Hi,

After filling up the tank (not brimmed) and some spirited driving I parken my car and noticed fuel gushing out of the filler neck.
I guess replacing the neck has just moved up the to do list (cap is already new) there seems to be al loose lockingring inside so now the cap can't lock itself.
What I was worried aboput was the fact that after removing the cap (I heard a venting sound) the fuel kept gushing out, so I put the cap back in and drove to a deserted spot to investigate...low and behold the gushing had stopped and the fuel level was at normal again.

Could this have been the fuel having backed up the filler because of my driving and not draining fast enough?
Is there a drain that could be blocked?

My Cinq used to do this but I never found the exact cause, I figured the problem might be due to there being not enough volume of air left in the tank to compress when very cold fuel (from the underground tank at the filling station) expands after being warmed by being in the car tank and being cycled through the fuel pump etc (unless I'm wrong I think unused fuel in the engine bay lines is returned to the tank).
I "cured" it by not filling the tank all the way up into the filler neck.
There isn't any drain to block,the filler goes straight into the tank and there is a smaller pipe that goes from the top of the tank to the filler neck top to allow air to escape as you fill with fuel (if this was blocked I'd expect it to blow fuel out when filling ?)

The only other thing I can think of is mine had an aftermarket filler cap and maybe the standard Fiat one has a vent ?

The OEM cap is an air tight seal, the vent is a pipe running forward into an aborptive receiver, which receiver is purged when the engine is running.

There may be a fault in the valves for the absorptive process.

It is unnecessary to brim a tank deliberatly, especially if the car is on a slope and the filler is on the high side, but I'd not have expected this to cause a problem.

Noel