Fuel vent pipe / vented fuel cap

[rolemin]

Just wondering what folks thoughts are. I filled fuel tank up , drove 45 miles to a show, parked on pretty level ground, but as temp rose fuel spilled from centre of fuel cap, but stop a short time after removing cap. So is it a dodgy vented fuel cap or vent pipe , which I guess vents through cap.....your thoughts please, didn't happen in last summers heatwave.

 

[Piet]

it's a known problem. If you have a pocket of air trapped at top of tank on the LH side rear, i.e. RH side is lower, there is no air vent outlet on the LH side so as the air pocket expands it pushes the fuel up the filler pipe out of the cap. Avoid it by ensuring RH side is higher if you park with a full-ish tank on a hot day so air can bleed out. A fix would be to have an extra vent outlet on the LH side rear end plumbed into the existing vent, but that is too much trouble to go to. You need the right height of fuel, cold fuel warming up over hot ground, at exactly the right slope and having moved so you've captured an air pocket as you stopped. So it happens fairly rarely.

 

[Piet]

Meant to say not an issue with cap not venting, cap unlikely to seal and not a way it can happen. Would be caused more if tank vent blocked so worth checking the vent line is clear between tank and pipe. But there is still a way it can happen as outlined above.

 

[rolemin]

Meant to say not an issue with cap not venting, cap unlikely to seal and not a way it can happen. Would be caused more if tank vent blocked so worth checking the vent line is clear between tank and pipe. But there is still a way it can happen as outlined above.

Thanks will check