Why is there a gas smell?

Hi Ed.
this is all i could find at the moment.
Gas Cap Causing Gasoline Smell in Car. I know it may seem obvious, but a loose or missing gas cap can cause a fuel smell in your vehicle. You could even have a faulty gas cap that is leaking fumes. A faulty gas cap can also cause the check engine light to illuminate with a DTC on newer cars.

Gasoline Smell in Car, 5 Common Causes - Simple Car Answers

or go to this link and read up some more.
Smelled gas and check engine light came on Google Search

Me too, but I think it's the beer and chili had for lunch. It'll eventually go away.
Seriously, you need to post more than this. Give us the make, model, year and engine, and some details - when do you smell gas? When it's running, after you shut it off, inside the vehicle, etc.

Raw gas smell may be the culprit of starting noise. Leaky injector(s) could be causing some fuel to enter chambers as you shut off engine, washing oil off cylinder walls and diluting oil. Check fuel pressure key on/engine off and test for gas in the oil.

IT IS LOOKS LIKE A FUEL PRESSURE LEAKING INSIDE THE ENGINE OR DEFECTIVE FUEL INJECTOR LEAKING . TRY DISCONNECTING THE FUEL PUMP RELAY. AND CRANK THE ENGINE IF ALWAYS CRANK WITH OUT OF FUEL (CRANK WITHOUT START) YOU HAVE FUEL LEAK INSIDE THE ENGINE
REMOVE THE INJECTORS RAIL UP EVERYTHING CONNECTED,PUT BACK THE FUEL PUMP RELAY TURN THE SWITCH ON AND FIND WICH ONE IS LEAKING. (GASOLINE IS FLAMMABLE TAKE CARE)

what yr and make is this vehicle?

Most likely causes are bad engine coolant temp sensor OR leaking fuel injectors. Bad engine coolant temp sensor will give computer false reading and computer provides wrong air fuel mixture. Leaking fuel injectors will load the engine with raw gas--just like flooding it. Try pushing the gas pedal to the floor and holding it there when cranking when hot. That forces the computer into "clear flood" mode and it shuts off the injectors. If it starts up with pedal down, that would be a sign of leaking injectors.

The chain could jump a tooth or two, but normally a chain or gear breaks. You could pull the spark plugs and check compression to find out.
It sounds like one or two injectors may have failed allowing liquid gas to flow into the cylinders.

gas is a very high evaporative liquid..fumes extremely strong..if overfull it will smell..and if emissions equipment has issues it will smell also.. when the engine gets hot, any gas present will vent off until the engine cools..thats the fuels evaporative nature..still keep an eye out for issues..

sounds like it may be the catalytic converter

you have either a blown head gasket or cracked head. The white smoke is coolant passing through the engine and exhaust. The gas smell is from compression leaking past the gasket or head, pushing fuel vapor into the air.