Technical Fuel tank builds pressure in sun

[Slotman]

Had an odd thing occur yesterday...temperature was 90 degrees, or 32.2 C and my 79 spider was parked outside all day in the sun to clean out the garage, started it,and moved it around several times and it ran great, my spider was a California smog car and all the emission equipment was either removed and gone. or disconnected when I got the car years ago, the only vacuum sources coming from the intake are to the distributor, and to the vacuum modulator, (auto trans), there are no other open ports, I have an aftermarket 32/36 weber that only has a line in for fuel, no hook up for the fuel tank return line, it's currently capped off, the carbon canister is still fully hooked up and I assumed that would still allow the gas tank to vent..but i smelled fuel although none was leaking until I removed the cap on the tank return line, once I did that an occasional drop of fuel would drip out...then when I opened the gas cap quite a significant amount of air pressure leaked out so it seems the tank was unable to vent sitting in the sun..shouldn't the tank be venting thru the carbon canister? As I mentioned it's still fully hooked up....the gas cap itself is not vented is it? I realize my suitation is a bit complicated due to the emission equipment being removed but it seems like the fix for this should be fairly easy? What would be the best way to insure the tank is venting? This issue possibly must have came up with others running aftermarket carbs with the smog stuff gone...thank you in advance for any advice!
Cheers! Terry
.

 

[ZaphodB]

Try this https://www.tanksinc.com/index.cfm/...KtOvD549a92u7aEabq06cddKzdHB0s598T7-uqyNJtuSN

A carriage return/line feed/paragraph from time to time might make your message more readable.
Couldn't even see the question for a while.

 

[Slotman]

I do tend to ramble sometimes....my goal was to present all the relevant facts for the problem, perhaps I should have asked the question first, and then done so.
I'm sorry for making my question difficult to read...haha as in recall I only got a "C" grade in English class and P.S. thank you for the helpfull info!

 

[ZaphodB]

Had an odd thing occur yesterday...temperature was 90 degrees, or 32.2 C and my 79 spider was parked outside all day in the sun to clean out the garage, started it,and moved it around several times and it ran great.

My spider was a California smog car and all the emission equipment was either removed and gone. or disconnected when I got the car years ago, the only vacuum sources coming from the intake are to the distributor, and to the vacuum modulator, (auto trans), there are no other open ports.

I have an aftermarket 32/36 weber that only has a line in for fuel, no hook up for the fuel tank return line, it's currently capped off, the carbon canister is still fully hooked up and I assumed that would still allow the gas tank to vent..but i smelled fuel although none was leaking until I removed the cap on the tank return line, once I did that an occasional drop of fuel would drip out...then when I opened the gas cap quite a significant amount of air pressure leaked out so it seems the tank was unable to vent sitting in the sun..

Shouldn't the tank be venting thru the carbon canister? As I mentioned it's still fully hooked up....the gas cap itself is not vented is it?

I realize my suitation is a bit complicated due to the emission equipment being removed but it seems like the fix for this should be fairly easy? What would be the best way to insure the tank is venting? This issue possibly must have came up with others running aftermarket carbs with the smog stuff gone...thank you in advance for any advice!
Cheers! Terry


FYI That would read better, just split it up into easy chunks, just trying to make you write your next question betterer
Just taking a breath/enter key between chunks

 

[Slotman]

Wale, I done try to be betterer next time! Sorry!

 

[Slotman]

Just kidding around! What I love about this forum is that its international, there's not always going to be proper English, there's going to be miss spelled words....
Personally my goal is to learn as much as I can, give back when I can, and focus on the automotive aspect of the topic ...again I thank you for your help!

 

[ZaphodB]

Just kidding around! What I love about this forum is that its international, there's not always going to be proper English, there's going to be miss spelled words....
Personally my goal is to learn as much as I can, give back when I can, and focus on the automotive aspect of the topic ...again I thank you for your help!

That vent I linked to wasn't expensive, let us know how you get on

 

[124BC1]

FOR THE BENEFIT OF ZaphopB, I've tried
using carriage return and dividing the fo
llowing text into paragraphs, I hope it's
to HIS liking...

Assuming you're talking about the carbo
n canister installed in the engine bay?...

I seem to recall that those carbon fuel va
p or canisters had to be replaced at som
e set interval i.e. they're a service item?

I've seen mention on this forum of some
new owner's of 124 Spiders finding that
someone had punched a hole in the top
of the carbon canister instead of
renewing it, suggesting that it perhaps c
an become blocked up /choked in servic
e?

And if there is no longer any vacuum con
nection from the engine to this carbon
canister on your car, and gas vapors we
re to vent from the gas tank up and into
the canister, could the vapor condense i
nto liquid and be trapped inside the can
ister without nowhere to go?

