Mondeo petrol tank | Technical matters | Back Room Forum

Mon 17 Jun 2002 17:41

Mondeo petrol tank - Onetap

SWMBO reported a smell of petrol when her 1996 Mondeo goes over bumps. There was no smell of petrol under the bonnet and no sign of a leak, so I thought that the petrol cap might be leaking.

There was no sign of a leak around the petrol cap, but when I unscrewed it there was a hiss of air under pressure rushing out (or it might have been in). The pressure difference was only slight (2 or 3 psi, I'd guess); the tank was near empty so there was a large volume of air. Is this supposed to happen? Every vehicle I've owned has had a vent for the tank somewhere. There seems to be an air inlet (or outlet?) valve built into the cap, and it seems to move freely. I'm not keen on having a petrol tank under any sort of pressure. Any ideas?

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Mon 17 Jun 2002 18:58

Mondeo petrol tank - jc

Not any longer;evaporative emission regulations require any vapour to be fed to a carbon canister which is then purged when you start the engine.The cap will seal so that vapour is forced(by pressure )to the canister.

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Mon 17 Jun 2002 20:36

Mondeo petrol tank - Keith S

Try the fuel gauge sender seal under the back seat.

The charcoal canister might have had a knock. It is plastic and in front of the petrol tank under the subframe.

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