Possibly the catalylic converter.
Your fuel system might have a leak if the strong smell is similar to the smell of refuelling. Or the exhaust might have a leak allowing fumes to get in the cab with you. Diesel fuel has a strong oder if burnt in a rich mixture an in under hard acceleration.
One thing could be an over used belt or a leak of antifreeze
Check out the top of the fuel tank and the tubes leading to it.
I would think that you have a rusted fuel line that is leaking. It is very common in older (10 +)vehicles. You should find the source of the leak and replace the fuel lines. Get a knowledgeable mechanics advice.
You should never smell fuel from a fuel injected vehicle. Fuel leaks can be dangerous and should be repaired as quickly as possible.
you probably have a leak that drains your pressure when it sits, and that's what you smell. it is not safe to drive with a fuel leak
Hoses going into the fuel tank are probably old and cracked. Check under the car for any sign of wet spots around the hoses and on the tank. Also around the filter. Then start the vehicle when its cold and let it run about a minute, not too long you don't want it hot. Then open the hood slowly and smell around. If the engine compartment has a strong gas smell you could have an injector seal leaking.
There are many causes for a car not to start. One of the causes can be the fuel pump which pumps fuel into the carburetter to spray into the ignition chamber.A bad pump may not pump the fuel into the carburetter .
I had the same issue about two weeks ago. Turns out the fuel return was the problem.
Check plugs and wires/fuel injectors/fuel filter
It might be coolant, oil burning or too rich of fuel air mixture
The strong fuel smell could possibly be coming from the evap canister from inside the engine compartment. If the canister is not purging at the correct intervals than it will back up into the engine compartment and even possibly stall after awhile.