 

[Slotman]

As always, thank you sir for your wisdom, and great advice! .
Also in this case your most excellant sense of humor!
I'm thinking you nailed it with the fact the original lines are still hooked up from the tank but the vacume to the canister no longer is.
I was just wondering how those that have removed the smog stuff and modified things such as carburators, handled this..
Thanks!

 

[124BC1]

Maybe they just fitted an older vented gas cap or...

punched a hole in the carbon canister and let it breathe the fumes to the atmosphere

 

[Slotman]

Hi all, a closer observation today revealed there's about 6 lines running out of my California ex smog cars gas tank, 2 are the gas feed line, and the return line, the others I doubt are doing much of anything,

Breath

At the carbon canister there's 2 lines in at the bottom, one is directly from the gas tank, and the other is an open line that likely went to smog stuff, it's currently open and vents higher than the carbon canistor,



There's slso an open line from the top of the canister so my point is it appears to be vented top and bottom yet still the issue occurred.



I'm going to try first at the gas tank filler neck pipe where there's the "spud?" ( metal in line) welded on just below the gas cap, with a rubber hose that goes to ? , to vent it as high as possible with some kind of baffle/ filter and see it that keeps the pressure from building in the sun...

Hopefully I done typed this betterer


Will update !

 

[Jockstrap]

I'd a Toyota MR2 Spyder which had the Evap system disabled/bypassed. YouTube has some videos originally from USA which will help with routing.
The charcoal cannister should be serviced to function properly. If clogged back pressure in the tank. A top hose returned to the engine intake.

I removed the cannister and vented with a motor bike tank vent into the wheel arch.

The electrical connection remained in place to keep the ECU happy.

Interesting reading if you look for CEL P0440 code.

 

[Slotman]

Thanks for the advice jockstrap! I'm going to do something similar from under the car near the filler neck, mounted as high as possible that will let air escape but hopefully not slosh gas.

Also I will try hooking the canister top line thats currently open, to a vacume source and try and figure out if the canister is even working.

Perhaps in my case there's a better way than keeping the canister but if it's working or can be made to work again I would like to keep it. Terry

 

[Jockstrap]

Look at motorcycle breather online valves. Designed to avoid fuel spillage especially if you turn turtle .

Have fun.

 

[124BC1]

@Slotman : re. the connections at the gas tank and charcoal filter...

I believe you have a copy of the Pininfarina Spider Service Manual?

I don't have one but I did read it (all c. 627? pages ) last night
on the archive.org website I mentioned in post #5 on another thread -

Can You Help Me Identify These Parts | FIAT 124 Spider (Classic)

These three parts were included with the purchase of my 1978 Fiat 124 Spider 1800. I don't know what they are or where they go in my engine. Can you help identify them and their location? Thanks in advance.

www.fiatforum.com

sadly the pics and print were poor resolution so I had to keep magnifying
them in order to decipher any interesting pages/pics and they didn't
include copies of the fold-out pages...

Anyway, if you check out 102.01 Page 10-81 in this manual you can
see how all these tank and charcoal canister lines were originally
connected and then maybe figure out what might now need to be
re-connected to cure the recent issue with the gas tank not venting.

I did notice there are also some 'check-valves' in the system....

 

[124BC1]

Assuming you're talking about the carbon canister installed in the engine bay?...

I seem to recall that those carbon fuel vapor canisters had to be replaced at some set interval i.e. they're a service item?

I've seen mention on this forum of some new owner's of 124 Spiders finding that someone had punched a hole in the top of the carbon canister instead of
renewing it, suggesting that it perhaps can become blocked up /choked in service?

And if there is no longer any vacuum connection from the engine to this carbon canister on your car, and gas vapors were to vent from the gas tank up and into
the canister, could the vapor condense into liquid and be trapped inside the canister without nowhere to go?

I came across this schematic of the Fuel Vapour Recirculation System used on some Fiats - it seems the 3-Way Valve includes a safety function to vent excess vapor pressure in the tank to ambient in the event that there is a blockage in the vent pipe to the canister. It also shows what is inside the charcoal canister including 3 types of filter, this suggests it has to be replaced, rather than be serviced.

Of course this info may be very different to what remains of the 'smog' gear on your particular car but it might give you some idea of where to check to sort out the issue with the fuel tank building up pressure.

 

[Slotman]

124bc1, thank you! , I will look for the 3 way valve back by the tank, I wouldn't be surprised if it's not there though, I'm pretty sure it's not in the engine compartment.
It's easy to see the lines where they come out of the tank, but trying to see where they go, especially from the engine compartment end gets tricky.....
I'm going to start with the line that's still in place between the tank and canister by first looking if there's a one way valve, then trying to check for a blockage, next might be tearing in to the canister to see what makes it "tick" ....if I can't get it figured out I might need to see if I can make some kind of simple vent myself like "macGyver" might do, I drove the car several hundred miles before I parked it for those years and it didn't seem to have the problem then, perhaps it's another one of those things damaged by sitting...