[davew]

I have a US spec Spider S2 1976 which has a smell of fuel in the trunk
This is due to small a vent pipe in the downtube from the filler cap (On the right below the nut)
Looking at the FAQs I assume this was part of a sealed system originally
I can't block it as this causes a vacuum - Should I vent it outside with some tubing?
Thanks
David

 

[yvesmontreal]

That might be an idea. Originally, there was a vinyl tube connected to a black plastic canister attached on the left side of the trunk; a T fitting is connected to a check valve, and another tube runs from the canister to the intake manifold. Usually a sticky or broken check valve is the cause, but now your tank is breathing in the trunk! It must be especially bad after you fill up the tank.

Another solution would be to block it AND use a vented cap. Or maybe just a check valve to let the tank suck in air as fuel is being consumed by the engine?

 

[spiderserie4]

I have a US spec Spider S2 1976 which has a smell of fuel in the trunk
This is due to small a vent pipe in the downtube from the filler cap (On the right below the nut)
Looking at the FAQs I assume this was part of a sealed system originally
I can't block it as this causes a vacuum - Should I vent it outside with some tubing?
Thanks
David

so you have converted the spica to carbs and got rid of the entire vapour system?

then, yes, just vent that outside, or block it and use a vented cap as Yves suggested.

the big filler boot also has a drain that exits out the trunk, this is sometimes split just as it exits, so then if you fill the tank and spill a bit, you get raw fuel trickling into the trunk. (Plus it is a drain for water)
worth checking that too, see here:
Fuel Filler boot drain

 

[yvesmontreal]

The drawing in the previous post remind me the canister is connected to a second bib directly on the fuel tank, towards the front of the car, at the base of the fuel filler on may GTV. This might have been left opened as well.

 

[davew]

Thanks for your replies
Yes, the spica is gone and the car is running on twin Dellortos - it was like this when I bought it
Looks like the easiest option is to use a vented cap and plug the vent pipe - Can the existing fuel cap be modified or will I need a replacement?
I'll also look into the other points mentioned
Thanks
David

 

[yvesmontreal]

I don't think the cap can be modified without perpetuating the problem - if you drill a hole in it, you will have an opening to the tank within the trunk. If you have the bayonet cap, compatible vented caps exist - I have one, but I found it at a gas station and have no idea what car it is supposed to fit. Bring the sealed cap to a parts retailer, maybe he'll have an eye for something.

If you have the thread cap, it's going to be hard. The solution would be, as you said first, to install a tube going outside.

 

[yvesmontreal]

Check this thread....

Note that using an open vent can end up in a fuel spill if the car flips on its side. 😵