Check valve/fuel vapour separator

[reidyyz]

In the process of improving the reliability, I'm redoing the fuel system up to the carb (tank refurb, new sending unit, new flex lines all around, new elex pump) I found the check valve/fuel separator body disintegrating and was wondering if I can just delete it with a straight flex line. I have removed all emissions from engine bay as it is not an issue in Ontario. This is the white plastic unit bolted to front bulkhead in trunk beside fuel pump. I found a previous 16 yr old thread discussing it, but no definitive answer on if it can be deleted or not. Thx

[18Fiatsandcounting]

I think this has come up before in this forum, but anyway, here's my take on it:

This plastic valve does three things:
1) Let's air into the gas tank if it develops a vacuum.
2) Passes fuel vapors from the tank up to the charcoal canister in the engine compartment.
3) Vents the gas tank if for some reason it becomes severely overpressurized.

You can delete this valve but it may cause other issues. For instance, the gas tank could develop a vacuum as fuel is used, with no way to let air into the tank. Some people drill a very small hole in the gas cap to "fix" this.

Since your valve is disintegrating, you can either find a replacement or a work-around.

-Bryan

[reidyyz]

Thanks Bryan, I appreciate the info. If I get a vented gas cap, do I still need a check valve in inline, or go straight tubing?

[18Fiatsandcounting]

If I get a vented gas cap, do I still need a check valve in inline, or go straight tubing?

I think straight tubing would be fine, but I'm curious to hear from others as to their experiences. With a vented gas cap, the only function you need it to pass fuel vapors from the tank up to the charcoal canister in the engine compartment. If you don't have that canister or plan to get rid of it, I don't know of any reason why you'd need a check valve.

By the way, the charcoal canister doesn't have any effect on performance, but it does reduce the "gassy smell" around these older cars.

-Bryan

[reidyyz]

To clarify, I'm keeping the charcoal trap/canister as I've read several threads saying keeping it doesn't affect performance but will, as you said, reduces the gas smell. I'm also keeping the vapour/liquid separator also to minimize fuel vapour accumulation in trunk and of course the flex/rigid lines between.

Now I just have to find a vented gas cap because as I understand it, the cap will pop open
in both for over pressure as well as under pressure conditions and I'm hesitant to drill a hole and leave the tank to atmosphere all the time.

[18Fiatsandcounting]

TNow I just have to find a vented gas cap because as I understand it, the cap will pop open
in both for over pressure as well as under pressure conditions and I'm hesitant to drill a hole and leave the tank to atmosphere all the time.

I'd be reluctant to drill a hole, too. If you can find a vented gas cap, that would be the ideal solution. Another possibility is a special valve inserted into a T-connection in the vent line (where the disintegrating valve used to be). I haven't done any research on this, but maybe someone makes a valve that can let small amount of air in (to reduce vacuum in the tank) and also provide a safety vent if the tank becomes overpressurized. Not sure such a beast exists, though. Maybe some emission related component would have this function, and it doesn't need to be Fiat-specific.

Or you could put two valves where the old valve was: one for the air bleed for the vacuum issue, and another for the overpressure vent.

-Bryan

[reidyyz]

My new plan:
https://www.summitracing.com/parts/hly- ... PPEALw_wcB

Remote vent maybe mounted where it protrudes near filler neck, under the fuel cap flap.

[reidyyz]

That is indeed ultimately what I did in the trunk:
Connected through a tee on the vapour return line with it poking through the skin beside the gas cap, new elex pump (as mech pump removed and blanked off long before I came along) new check valve (coming any day now), new flex lines throughout. And the tank external was cleaned and repainted, inside found clean as a whistle.
In the engine bay: filter installed (never installed before my time) on fabricated bracket secured to cool fan bracket and now a pressure gauge mounted on LH inner fender before carb to help with future troubleshooting.
I can't wait to put the fuel system back together as I keep smashing my head on the tank hanging in the garage. Yes, I hung it there, and yes, keep forgetting it's there and no, there's nowhere else to put it. Too. Much. Shit. in the garage