Alfa Romeo Forums banner

Fuel tank plumbing issues

2615 Views 13 Replies 4 Participants Last post by  Alfacliff
Hey all,
I'm trying to address a fuel odor issue in my 72 Spider (w/Dellortos). The trunk is rank of gas fumes which get into the ****pit while driving and give me a headache, stink up the garage and really keep me from enjoying the car. The smell seems to originate around the fuel filler area. As the photos show, a PO removed the original vapor recovery system leaving it as you see. One thing to do is to address the lack of any vent to the tank (since the vent just is run back to the fill pipe). I was told to replace the little closed loop with a oneway valve to let atmospheric pressure in, but not let fumes escape, so that's on the list (Thanks Alfadan!). Funny thing though, there is no fuel starvation problem, no rush of air when I open the gas cap so somehow air must be getting into the tank. There is no gasket on the gas cap, so there's one place to start. What I'd like to do is remove the tank, get it cleaned, sealed, fix any pinholes and put it back with as simple a system as possible, with new filler hose, a gas cap gasket, the oneway valve and replacing any other sketchy pieces.
SO: what is the outlet from the top of the tank with the hose leading forward on the first photo? Where does it go? Can I just seal this off? And, as you can see in the second photo, the overflow hose from the gas cap area just goes into the trunk(!); the metal pipe it should be attached to is just bent over. Where does that overflow go when hooked up properly?
Thanks for any help! And check out the spider web!



See less See more
1 - 14 of 14 Posts
Bumping this up with added photos
Cliff, Thanks.
So I guess the question is, where does this line come from?
it comes from up front where the spica fuel filter was.
OK. Looking at the numerous other posts of people chasing fuel odors, this line is a typical problem. Since I don't have a FI pump or filter any more, I suppose I can just block it off? It wouldn't still have a function on a carb'd car, would it?

And that still leaves the overfill pipe draining into the trunk...
The Spica system used a recirculating fuel system. That fitting on the top front of the tank was where the fuel return line was.

I recommend that you look out for an OEM vapor recovery tank and reinstall it. That way you'll vent fuel vapor back into the engine intake.

Below is a picture of how the system should be plumbed. What you have now looks pretty dangerous, especially if you're getting strong odors from it.

The drain from the filler cap spill area just goes down through a hole in the trunk floor and onto the pavement.


See less See more
Thanks, and thanks for the nice photo. I'll have to check whether there would be anywhere to send fuel tank vapors on the carb setup. Where did it go on the SPICA system?
So I guess creating a closed system with no place for tank vapors to go is a bad idea (Duh). I suppose pre-SPICA you just had a vented gas cap and called it good. If I can't figure out how to run the vapors for combustion, that is an option. But that's just putting the vapors back in the trunk, so no solution there.
Do you still have the oil vapor separator in the engine compartment?
Not sure, I'll have to check. Only had the car a couple of months. What am I looking for?
i think from my 78 car. the vapor hose goes to the air filter box..but i might be wrong..i lost her 5 years ago.i now run a 84 but it seams likely that that hose would run to the same location...and that is ONE BIG SPIDER..
on the 74 the vapor hose goes to the small tube on top of the intake manafold, the hose connects to the rear, and the front has a hose to the fitting that connects to the vapor seperator.
OK, I'll need to check under the hood to see what's there. The carb conversion was done by a PO, so I don't know what manifold might be have been used. I imagine if it's a Euro intake manifold there would not be a fitting that goes with the SPICA system. What do European versions do with vapors from the gas tank?
Here are photos I took before purchase. Any clues there? Is there a fitting on the intake mainfold for vapors from the tank? Do I have an oil vapor separator?
Sorry to be so dense, but my Brooklands shop manual covers none of this.


See less See more
you dont have a vapor seperator, the hose from the cam cover to the air box goes to the vapor seperator on other models. I dont know how the vent would be hooked up on yours. on my 74, then po change to carbs, the vent, vapro seperator and such was left undesturbed.
1 - 14 of 14 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.