Diagnose car won’t start caused by starter issues
If your car won’t start and you were linked here by another post, here’s how to diagnose car won’t start caused by starter issues. The symptom: you turn the key to start and hear nothing, a single click or rapid clicking noise.
What to do when you turn the key to start and hear nothing
• Dead battery
• Corroded battery terminals
• Blown fuse
• Faulty ignition switch
• Bad park/neutral switch
• Problem with anti-theft system
• Bad starter relay
Always start your diagnosis with a battery check. Here’s how to do that.
Start by eliminating the possibility of a dead battery.
Dash lights mean nothing
If your dash lights come on steady, that is NOT an indication of a fully charged battery. Dash lights take very little power and a nearly dead battery can easily provide enough power for dash lights but not enough to power your starter.
If your dash lights blink on and off, that’s almost always a sign of a dead battery. The gauges and warning lights on late model cars are run by the computer and computers malfunction when voltage drops below 9.6-volts. So crazy warning lights or intermittent behavior is an indication of low power.
How to check battery voltage
Set a voltmeter to DC volts and connect the leads to the positive and negative battery posts. You can buy an inexpensive digital voltmeter at any auto parts store, hardware store or home center These are the voltage reading for a maintenance free battery at various charge levels and temperatures.
What the voltage reading mean when the car battery is at 50°F
12.77 volts—Fully charged, 12.37 volts—50% charged, 11.97—volts 25% charged, 11.77 volts—0% charged
What the voltage reading mean when the car battery is at 20°F
12.66 volts—Fully charged, 12.26 volts—50% charged, 11.86 volts—25% charged, 11.66 volts—0% charged
What the voltage reading mean when the car battery is at 0°F
12.56 volts—Fully charged, 12.15 volts—50% charged, 12.032 volts—25% charged, 11.80 volts—0% charged
How to test your car battery without a volt meter
Use the dome light to check car battery condition
Turn off all electrical accessories—heated seats, blower motor and rear window defogger.
Turn on the dome light (KEY in the OFF position). Is it brightly lit? If so, that’s a good sign. If it’s dimly lit, you’ve got a severely discharged battery or very corroded battery terminals. A dome light uses a very small amount of current. If the battery can’t light the dome light brightly with all other electrical accessories off, then the battery is so discharged it can’t engage the starter.
What to do? Getting a jump may help you start the engine, but you’d better plan on driving directly to a shop to get your battery tested/replace. Don’t kid yourself into thinking you’re out of the woods or can simply recharge the battery by driving. Read this post on charging a battery after a jump start to understand why this won’t work.
If the dome light burns brightly but you still hear nothing when turning the key to start, move the shifter to the neutral position and try starting. If that works, your park/neutral switch may be the culprit or the shift cable may be out of adjustment. Get it to a shop sooner rather than later because this trick won’t work forever.
Check for corroded battery terminals
Some battery corrosion is obvious, while other corrosion is invisible. The best way to check for battery corrosion is to simply clean the battery posts and terminals. That eliminates corrosion as a possibility.
Don’t have the battery cleaning tools with you? Here’s a trick, take off a shoe and tap the battery terminals a bit so they’ll rotate around the post. Don’t hit hard, just a slight tap. Sometimes that’s all it takes to reestablish connection.
Is it a blown fuse?
Attempting to jump start a vehicle can sometimes cause a fuse or fusible link to fail. If you’ve recently tried jump starting the vehicle, check all the fuses, especially those that power the ECM.
Is it a faulty ignition switch?
An ignition switch has many electrical contacts inside and they can wear out and cause intermittent connections. Just because your dash lights come on doesn’t mean the IGN switch contacts for the starter are good.
Try repeatedly moving the key from the ACCESSORY position to the START position to see if that works.
Is it a bad park/neutral switch?
Your engine won’t start if your transmission is in gear. If you have an automatic transmission, try moving the shifter to the NEUTRAL position and try starting. If it doesn’t start, move it back to PARK and try again. Repeat several times. If it finally starts, suspect a bad or intermittent park/neutral switch.
The interlock on a manual transmission is usually a switch near the clutch pedal. These engines won’t start unless the clutch if fully depressed. So try releasing and applying the clutch pedal multiple times to see if it starts.
Is the anti-theft system preventing the start?
Some anti-theft system failures prevent cranking, while others allow cranking but shut off the fuel, while still others allow the engine to start and then shut it down immediately. In all cases, an anti-theft system fault will cause the SECURITY (or similar) warning icon or light to come on. If you have an anti-theft system warning light on, follow this procedure:
• Remove the vehicle key from its keying and stow the rest of your keys away from the lock cylinder.
• Disconnect any phone chargers, Bluetooth adapter or dash cam—anything that can cause interference.
• Try starting the engine. If that doesn’t work, try your spare IGN key.
If none of those tricks work and the warning light is still on, you’ll have to call a tow truck
Is it a bad starter relay?
Most late model vehicles use a small relay in the under hood fuse box to switch power to the starter solenoid/relay. Here’s how it works; You put the key in the IGN. The anti-theft system reads the key data and sends it to the body control module (BCM). The BCM confirms the key is correct and sends a digital message to the ECM to confirm. If everything works as planned, the ECM grounds the control coil portion of the starter relay.
You can see in the starter wiring diagram below that power flows from a fuse to the control coil of the starter relay. When the ECM/PCM provides ground to the starter relay, the contacts move and power then flows through the park/neutral switch and then to the starter. In other variations, the park/neutral switches are inputs to the ECM/PCM and the computer won’t allow the starter relay to ground unless it sees a good indication from the park/neutral switches.
To rule out a bad starter relay in the underhood fuse box, locate a different relay with the same size, shape and number and swap the relays. If the engine starts, that confirms the original relay was bad.
©, 2018 Rick Muscoplat
Posted on by Rick Muscoplat