What to do if your car doesn't start (2)
Step 2: Checking the Electrical System
About Push Starts:
A push start may or may not work with the problems listed below. Do note that a push start won't get you anywhere if your battery is completely flat and the fuel delivery system gets no power. As an example, check this threadout. Also, not all cars can be push started; check your owner's manual for details.
The commonest culprit at the root of preventing your engine from starting up, or that caused it to die suddenly, is the electrical system. Turn on the ignition switch, but don't crank the starter. Are all the telltale lights on the dashboard coming on & fully illuminated?
If YES (all dashboard lights are on):
Determine if the battery has enough charge to be able to start the car. A quick way to check is to turn on the headlights and blow the horn. If the lights dim and the horn sounds hoarse, you have a nearly flat battery. It's push-starting or jump start cables to the rescue!
If there are absolutely NO telltale lights on the dashboard:
A completely drained battery (did you leave your lights on last night?). Time to bring out those jump start cables and hook up to an obliging neighbour or friend's car. Read this Related Thread and Related Post. A neat video:
A loose connection at the battery terminal (check if the terminals are tight, or if there is excessive corrosion).
A blown main fuse. Check your owner's manual to locate the main fuse. Replace the fuse (if you have a spare) and try again.
Be prepared that the fuse might blow again, in which case there is a short circuit somewhere and you need to summon professional help.
If the starter motor is turning over, but is slower than normal:
Your battery has low charge. You may start the car with a push-start or call for assistance from those jump start cables. No point in persistently trying to crank in the hope that the engine will fire because it usually doesn't, and the battery will run down completely.
If there is no noise from the starter at all:
Some cars won't crank unless you depress the clutch pedal fully, or shift the transmission to 'neutral' or 'park' position. Silly mistakes happen to the best of us.
If you do not hear a clicking sound from the starter solenoid (relay) when you attempt to crank the engine, you may have a defective starter solenoid, and the starter motor isn't getting any current at all.
The starter motor cable may have come loose (no contact). Tighten and re-try to start the car.
Your ignition switch is burnt out (older cars) or faulty.
If you hear an audible "click", but the motor doesn't turn over:
The starter motor solenoid (relay) is actuating, but the Bendix gear is perhaps jammed up against the ring gear. Place the car in 3rd / 4th gear and push / rock the car backwards to release the Bendix from the ring gear. You'll hear an audible click as the car moves backwards a little, in case the Bendix has actually jammed against the ring gear (usually caused by broken/worn teeth in the Bendix or ring gear). Try starting the car again. Warning: DO NOT hold the key in "start" position for too long if you hear the click and the starter motor won't turn. It'll burn out the starter armature windings.
A loose connection on the starter motor cable - not enough current getting through for the starter to turn.
Starter motor brushes worn out.
Check and tighten the contacts, and tap the starter motor body with a heavy stick or rod. Watch the following video, especially from the 1:28 point onward.
If the starter motor churns over normally, but the engine will not fire:
A push-start won't help in this situation.
Your central locking / security system may be intervening by cutting out power to the ECM. Reset the central locking system and try again.
Some cars have a fuel cut-off inertia switch. If someone had rammed your parked car, it could have triggered the inertia switch to cut off the fuel supply. Check your owner's manual for details on resetting the inertia switch.
For petrol engines : No spark at the plugs. The HT coil may have failed. For older distributor-type engines, there could be moisture in the distributor cap, or a fouled set of contact breaker points. For newer engines, OBD may be needed (i.e. hooking up a laptop to the car) to detect what is causing this. The spark plugs usually require special tools to remove and check, which may not be possible for the average motorist. Call for professional help.
For diesel engines : Air in the fuel line. More about fuel systems later.
For both, petrol and diesel engines : The engine isn't getting enough fuel.
The engine starts, but refuses to rev up or dies out after a few seconds:
Check if there is fuel in the tank? Is there coolant in the radiator and is the engine temperature normal? Fuel flowing from tank to pipe into the engine?
Electricals: Open up the fuse box. Take out the relevant relays / fuses for fuel injection and other vitals. Ensure that they aren't blown, clean contacts and reinstall.
The fuel feed is erratic (such as with a choked fuel filter; more info in the next posts).
WARNING: Do not continue to run down the battery by repeatedly cranking the starter motor, if the engine turns over well but will not start. You don't want a dead battery over and above other issues.