Fuel coming out of vapor hose for charcoal canister with canister delete

[Ocell]

I've been searching/reading for a day and I can't find anyone with this issue... I'm hoping someone here can shed some light on my problem.

TL; DR:
About 20 minutes into a track session I had fuel start pouring out of the line that would normally go to the charcoal canister. I did have nearly a full tank of gas, but this doesn't seem normal/safe. Even if I still had a charcoal canister the system wouldn't be working as designed, and the canister would get flooded with fuel, right? What would cause this?



Full question:
My 91 318is came with charcoal canister removed. I didn't do the delete, and didn't actually know what the line and valve were for (this is my first E30) so I've been learning about how the charcoal system worked and how to properly remove it by searching over the last day.


The purge valve has been capped off on the canister side, and is still plugged in and connected to the throttle body. (I don't think it's relevant to my issue, but including that note just in case.) Here's a photo of the cap.




The line that would normally feed the charcoal canister has been left venting to atmosphere. I have it zip-tied to keep it at the same height as the brake fluid reservoir. I know a small filter on the end would be best, but I don't think it would fix my problem either.




So I'm pretty sure this line is supposed to only carry vapor from an expansion tank (?) or somewhere on the top of the gas tank.


Yesterday I did a track session with a nearly full tank of gas. I've done that before without issues. About 20 minutes in I could smell gas, so I pulled off track and popped the hood. The top of the frame rail on the driver's side was a solid puddle of gas, right under where my vapor line is venting. I'm assuming it's what was dumping fuel.


What could cause liquid fuel to go all the way from the rear of the car to the height of the brake booster in the engine bay? The frame rail and subframe in this area of the engine bay has missing paint and surface rust, so I don't think this is the first time it's happened. (It's the first time I've noticed it, though, and I've done many track sessions in this car already.)



Any ideas? I think it would best if it didn't do this.

[Ocell]

I just removed the rear passenger wheel and got access to the expansion tank. I got to the top of the gas tank through the fuel pump access door, then verified that I had the lines hooked up correctly, using this diagram as a guide.



I thought there might be a chance that I had gotten the lines for 11 and 7 switched. That would have put the bottom of the expansion tank connected to the charcoal canister line, gasoline would fill from the top and drain out the bottom to the canister line, and what's happening to me would have made sense.

Unfortunately (but fortunately?) all my lines are connected correctly.

I'm guessing this means that my expansion tank is filling with fuel all the way to the top and continues to rise, sending fuel out the top and down the line for the charcoal canister.

What would cause that?

When I fill the tank I let it automatically shut off when the gas pump clicks off, and I don't top it off any more after that.

[bflan2001]

To me, this sounds like the fuel tank is getting vapor-locked. To be fair, I'm not even sure if this happens in cars, but it is a common problem in motorcycles. This is usually caused by liquid fuel getting into the vent lines. This blocks the fuel tank from venting and can cause the air inside to pressurize, pushing fuel up through the expansion tank. The solution in motorcycles is to disconnect all the vent lines and blow compressed air through them at both ends. Try this and let us know if it works.

[Ocell]

That makes sense. But if that's the case I still wonder how fuel got in the vent line to start with.

I'm assuming I could take the fill cap off and push air into the end of the vent line without disconnecting everything?

[bflan2001]

That's definitely worth a shot, it just depends how much fuel is in the line. If it's full, it might take a good amount of air pressure to blow it out. It can happen from overfilling your tank, or I suppose it could happen with a full tank and a lot of aggressive driving. In motorcycles it happens because bikes lean a lot and even get laid down on their side.

[Ocell]

Has anyone with a track focused build with stock fuel system run into this issue? So far the only solutions I've thought up are:

1. Never completely fill the tank (tricky)
2. Drive slower on track (no thanks)
3. Figure out a new vent system (I'm still researching/thinking on how to make something better than stock. I'm open for help there.)

[grinchxvx]

Has anyone with a track focused build with stock fuel system run into this issue? So far the only solutions I've thought up are:

1. Never completely fill the tank (tricky)
2. Drive slower on track (no thanks)
3. Figure out a new vent system (I'm still researching/thinking on how to make something better than stock. I'm open for help there.)

Any solutions to this? My car is Doing the same thing since I swapped if and removed the charcoal canister. I also have surface rust on the frame rail too so it might have been happening for a while and I didn't notice until the swap bit either way I can't figure it out. I've just been not filling the tank all the way and I have a hole drilled in my gas cap and that keeps it from speewing fuel most of the time

[grinchxvx]

I'm going to remove the vent line completely and just put a little filter right off the tank like mentioned above but idk how well that will work

[Dj Buttchug]

The purge valve is designed to release excess vapor pressure in the tank through the charcoal canister and into the intake manifold to be burned up.

Vapors and fuel (because full tank especially on the track with excessive cornering ect) will flow through that line.

OP I would try and put it back to stock and you shouldn't have a problem anymore.

[TobyB]

I was thinking along the same lines-
I race with a stock canister system for just that reason.
Venting a fuel cell/tank on a purpose- built race car
usually involves a 'roll- over' valve, getting some elevation
on the vent, AND some trial and error.

Under braking, fuel goes everywhere, especially forward.
(a 1- g stop is very similar to going down a 45 degree hill-
and how often do you do THAT?)

t