Diagnose and fix a car wont start condition
If your turn the key and your car wont start, this is a good place to bone up on what might be wrong. Or, if you you have a “car wont start just clicks,” “car wont start when cold,” “car won’t start no noise,” “car won’t start but battery is good,” this article can also help.
Asking the right questions when your car won’t start
Every day I see questions posted on auto forums with the question; “My car wont start?” Of course the poster doesn’t list the year, make, model, or engine in their vehicle. They just want to know why it won’t start. But without knowing that basic vehicle information, it’s almost impossible to answer the question. Every vehicle is different. And the reason why one vehicle won’t start may be completely different than the reason for another vehicle.
Plus, “won’t start” isn’t at all helpful. Do you mean the starter won’t crank the engine when you turn the key? Or do you mean the engine cranks, but won’t fire up? Or perhaps it fires up and dies right away—because that could also mean that the “car won’t start.” The point here is that you must be specific if you want help. Here are the terms and what they mean.
Car won’t start and no sound when you turn the key
You turn the key and hear nothing, not even a click. This can be caused by dirty battery cables, a bad ignition switch, a bad starter relay, a bad starter solenoid, or a bad starter motor.
Car clicks once or clicks rapidly but won’t crank
At least this tells us the ignition switch is sending power to the starter relay and starter motor. If you hear a single click, turn on the dome light and try again. If the dome light dims to almost nothing, that can be a sign of a dead battery or a shorted starter motor.
If you’re stuck away from home, continue to turn the key for about 6 or 7 more times. Then let it sit for about 5 minutes. If the problem is the battery, the continued key turning may heat the battery up enough to get you enough power to turn the starter motor.
BUT, if you detect a burning smell, stop immediately. That means you’re cooking the starter motor. (Not that you care that much, you’re going to have to replace it anyway, but it could ignite the insulation on the motor windings). Click here to see how to check the battery.
A rapid clicking, sounding almost like a machine gun, is a sign of a weak battery. The battery is providing just enough power to pull the starter drive towards the teeth in the flywheel, but not enough power to hold it in place and turn the starter.
For other tips on “won’t crank” click here
Starter makes a high pitch spinning sound—like WHIRRRR
That’s the sign of a failed starter motor drive gear. Try to start the engine 5 or 6 more times to heat up the grease inside the starter motor drive. That may buy you one more start. But that trick won’t carry you very far, so drive it right to the shop and have them replace the starter motor.
Car cranks but won’t fire up
If the engine cranks as fast as it normally does but won’t fire up, that can be a sign of a bad crankshaft position sensor, bad fuel pump, or a problem with your anti-theft system.
If you own a Ford vehicle, turn the key to the RUN position and wait for the Check Engine light to come on. Then crank the engine. The light should go out while cranking. If it does, that means the computer is getting a good signal from the crankshaft position sensor. If the light stays lit, start your diagnosis with that sensor.
Next, check the inertia fuel cutoff switch. This is fairly exclusive to Ford products. It’s designed to turn off power to the fuel pump if the vehicle is ever involved in a crash. But the sensor can also activate if someone bumps your car in a parking lot. It’s in a different place for each Ford model. So get out your owner’s manual. Find the location and press the reset button.
Next, try starting the vehicle by holding the gas pedal down part-way. If that helps at all, chances are you have a failing engine coolant temperature sensor. Those sensors can fail partially—not enough to set a check engine light, but enough to throw off the computer. The failed sensor makes the computer think the engine is warmer than it really is. So it provides a very lean mixture to a cold engine. By pressing the gas pedal, you override the computer’s commands and force it to provide more gas. If that works, test or replace the sensor.
If the engine isn’t getting fuel, you’ll have to perform a fuel pressure and fuel volume test and that requires special tools. Not a job for a DIYer.
Car starts and dies
This can be can be caused by a dirty or failed idle air control valve or a vacuum leak. The idle air control valve regulates how much air comes into the engine when you’re at idle. If it’s not working properly or the passages are dirty, the engine will either have too much air or will be starved for air. A vacuum leak can also cause an engine to die after starting because the leak dilutes the rich mixture the computer is providing.
© 2012 Rick MuscoplatPosted on by Rick Muscoplat
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