Typically those symptoms are a leaking check valve. Not too familiar with your car but it’s usually screwed on the pump or filter. I’d definitely search around for that gas smell.. leak or cracked vent hose somewhere

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1993 e300
1995 e320
1994 e320
2006 s500 4matic
2004 Jeep wj overland
2001 Ducati 748
2004 Honda shadow aero