What do you do when your car will crank but not start?
Cranks but won't start:
In a situation like that I always tell people to go back to the basics: Spark, fuel and Compression. If you have all three, it should start. The spark has to be at the correct timing, but if the vehicle was running and suddenly stopped, there isn't much reason to believe that the timing changed. The fuel has to be delivered in an approximately correct quantity for the engine to run right but it should at least pop and attempt to start. So... Start with fuel. Using starting fluid, spray in the throat of the throttle body while a friend attempts to start the engine. If the engine runs while you're spraying, you probably have a fuel problem. Check the fuel line for pressure. If you don't have any it's probably the fuel pump. It's in the tank and you'll have to drop the tank in a suburban to get to the fuel pump. It isn't as bad as it sounds. Disconnect the battery first. Siphon out as much as you can get easily, disconnect the fuel fill pipe from the tank, using a floor jack, support the tank while you remove the straps. There are usually only two. Once the straps are disconnected, lower the tank and remove the fuel line and the wires to operate the fuel pump and fuel gague. You'll have to clean the top of the tank so that you don't get debris inside, then remove the screws and work the pump assembly out of the tank. On the other hand... if you have fuel pressure and the engine doesn't start when you use the starter fluid, you probably have a problem with ignition. Pull one spark plug wire, then using a spare plug from some other source, attach the wire to the spare plug and lay the plug on a metal part of the engine, then crank the engine and watch the plug. If you have spark it might be something else. If there is no spark, find out why. It could be the pickup coil, electronic ignition module, high voltage coil or even a bad rotor in the distributor. It's all a process of elimination. Remember the words of Sherlock Holms, "When all other possibilities have been eliminated..."
Could be flooded (especially if carbureted), you could have a wire disconnected if you've been messing around under the hood, or there could be humidity in the distributor.
A common fault is the Crank Position Sensor (CPS).
This is an induction coil mounted just above the crank pulley.
If the tachometer does not register at all during cranking, the CPS has probably failed.