Leaky fuel cap

[Mark508f]

Hi
My touring seems to be blowing fuel back out of the petrol cap, I initially thought it was a problem with the filler neck but I have replaced that and the rubber boot, and I still have the same problem, and it definitely seems to be coming from the cap, is this likely to be solved by simply replacing the cap? Or is it more likely a sign of a blockage further down the line causing the fuel to vent out of the cap?
Any advice would be greatly appreciated.

Thanks

[Sambino]

I posted somthing similar! It was throwing pressure when I open up the cap. Like a hissing noise but no actual fuel. Not sorted yet but I changed my tank and fuel lines.

The fuel tank expansion tank houses in the wheel arch seems to be rattling on mine- may try new/ secondhand and see.

Did you catch any of the lines when you changed the filler neck? Is it actual fuel or fumes/gas

[Brianmoooore]

Doers this car have a cat., lambda sensor, etc.?

[Mark508f]

Yeah, it is fuel that's coming out, not loads but enough to leave a big streak down the side when I've driven it for a bit, I don't seem to have the pressure build up problem though, I'm thinking maybe the breather pipe is blocked as the cover plate is rusted right through and the pipe looks a bit squashed, I have a new pipe and cover plate on the way so hopefully that will solve it, will probably replace the cap while I'm at it.

The car did have a cat, it's a '92 316 touring, but I have recently put an M42 in it with a stainless exhaust without a cat, I did have the leak before the engine swap though.

Cheers

[Brianmoooore]

There would have been a carbon canister, fitted through a hole in the chassis rail structure behind the LH headlamp. What have you done with the pipes and wiring associated with this?

[Mark508f]

Not sure to be honest, I didn't do the conversion myself, how would that effect it?

[Brianmoooore]

, how would that effect it?

It's the sole vent point for the fuel tank, so if it's not been addressed properly, and left so that it is permanently blocked, it will give your symptoms.

[Mark508f]

Ok, thanks, will look into it

[Mark508f]

So, I have changed the breather pipe, which made no difference, haven't got a new cap yet but I have located the carbon canister, it appears to have been disconnected and the pipe on the throttle body has been plugged, the pipe coming from the tank is still connected to the canister and the outgoing pipe has just been cut and left about 2" long, there is a small amount of moisture underneath it which suggests some fuel has vented, is this ok? Or would I be better off just removing it all together and tucking the pipe up into the turret as suggested in the wiki?

[Brianmoooore]

Don't change the cap until this is sorted. If the cap seals as it should, and the vent is blocked somehow, the pump is capable of collapsing the fuel tank. Happened to me once, on a brand new car (Escort Mk 1), where Ford had left the tank sealed.
Ditch the canister, as per wiki, but before you tuck the hose away, check whether you can suck and blow through it with the fuel cap off, and get someone to check whether they can hear air hissing through the filler neck.
There should be no fuel in the vent line.

[Mark508f]

Ok, I'll give it a go, thanks for the advice