Tip & How-To about Cars & Trucks

Identify Vehicle Non-Starting Problems

P { margin-bottom: 0.25cm; line-height: 120%; } My car won't start. What's wrong?
This is a common question on Fixya and to be honest, quite difficult to answer for even the most gifted of mechanics. There's an incredible number of things that can cause non-starting.
It will not crank
Or is slow to crank or there is just a 'clicking noise' from the engine.

The first thing to do is check the condition and tightness of the battery leads. Bear in mind that if you disconnect your battery leads you will need to re-code the radio.

Check for corrosion on the terminals themselves. Corroded or dirty terminals can cause non-starting, as can a loose connection. You should also check the black earth lead where it connects to the engine block and/or bodywork. Clean and re-tighten it if need be. Something as simple as a 'bad earth' can result in these symptoms of non-cranking, slow cranking or 'clicking' noises.

Check the level in the battery (if possible) and if necessary, top up with distilled water until it covers the topmost plate in the battery.

A failing/failed battery will obviously cause these self same symptoms. Before you rush off to buy a new battery - don't! If your car will start with a boost, take it to a tyre/battery fitting workshop. They will test your battery in situ. If it isn't the battery at fault - maybe an electrical discharge from the alternator or instrument gauge - they will be able to identify it. Don't fit new parts in the hope that it will cure the problem - it usually doesn't. Save yourself some time, trouble and money by having things checked out by those who know what they are doing.

The workaround for checking your battery is to swap yours for a friends. If your vehicle starts ok and your friend has trouble starting..

It cranks over ok but won't start
This is where it becomes a bit more difficult ..

Was the car running ok before the problem started? Or did it cut out occasionally/slow down and then pick up revs? This is a classic sign of a failing fuel pump. Unfortunately for the home mechanic there's no way of testing the fuel pressure other than disconnecting a fuel line, switching the ignition on and hoping that fuel literally spurts out at pressure. Fuel pumps aren't cheap, but don't jump to the conclusion that it is the fuel pump at fault.

Some cars have a fuel pump in the tank to lift the fuel .. and another pump underneath the car to 'shove it' to the engine. In the most general of terms it is the pump in the tank that fails - because it is the one that does all the 'hard work'. But how do you make sure..?

Most non-starting problems are electrical - sensors.

There's coil (ignition) packs, camshaft sensor, crankshaft sensor, cold start sensor, airflow sensor ...

Everything plays its part to control ignition, fuel, airflow and ignition timing. Are you really going to replace one part after another in the hope that your car will start?

Unless you have diagnostic equipment there's no way of you knowing what 'error codes' are present. An error code gives an indication of what is wrong - usually a failed sensor.

The best way of sorting the problem out is to give a mobile mechanic a call, and ask him to run a diagnostic check on the car. Usually these guys are very good and have a 'feel' for things. Npay them, yes, and pay for then replacement parts/repairs ... but it's still cheaper than you buying replacement parts in the hope that it will cure the problem. It also saves a lot of stress.

If you're determined to sort the problem out yourself, begin by checking/replacing the camshaft and crankshaft sensor...

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Thanks for choosing FixYa and welcome. Below is a detailed list of everything you will need to check to find out why your car won't start.

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