Checking your battery
Batteries are probably the biggest single cause for non starting, especially in colder weather. Batteries are less efficient the colder they get so the start of cold weather usually shows up any inefficiencies with the battery. Some of the time the problem seems to point to other things, i.e. the engine still turns over but doesn't fire up. Sometimes this can be due to the engine management system which only turns on the power to the coils if there is enough ampage left in the battery. If the power is too low then the ignition system is not powered up which leaves any power left in the battery to turning over the engine. Without the drain of having to power an ignition the engine turns over quite quickly and you could be forgiven for thinking that the fault lies elsewhere. Check you battery first. It's the most likely cause of non-starting faults and it is free and easy to check. Most common faults:
(1) Low fluid level. Most batteries these days are sealed 'maintenance free' batteries but if your battery has removable covers then you can inspect the level of the electrolyte fluid inside the cells. The inside of the battery is divided up into several cavities and you will need to inspect each one. When you look down into a cell you will see metal plates (Side on from the top). The level of electrolyte fluid should be higher than the plate for that cell to work. It will only take one cell to be low on fluid for your battery to show a fault. This fluid is dangerous and consists mainly of Sulphuric acid which is highly corrosive and should be treated with care. Luckily you do not need to add sulphuric acid to top up. Simply use distilled water (de-ionised) and top up the cell until the fluid is a couple of millimetres above the plate. Repeat for all cells.
(2) Poor charging from alternator. This is really up to a trained mechanic to diagnose and cure but you can test this yourself. A simple way to test if your alternator is charging is to start your car and put all your lights on full beam. When you rev your engine you should just be able to see the lights going brighter and then dimmer when you stop revving. If the car stalls when you put your lights on then the problem is probably with the alternator. Alternately if you have a test meter you can test the voltage to the battery. This voltage should be higher than 12V. Usually around 13-15V. Don't forget that alternators can overcharge aswell as undercharge which can produce the same type of non-starting faults by damaging the battery. This is usually accompanied with the smell of rotten eggs as the fluid in your battery begins to boil. Most of the time your alternator can be reconditioned rather then replaced.
(3) Incorrect battery fitted. Some mechanics will tell you that you need the exact battery for you car right down to the model, type etc. This is not true. You need the same size battery with the same amp/hour ratings. Of course the easiest way to make sure that you meet these criteria is to buy the exact battery for your car as quoted by the manufacturer (Replacing like with like) However if for some reason the battery has been replaced with a sub standard battery for your car then the above symptoms can arise and obviously replacing like with like will only perpetuate the problem. You can find out the required rating for your car's battery be contacting the manufacturer or dealer.
Bump starting: This can only be done with manual transmission and not an automatic.
Step 1. Get a few healthy lads to give you a push.
Step 2. Turn on the cars ignition and put the car into second gear.
Step 3. Make sure your handbrake is off and remove your foot off the foot brake.
Step 4. Making sure that your foot is on the clutch ask you helpers to start pushing.
Step 5. As the car reaches the fastest speed that you expect it to reach quickly lift your clutch pedal and press the accelerator slightly.
Step 6. If the car does not start then repeat these steps until exhausted. Then call a mechanic.
CARS WITH CATALYTIC CONVERTERS. Engine misfiring or bump starting can result in unburnt fuel being released into the CAT which then burns and causes sintering or meltdown of the ceramic monolith. However, jump starting using jump leads is permissible.
Car And Deep Cycle Battery
Frequently Asked Questions
What are the common causes of premature battery failures?
How Do I Test a Car Battery?
What causes my battery to drain overnight?
How do I charge (or equalize) my battery?