mobile app (http://r.tapatalk.com/byo?rid=87676)

[sannouni]

Thanks Der Konig, can you recommend a thread or an article on how to diagnose a faulty Fuel control module?

The car in question is a 2008 Audi A4 B7 automatic Quattro with 143,000Kms (89,000 Miles)

Thanks a million

[Lorenzo816]

Just now experiencing same symptoms.
Ressurect this thread from the dead.
@sannouni did ya solve this?

[Der Konig]

Wow apparently I left this dude in the wind. My b.

Start here

https://www.audizine.com/forum/showthread.php?t=526630

Sent from my SM-G965U using Audizine mobile app (http://r.tapatalk.com/byo?rid=87676)

[esandes]

Check fuse 28 in the driver's side panel.

[Lorenzo816]

Fuse 28 good. When I have a moment to do some diagnosing, I'll post back up. Thx that was obvious after pulling the fuse panel cover. (facepalm)

[esandes]

Are you the OP? Did you follow konig's advice?

[Charles.waite]

Well if the pump works it’s not the fuse.

I recall Hugh@Europa posting a thread about this exact problem. I believe the door switch was faulty. The priming behavior is triggered but the door opening and the ecu or Central electronic module triggering the pump to run for a few seconds on that signal. Somehow that signal isn’t triggering in your case so it’s likely a fault between the ECU and the door. Not the ecu and the pump.

[Theiceman]

only other thing i could think of is a " what if " scenario .
what if.... the car looks at the fuel pressure sensor or some other sensor to determine if it needs to prime the pump when the door is opened. its getting wrong info and does not prime pump, and what if.. this sensor is not looked at with ignition on , it just starts the pump...

just thinking outside the box to create discussion i really dont know anything.

[Charles.waite]

I don’t think it’s that “smart”. I haven’t paid much attention but I believe it primes every time you open the door? Or possibly once every lock->unlock->open door cycle?

It don’t believe it primes “on demand” like what you’re suggesting though.

There is also the key on prime also. So the pump primes twice before the engine starts. Otherwise you get a bit of an extended crank.

[Theiceman]

now i have to actually pay attention when i get in... lol

[Lorenzo816]

Are you the OP? Did you follow konig's advice?

no I'm not the OP. Why does that matter?
When I have time, I'll do some diagnosing. Der konig provided a good link to follow. Thx