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petrol line may be leaking. The line runs underneath from the petrol tank to the engine. l had such a leak on my vauxhall and the heat from the exhaust ignited it. car was on fire underneath and burnt all the underseal away. Luckily enough there was a fire station about half a mile away and put it out in 2 minutes.

POSSIBILLY YOUR FUEL PUMP DEPEND ON WHAT MK IT IS ITS UNDER THE BACK SEATS UNDER A BLACK RUBBER COVER A PIPE MY HAVE SLIPPED OF

What year Astra? Can you see anyhting dripping underneath or under the bonnet?

If it is an Astra G model, the fuel cap rubbers get twisted and allow petrol vapour to come in through the windows.