smell of gas(petrol) in the engine compartment,nissan ,maxima,1990
 

there is a smell of gas ( petrol) in the engine compartment, it seems to be coming from the area near the steering fluid resvoir ,what can be the cause?my car is nissan maxima 1990. so when I start my heater there is a smell of gas( petrol) inside the car. Its really bothering me. Please help