My car won't start, immediately after replacing a headlight bulb.

Big fire hazard, check all the connections to the fuel system.

Possible leaky fuel injector/regulator/fuel line. Possible disconnected/loose fuel purge/vent line. Possible leaky fuel filler tube or fuel tank. You will need to have the fuel system/lines inspected to determine source of smell. Not something I would put off as a major leak could develop and spill fuel on hot engine/exhaust causing fire

I would guess that one or more of the spark plugs, or spark plug (high tension leads) have failed. That would cause the engine to run uneven , off balance,and create fuel vapours due to unburned fuel.

Worse case scenario it could be leak on fuel injectors or fuel line, if possible have some turn engine over with hood open, if you can see or smell fresh fuel, get professional assistance as this is a extreme fire hazard.

Assuming there's enough fuel in the tank - If the fuel filter is extremely clogged - try starting with the fuel cap off so it won't have work against the vacuum in the fuel tank. Fuel caps have breather holes which can be clogged also. The holes release the vacuum in the tank slowly. If it starts ok then, the problem sits in fuel supply - for example the fuel filter.

Smell the exhaust pipe - if it smells strongly like petrol, most likely it's the ignition system requiring service. (sparkplugs, distributer, sparklines)

engines need 3 things to start (petrol engine)
fuel, air and a spark,
as you have been working on your fuel system it is best to suspect this system first,
on engine turn over see if you can smell fuel at the exhaust.
if you smell fuel the fuel regulation mybe too high and the engine is flooding.
if you do not smell fuel, remove fuel line from engine and ensure fuel is getting to the engine,
(be careful not to let fuel spill this generates a fire risk)..
once fuel is getting to the engine, check your ignition system to ensure you have a good spark to ignite the fuel.
finally check your air filter is not blocked and that you have air getting to the engine.

I hope this was helpful.

Car exhaust starts to smell bad (like rotten eggs) because of the sulfur content in the fuel and the catalytic converter not functioning properly. This can be a dangerous situation if the cat goes bad or gets clogged because they do operate at a very high temperature and if clogged can cause a fire. Run the car for awhile and look at the cat. If it is glowing red, turn the car off immediately (It's clogged), and don't drive it until the cat is changed out. Source(s):

sound like clogged fuel filter or faulty fuel pump.

If your exhaust smells like sulpher and the exhaust coming out of the tail pipedoes not stop immediately after engine is turned off. Your catalyctic converter is restricted. Have chk'd by muffler shop

does it have a cold start injector seperate from the other injectors usually on the upper intake somewhere with a fuel line going to it

There is a possibility that your timing belt has a couple of teeth missing now. When was the last time the timing belt was replaced? The reason for the fuel smell is the engine is trying to fire at the wrong time. It's trying to fire when the exhaust valve is actually opening. Replacing the belt isn't a bad job.