Fueling Woes

[Shoomakan]

Good evening everyone,

I'm running into a problem with my S3 (1.8T AMK). A few weeks ago at a track event, car started to run out of fuel. Would hit 0.8 bar or so and then go lean and cut.

Been driving it around super gently when I had to, staying below the problem range. First assumption was pump, so I installed my new DW650 today. Sadly, problems persist. Here's what I've done so far:

Checked 4 bar FPR, working fine.
Checked injectors, seem fine.
Fuel pump wiring is correct, pump is priming and sending fuel. Problem has persisted across 2 pumps so I doubt that's the issue.
Hooked in a fuel pressure gauge and it seems ok. Over 4 bar at WOT, doesn't go below 3.5 at idle.
Car is full of gas.
I'm getting a MAF reading via the liquid gauge, but car hits the lean spot before g/s reading peaks.
I noticed that the Liquid gauge and my analog boost gauge are about 3 psi apart (0 indicated on analog gauge, 3 psi indicated in Liquid). Same relative difference at different boost pressures, as far as I can tell.
No ECU error codes via built in Liquid scanner.


Same problem as before. Hit boost, get to 0.7 or so and it cuts, goes lean. Idle AFR is fine, AFR at part throttle is fine.

Only thing I can think of at the moment is voltage at the fuel pump. Going to get in the car with a volt-meter and see if it's getting to 13.8V as it should. Otherwise, I'm at a loss.

Any tips/tricks to help me diagnose this? Anything I missed?

Thank you for your time.

Cheers.

 

[badger5]

if 3bar fpr then fuel rail pressure should read 3bar +boost pressure

log block 031, 001 002 under wot

 

[Shoomakan]

if 3bar fpr then fuel rail pressure should read 3bar +boost pressure

log block 031, 001 002 under wot

Hey Bill, thanks for replying. Fuel bar is 4 bar, and it is reading 4 bar + boost pressure when on throttle. Off throttle, drops to ~3.7 or so. Will log blocks tomorrow, thanks for the tip. What am I looking for?

 

[badger5]

ok, so 4bar fpr yea? so 4bar + boost pressure expected to be seen in the rail..
so if for example running 1.5bar boost, I would expect to be seeing 5.5bar of fuel pressure

when logging, see what block 001 does during the "leaning" out you describe, and see what actual lambda is up to on 031.. 002 will give you the injector ms to calc duty cycle from also, as well as airflow..

If block 001 goes very additive, its indicative of it trying to adjust to achieve the requested lambda, and its not possible either because physical fuel is not there (pressure dropping) OR because your maf is miles under reading and its base airflow to fuel required calc is miles off as a consequence.

If lambda actual goes much leaner than requested its all outta fuel... injectors maxed or pump pressure sagging... usual suspects

 

[ayfreetee]

I assume all your fuel lines are okay, not crushed anywhere.