Check your fuses: Few cars have a fuse associated with the starting system, but before you go monkeying around with everything, check your fuses to be sure it's not that simple.
Battery Corrosion: Over time your battery connections can become dirty, or corroded. This corrosion breaks the connection your battery has with the rest of the car, and it won't start. Try cleaning your battery posts and try to start the car again.
Dead Battery: The most common reason your car won't start is a dead battery. If you have a battery tester that can measure cranking amps, test your battery to see if it's weak. If you can't test it yourself, you can test the battery indirectly by jump starting the car the car. If it starts right away, your problem is most likely a dead battery. Replace the battery, and clean the battery connections to ensure good contact.
Bad Igntion Switch: If your battery checks out, but the starter is still silent, it may be a faulty ignition switch. Turn the key to the on position (not all the way to start). If the red warning lights on your dash don't light up (and your battery connections are clean), the ignition switch is bad. If they do light up, turn the key to the start position. The dash warning lights should turn off at this key position (most cars). If you're not sure, turn on the headlights. When you try to start the car, the lights should either dim (a lot) or turn off completely. If they do, your ignition switch should be ok. If not, the switch will need replacement.
- Bad Starter Connection: Corrosion can not only keep your battery from connecting, it can affect any electrical component, especially the ones exposed to the elements like the starter. If you have a helper, you can test the connection by holding a circuit tester lead on the wire that engages the starter. This is the smaller of the two wires connected to the starter. Be sure no part of your body is near the moving parts of the engine - it could still start at any time! Have a friend turn the key and check the current. If you're getting current to the starter but it ain't spinning, it needs replacement.
With the starter-related causes of your no-start problem out of the way, we continue the search for why your car won't start. If the engine can't get spark, there will be no fire. But don't crawl into the hole just yet. Spark is created by your car's ignition system (ignition means "to ignite). Ignition system troubleshooting isn't too difficult when you're looking for a no-start problem. The first place to check is your coil.
- Coil Testing: To properly test your ignition coil you'll need a multimeter that can measure impedance. If you don't have a multimeter, there is an easier test you can perform using simple hand tools. Test your coil and, if it's bad, replace it.
- Distributor Cap: Your no-start problem probably isn't caused by your distributor cap, but occasionally, especially during wet weather, a faulty cap can keep your car from starting. Remove your distributor cap and check the inside for moisture. If there is even a drop or mist of water inside, wipe it out with a clean, dry cloth. Inspect the cap for cracks and replace it if necessary. Once its dry, though, it'll work.
- Coil Wire: The starting problem could also be due to a broken or shorting coil wire. Inspect the wire to see if there are any obvious cracks or splits, then test for continuity using a circuit tester.
If the starter is spinning and the sparks are flying, your no-start problem has got to be related to the fuel system. If your vehicle is fuel injected, there are a number of sub systems that could be the culprit. It will take some serious diagnostic work to figure it out, but there are some things you can check in the garage that will narrow it down, and could save you some money by avoiding a trip to the repair shop. Here are some things to check:
- Electrical Connections: There are plenty of electrical connections in your fuel injection system. Each fuel injector has a connector on top. There are connections on the air side of the intake and on the cylinder heads. Basically you should check every electrical connection you can find under the hood to be sure it's tight.
- Fuel Pump and Relay: To check your fuel pump, you can do a fuel system pressure test - if you have the equipment. Since most of us don't have that type of thing, we'll first check the electrical connections. Test the positive side of the fuel pump for current with a circuit tester. Be sure the key is in the "On" position. If there's current, move on to the next step. If not, you should check the fuse. If the fuse is good, your problem is the fuel pump relay.
- Fuel Filter: If the fuel pump is working properly and fuel is still not reaching the engine, the problem could be a clogged fuel filter. You should be replacing your fuel filter every 12,000 miles or so anyway, so if you suspect it could be clogged, go ahead and replace it.
With the major systems checked out, there are a number of other things you can check to see why your car won't start - if you have the patience.
- Loose Starter: Loose starter bolts will cause it to dance around and wiggle, failing to turn the engine over.
- Bad Injectors: A bad injector can throw the whole fuel system off and keep the engine from firing, especially when the engine is warm.
- Faulty Cold Start Valve: A failed cold start valve will keep your car from starting when the engine is cold. It can also malfunction and keep your car from starting when it's warm!
- Chipped Flywheel or Ring Gear: Your starter's gear connects with the gear teeth on your flywheel or ring gear (depending on transmission type). If one of these teeth becomes worn or chipped, the starter will spin. You'll hear loud screeches, scrapes, squeals and grinding if this is the case.
- Bad ECU or MAF If your engine's main computer or any part of the system's electronics go bad, your car won't start. Unfortunately you'll need to leave this type of diagnostic work to a qualified repair shop.