What is needed for an engine to start?
First, let's see what normally takes to start a gasoline car engine:
1. The engine must be turned over by the starter motor with enough speed to catch. For this to happen, the battery must have enough charge, the starter motor and the starter circuit should be OK.
mixed with air in the correct proportion must be supplied to the enigne cylinders;
- there must be a strong spark at the proper moment to fire the air/fuel mixture.
4. Proper timing
- the engine valves should open and close in appropriate time.
- normal compression in the cylinders is 120 - 170 psi. The engine won't start if the compression is lower than 70 - 80 psi.
If the engine won't start - there's no magic - one of these things is probably missing. Sometimes the problem could be very hard to find, for example, when it doesn't happen at all the times. Often, though, it could be something very simple, like a dead battery If a car doesn't start sometimes, but not all the times
Sometimes a car may have an intermittent problem, when it starts fine most of the time, but once in a while it doesn't. Such problems, that are not presented at all times, could be very difficult to diagnose. What will help your mechanic to find such an intermittent problem is if you notice when, under what conditions the car doesn't start and what helps to get it started. For example, if you notice that wiggling the ignition key helps to get the car started, it may tell your mechanic that the problem is likely with the ignition switch (very common problem). Or if the security light flashes on the instrument panel each time the car doesn't start could tell your mechanic to begin with checking anti-theft system. The key won't turn in the ignition
If the key won't turn in the ignition, it could be for a couple of reasons: Often this happens when the steering is locked by the ignition lock with the front wheels turned aside (e.g when parking on a hill) or when one of the front wheels is pushed against something (e.g curb stone). In this case, try turning the steering wheel left and right while gently jiggling the ignition key - this might help.
Another possibility is that there is a problem with the ignition lock or the key itself. This happens, the key and the lock mechanism wear over time. Try to use a spare key. If nothing works, your local dealer is the best place to call. "Security" or Key-shaped light flashes on the dashboard
Many cars these days are equipped with an immobilizer. (you can find more information about the immobilizer in your owner's manual). The immobilizer allows the engine to run only if the correct key is used. If your car has an immobilizer, you probable see a "Security" or Key-shaped light coming on on the dashboard every time you turn the ignition ON. If this light is flashing when you turn the ignition ON, it could mean that there is some problem with an immobilizer or the system does not recognize the key. If the immobilizer doesn't recognize the key, the engine wold not start at all, or would start and then die in few seconds.
You can try a spare key, if it won't work, your dealer is the place to call. Sometimes, the key is just need to be reprogrammed. On some cars you can find the information how to reprogram the key in the owner's manual. The starter won't crank
If nothing happens when you turn the ignition key to "Start" position, means that the starter motor doesn't turn over the engine. Most commonly this could be caused by a dead battery.
However, if the battery is OK, but the starter still won't crank, there could be a number of possible reasons. Here are some of them:
- The ignition switch could be at fault - it's a common problem.
- The starter motor itself is common to fail.
- Starter motor control wire could have bad connection.
- Cars with an automatic transmission have a Neutral Safety Switch that allows the starter to be operated only when the transmission is in "Park" or "Neutral" position. When this switch isn't functioning properly, or for example, when the shifter is not fully engaged in "Park" or "Neutral" position, the starter also won't crank.
- Similarly, cars with manual transmission have a switch installed at the clutch pedal that only allow the car to be started when the clutch pedal is depressed. The problem with this clutch pedal switch could also prevent the starter from operating
- A problem with vehicle's security system or some other electronic control module (e.g, PCM, BCM) may also prevent the starter from operating. The starter cranks very slowly, the engine won't start
This also might be caused by weak or discharged battery.
If the battery is OK, starter cables could have bad connection or the starter motor itself could have a problem. Another reason, the engine could have an internal problem (e.g, lack of oil, very old engine oil, etc.) The starter cranks normally, but the engine won't start
At least you know that the starter is working. If the starter cranks but the engine won't start, there could be wide range of problems. Here are some of the most common:
- Problems with fuel delivery system (e.g bad fuel pump, fuel pump relay, clogged fuel screen, etc.)
- Problem with engine electronics (e.g crank sensor, cam sensor, air flow sensor, power relay, engine computer, etc.)
- Ignition system problems, especially on older vehicles with the distributor (e.g bad ignition coil, commutator, rotor, distributor cap, etc.)
- Defective ignition switch
- Problems with vehicle security system
- Internal engine problems (e.g broken timing belt or gear, low compression, etc.) Battery problems
Discharged or dead battery is one of the possible reasons for a car not to start. Very common is the situation when we forget to turn the lights off overnight (the dome light, for example), which causes the battery to drain. In this case when attempting to start a car, all you will probably hear will be a clicking noise - there won't be enough power to turn the starter. Here is the simple way to check if the battery is discharged: Turn the ignition on. With the engine off, turn the windshield wipers on. If they move way too slow, much slower than usual, the battery is probably discharged. Also look at the dashboard lights - if they appear very dim, the battery is probably discharged.
If the battery is relatively new, it can be recharged. All you need to do is to boost your car and let the engine run for a while to charge the battery.
However if your battery is more than three-four years old, you will probably need to buy a new one. Sometimes, an old battery may even die with no apparent reason, even if the day before it was OK. The engine won't start after water got into the engine compartment
If you car died after the water got in the engine compartment (after engine shampoo or after driving through deep puddle), this could be because some of the ignition components could be short-circuited by water. Often this happens when a tune up hasn't been done on the car in a long time. Take or tow your car to a mechanic, he (she) can check it. Often a simple blow drying the engine can help if there is no other damage. Your mechanic could also recommend a tune-up to prevent this from happening. Engine noises
Heavy knocking from the engine most likely points out to the severe engine problem - for example when the engine runs out of the oil.
Whistling may be a result of a loose drive belt. When the drive belt is loose, it slips on the alternator pulley, which causes the alternator failing to recharge the battery.
Engine detonation pinging (High pitch metal knocking that appears mostly while accelerating) is usually a result of poor gasoline. It also may happen when one of the cylinders misfires or when the engine overheats. Happy Driving!!! Source