Thread: Fuel filler cap question

Originally Posted by CountP

1996 Disco V8.

Should my petrol cap have a Mitsubishi badge on? I only noticed it this morning. I would think not.

Could this be the reason why there is a vacuum in the tank each time I fill up?
On second thoughts maybe that's not such a bad thing. It might just slow the petrol gushing into the motor.

The cap is to hold petrol fumes from escaping, so you are hearing fumes ecape, not vacuum being released. Seeing as petrol remains the same regardless of which car it is put in a mitsubishi cap that fits properly is just fine.

Originally Posted by bee utey

The cap is to hold petrol fumes from escaping, so you are hearing fumes ecape, not vacuum being released. Seeing as petrol remains the same regardless of which car it is put in a mitsubishi cap that fits properly is just fine.

It's definetly a vacuum.
If it's supposed to have a breather in the cap and the Mitsubishi the cap came from has some other tank breather, surely that would be the cause of the vacuum.

Originally Posted by CountP

It's definetly a vacuum.
If it's supposed to have a breather in the cap and the Mitsubishi the cap came from has some other tank breather, surely that would be the cause of the vacuum.

Yes its possible, usually in icy cool weather only. Look at the centre of the inside of the cap. A correct cap will have a little spring loaded valve that lets air in with slight vacuum. If the mitsi cap doesn't have one just find a Holden/Ford one that does. Sucking gently on the valve should let air into the tank side.

Just thinking, if you are in Qld any vacuum would be generated by a failed purge valve on the charcoal canister. Worth investigating?

PM me if you want a used genuine LR cap, cost of postage only. I have 5 or so left over from dual fuel conversions.