1991 Jeep Cherokee Starting

I have checked the Plugs, Dist Cap, etc but the car turns over for ages before starting regardless of wether it is hot or cold. I wondered if it could be a petrol supply problem because after stopping the other day there was a strong smell of petrol, but a search underneath has not found a leak, however when it is parked facing downhill when you first switch on the petrol pump ticks for a short while! The car runs very well normally and as yet has not let me down.