New Fuel Lines Leaking; Pressure build up in tank

[FLGordie]

I changed the fuel lines under the hood of my carbureted 1980 Fiat Spider and I leaks at the carburetor return.. Ugh...

I used fuel line hoses and clamps 5/16" for the supply and 1/4" for the return. The mechanical fuel pump is not in circuit. Only a low pressure electric fuel pump. It leaks at the 1/4" return coming off the carburetor. The check valve is in the right direction. I blew compressed air 2" psi through the 1/4 hose and got air out of the tank. Put the cap on and the compressed air pressured the system and pushed fuel through the entire system and out the carburetor return inlet.

Update.. I changed back to the old hose clamps and the leaks stopped. Ran the car and at high speeds it is starved for gas. When I got home, I had a leak in the supply line right before the fuel pump. I opened the gas cap and the system was pressurized such that it shot out a splash of gas from the cap.

Does this indicate that a charcoal canister is clogged and not venting.



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[So Cal Mark]

your evap hose has a check valve under the car just in front of the rear axle. I've found 2 plugged valves on cars this week. That will cause pressure in the tank

[FLGordie]

Mark,

You have found a third! That was the problem. See picture. Completely plugged up. 12 years of sitting up old gas varnish.

Thanks for the solution.

[So Cal Mark]

that valve looks like an archeologist dug it up

[Fi8spider]

I'm experiencing the same issue where the fuel tank has started to build up pressure.
I have a 1974 which I imported from California. I installed twin 40 DCOE's many years ago and when I did so I plumped in the charcoal canister to the new intake system as per standard. I've never had an issue until recently.

I have searched for the check valve along the clear Cavis fuel pressure relief line and I have not been able to find it to see if that's blocked. The only thing I have found in the clear line is a 5/16 straight joiner in the trunk where the valve may have been removed by the PO and replaced with a plain straight joiner.

The one question I do have if anyone with a 74 can confirm is if the check valve as pictured above is found in the trunk?

BTW, if you are wondering. I have disconnected the line going into the charcoal canister and disconnected the line at the said joiner and tried to blow air through it but it seems blocked.

Cheers

[FLGordie]

It is located under the car in the return fuel line above the back axle driver side.

[PhillySpider]

I have heard what I thought was a slight inrush of air into the tank when opening the cap. Today filling up when I removed the gas cap air popped it off the fill neck high enough that it came down on the rear bumper and rolled across the ground! I had a look underneath before searching here and found what I thought was a fuel filter. I'll definitely be on the hunt for this thing tomorrow...anyone got a pic of a new one or link to purchase? Not sure from the fossil above what I'm looking for Thanks!

[spiderdan]

anyone got a pic of a new one or link to purchase? Not sure from the fossil above what I'm looking for

https://autoricambi.us/products/fuel-vapor-check-valve

[PhillySpider]

Thanks, found it! Just need to figure out how to remove it. I have some slack, should I just cut or does anyone know a trick to remove the clips and get the 40 year old barb fittings free from the hose?

[Ravq124]

I just removed my vapor valve and it was full of grey muck, can anyone explain the best way to clean it out?

[architect]

I just removed my vapor valve and it was full of grey muck, can anyone explain the best way to clean it out?

Simple. Toss it and buy a new one. They are cheap from the vendors