Vent the gas cap on track car?

[Deadeye]

I have noticed that since I put in the 3.6 in my '87 911 there is a vacuum created in the tank. I notice this when I remove the cap to add fuel. Is there a reason I should not drill a small vent hole in the cap?

[juanbenae]

ah, yeah, it'll leak.... do you have the stock tank or a cell?

[Deadeye]

Stock tank, never more than 3/4 full. I'm thinking a 1/16" hole in the cap.

[wildcat077]

Dennis,

I had the same issue after i removed the overflow reservoir and the headlight washer reservoir in the left front wheelwell after my 3.6 install.I had capped the line coming from the tank and the first time i went to fuel the car i was surprised as well to have vacuum in the fuel tank.

Anyhow i removed the bolt i used to cap the line and all is well again,only issue was that i had a small leak from that line after i parked my car on a slope with a full tank ...
I'm going to find a better routing for the line and maybe extend it and run it somewhere under the front bumper !

Cheers
Phil

[wayner]

I did that and almost spun out on my own fuel during a hard right hander!

Went back to stock setup for fuel vent.

[Deadeye]

I still have the stock overflow tank and plumbing in place. Where is the vent to atmosphere?

[wildcat077]

Dennis,

I believe it's routed to the rear of the car and into the charcoal cannister in the right rear wheelwell.I had to remove the charcoal cannister when i installed my ER high clearance oil lines,they just wouldn't fit with the cannister in place.I also removed all the lines and hoses in the engine bay and installed a catch can for the crankcase breather and a separate small breather for the oil tank ...

Did you plug any lines in the engine bay ?

Cheers
Phil

[Deadeye]

No new plugs. The PO removed the canister and plumbing to it. I will try to find where that canister line is cut/ plugged.

[aston@ultrasw.c]

I have the gas tank vent with carbon canister.

However, I needed a place to connect the canister on the 3.6, see thread below.

It works just fine, I don't see why you couldn't connect directly to the port and delete the canister.

Do you still have the fuel separator, white plastic box next to the filler neck hose?

Mine broke so I made a work around. Can post pics later if interested.


3.6 Fuel vapor breather

[Deadeye]

I still have the white plastic fuel separator and the hoses connecting to it. One goes to the tank, one connects to the fuel filler pipe, and one disappears under the wiring bundle. That must be the hose that formerly went to the canister? Does that hose go through the center tunnel to the rear wheel well?

[roblav]

Fuel cells and tanks absolutely require a vent to allow air in when fuel gets consumed. Check sanctioning bodies. Most specify a one way valve in the vent line.

[Deadeye]

Source for one way valve to put in vent hose?

[wildcat077]

Dennis,

I just ordered one today from HRPWorld ... it's a one way Fuel Safe fuel line vent valve,3/8 diameter and they're $14.00 dollars P/N FS-RV38

Cheers
Phil

[Todd Simpson]

I drilled a very small hole in the underside of the cap to address this issue. My car is a '71 and had a 3.2 swap at the time.

I know I get lots of fuel sloshing up into the filler neck at the track but I've never had a leak.

[Deadeye]

Thanks guys.