If the car engine cranks normally but won’t start, at least you know that the battery and the starting system are working. If the battery was low on charge, the engine would crank very slow or wouldn’t crank at all; if the starter was bad, the engine wouldn’t crank. So let’s look at what else is needed for an engine to start and what are the common problems:
1. Compression in the engine cylinders. The normal compression in the engine cylinders is 120-170 psi. The engine won’t start if the compression is lower than 70-80 psi. The compression could be low for many reasons, such as a leaking head gasket, broken timing belt, incorrect timing, broken pistons, burnt or bent valves, etc. Often, overheating the engine causes the pistons to break or the head gasket to leak. In either case there won’t be enough compression in the engine cylinders to start. When the compression is low, it feels like the engine turns over unusually fast, like if the engine has no resistance.
2. Proper timing. The engine camshaft(s) that opens and closes the engine valves is precisely timed to the crankshaft through a timing belt, chain or gears. If, for example, a timing belt is broken or a timing chain got loose and jumped a tooth, the engine will not start or will run poorly. Another common problem is a stretched timing belt or chain. Often, in a high-mileage car the timing chain stretches causing the ignition timing to be too retarded to start. A stretched timing chain, for example, is a common cause of long-crank or crank-no-start problems in some 4-cylinder Nissan engines (Sentra, Altima).
3. Fuel and spark. A car engine needs proper air-fuel mixture supplied to the cylinders and a strong spark on the spark plugs in the right moment to ignite the mixture, so both the fuel delivery system and the ignition system must be in working order. Common problems with a fuel delivery system include a bad fuel pump, bad fuel pump relay or wiring. Another very common issue is when the car runs out of fuel, but a faulty fuel gauge still shows some fuel in the tank. A bad ignition coil pack and a faulty distributor are the examples of ignition system problems.
In addition, in a modern vehicle both the fuel-delivery and the ignition system are controlled by the engine computer. The engine computer in turn, is connected to the Transmission Control Module (TCM), Body Control Module (BCM) and a security system, so a problem with either of them can also cause the engine not to start. Here are few examples: a bad BCM (Body Control Module), defective crankshaft position sensor, defective security system sensor all can cause a no-start problem.
Did anything happen earlier that could cause the problem?
Sometimes, what happened before can give you a hint why your car won’t start. Let’s look at some common situations:
The engine was loosing power and died gradually, like if it run out of gas. It’s a common problem when the fuel level sensor doesn’t work properly and a vehicle runs out of gas while the fuel gauge still showing some fuel in the tank. A usual indication of low fuel level is lack of power that gets worse gradually. If there is a very little fuel in the tank, the engine may start and run for a short time, then die again. You may also notice that the engine chokes off when you press the gas. There is no way to check how much fuel left in the tank other than filling it up. One indication that there is no fuel in the tank could be the fuel pump that sounds differently. A fuel pumps typically runs for a few seconds when you turn the ignition on. In most cars, a fuel pump is installed in the fuel tank; it sounds like a quiet buzz coming from the back of the car. If there is no fuel, it may sound differently.
The car was repaired recently. If your vehicle’s engine was repaired recently, take it back to the repair shop and ask them to re-check it. Maybe they just forgot to re-connect some wire properly after repairs. This happens. For example, if yesterday you had your timing belt replaced and today a car won’t start, there is a good chance that something wasn’t connected back properly.
The engine won’t start after water got into the engine compartment. If your car died after water got in the engine compartment, for example, after washing the engine or after driving through a deep puddle, this could be caused by water shortening out some of the ignition components. Water could get inside the distributor cap or on the ignition coil and ignition cables and this could cause problems. Often this happens when a tune-up hasn’t been done for a long time. Take or tow your car to a mechanic to check it out. Often, once the ignition components dry out, the car may start again. If your car won’t start after water gets into the engine compartment, a tune-up is a good way to start.
A car won’t start after being overheated. Overheating the engine can cause a lot of problems and if the engine doesn’t start after being overheated it’s not a very good sign. Have your car checked out for compression in the cylinders. A leak down test also can help.
If you can get the engine to start, what helps?
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 to find a problem of this type 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, which is very common. 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 the security system.
Research common problems
If your car won’t start, there is a good chance that someone else had a similar problem with the same car as yours and already found a solution.
For example, if you search the NHTSA complaints at Safercar.gov for the 2002 Chevrolet Impala, selecting “Electrical System” you will find a number of no-start complaints related to the “Passlock” feature. Now, Google “Passlock” and you will find a number of treads at various forums describing the problem and ways to fix it.
By the way, searching online forums dedicated to a make and model you have can also be helpful in finding a solution for your problem.
You also can search Technical Service Bulletins (TSBs) for your car, if a similar problem already happened to other same-model cars, there is a good chance that the car manufacturer issued a TSB describing this problem.
Common no-start problems
A bad ignition coil could sometimes cause a problem where the engine cranks but won’t start in some 1996-2000 Honda Civic models.
The 2002, 2003 and some newer Nissan Altima cranks but won’t start. There is a couple of TSBs on this issue. One of the possible problems could be a bad camshaft position sensor (CMP Sensor). A bad crankshaft position sensor (CKP Sensor) is another possibility.
The 1998-2002 Honda Accord won’t start when hot, but start once cooled down. Sometimes a bad main relay (PGM-FI) can cause this problem. The main relay is located under the dash, near the steering column. A bad ignition switch can also cause a no start problem in this model Honda Accord. Some Acura models had the same issue too.
A bad crank sensor can sometimes cause a problem with some 90’s-00’s Jeep Cherokee when the vehicle would crank but won’t start. Some 90’s Volkswagen models (Golf, Jetta, Cabrio) won’t start after water got into the engine compartment due to a bad ignition coil.
