slant six cranks but won't start

I am going to check the distributor cap in the morning. I do smell gas under the hood and the plugs had a pretty good gas smell to them when I changed them this afternoon. I just don't understand how it can go from running to won't just that fast. It tries to catch when its cranking it even shakes the car a little, but never enough to full start. Thanks I'll post if I get anything out of it in the morning.