I recently was on a trackday with my 07 Vantage.
During the first set of laps (starting with 1/2 tank of fuel) everything was fine.
After refilling, with full tank, the car developed a stutter, which felt like fuel starvation.
It always happened at the same corner combination, a 4th gear uphill left turn followed by a strong braking into the subsequent 3rd gear right turn (long corner ~180°).
The stutter would start at the end of said corner and return in the next left corner.

After I went out, I opened the fuel filler cap and noticed two things:
- first the filler was wet with gas on the inside
- second there was a vacuum in the tank, as I could hear the air beiing drawn in.

The process repeated during the next turn, afterwards I managed to (almost) avoid it by braking earlier and taking the 180° corer slower.
There was no shown error warning etc on the dashboard.

When I read the workshop manual, it says:

As I read that, the check valve should avoid any fuel sloshing back onto the filler cap.
So my conclusion so far is:
- Check valve does not properly close
- fuel sloshes against filler cap inside and that fuel blocks internal vent
- vacuum build in the tank and prevents proper fuel delivery.

Does anyone experienced something similar?
Does anyone know if the fuel filler cap really has a ventilation inside?
Other thoughts?

 

1st, the fuel cap does vent. You can check the spring movement to verify with a small screwdriver lightly insert in the center of cap an it should move a few mm.
2nd one thing that does occur with a full tank and turning is a vacuum vapor line that can split (inside the tank) that supplies fuel vapor to the purge valve. But if it's split it supplies fuel which is drawn into the intake manifold. Usually causes a stall condition but if you're in a higher RPM it's going to stumble with added fuel. Quickest way to check is to remove the supply line at the purge valve to check for raw fuel. This is of course when the symptoms are present.
JW

 

Thanks JW, thats a good point, it could be too rich as well.
Any hint on which line (in this snake's nest) is prone to splitting?




On second thought I guess nothing is wrong with my check-valve at the end of the filler tube.
The preload on that spring against the ball inside must be rather weak in order to let the fuel in.
That means the ball in the ckeckvalve can be forced to open during a hard left hand turn.
What is certainly not correct is the check-valve inside the filler cap, which seems to stuck closed for some reason.
I'll examine.
Looks like there is need for a "track pack" containing
a filler cap without valve to ensure no vacuum can build
and a plug for the line #10 entering the plenum to avoid flooding with fuel.
Quite a complicated system to prevent a few drops of fuel getting out...

 

Rich did a good DIY check and repair information on his site.

https://www.redpants.lol/diy-fuel-va...rculation-hose

 

Great, thanks!
Will have a look during the week.

 

I checked the hose acc to Rich's manual, but that hose is intact/tight.
The check valve in the fuel filler was rather sticky and after initially opening it manually still required lots of vacuum (sucking) to open.
So I think I stick to my "plan B"
In the worst case this will trigger an error code, which can be deleted after removing the "track pack", no?
Having said that, I should check if there are un-notified errors in storage...however, the DB9 error manual says all the described errors should throw the "MIL" light.

edit: checked and there are no errors stored.