5 Reasons Your Car Won’t Start But the Lights Come On
Few car problems are more frustrating than turning a key or pressing a start button only to be greeted with silence while your dashboard mockingly lights up. This common situation happens without warning, leaving even experienced car owners wondering what went wrong.
Read on to learn the potential causes of this issue, what it’ll cost to fix, and how to properly diagnose it to find the actual culprit.
How Your Car’s Starting System Works
To better understand what is causing your vehicle not to start, though all lights illuminate as anticipated, you must first understand the basics pertaining to ignition system operation. The ignition system is ultimately responsible for initiating engine start-up when you turn the key or push the start button.
From Battery to Ignition
As most would assume, the ignition system itself begins at a vehicle’s ignition switch. This switch directs the flow of power to critical systems via closing contacts when a vehicle’s key is turned or start button pressed. The power that is distributed originates at a vehicle’s battery, before feeding the ignition switch, and all downstream components.
From the ignition switch, power is directed to your vehicle’s power distribution panel, all intelligent modules, starter solenoid, alternator, and other components. Many older vehicles also require power to be distributed to a stand-alone ignition coil and distributor. However, most modern vehicles now create spark from a separate driver module.
Engine Start Sequence
A vehicle’s engine begins rotation when engaged by the starter motor. A positive signal to begin this rotation originates at the outlet side of the ignition switch before being directed to a secondary “switch” referred to as the starter solenoid.
Once power is applied to the starter solenoid on the correct terminal, an internal contact is closed, allowing battery voltage to be applied to the starter motor, which then turns the engine.
As an engine begins to rotate, power is further distributed to produce properly timed spark, and ample fuel for combustion. Feedback from various sensors is analyzed by the vehicle’s computer (ECM/PCM) to assess combustion efficiency. If everything works as anticipated, an engine fires quickly, settling into a steady idle within moments.
Causes of a Car That Won’t Start Yet Its Lights Turn On
There are several potential reasons for a vehicle not starting, despite the operation of all lights. Luckily, each of these underlying causes tends to be relatively simple to identify with some basic knowledge and the right tools.
#1 – Faulty or Failing Battery
A battery’s health, or a lack thereof, commonly determines how well a vehicle will start (if it will start at all). It’s not uncommon for a battery to hold enough of a surface charge to operate a vehicle’s lights, yet fall flat when attempting to start the same vehicle.
Even a battery that looks fine on the surface might have internal cell damage or sulfation buildup that prevents it from delivering the strong burst of power needed to turn over your engine.
The battery might maintain enough surface charge to light up your dash and headlights, creating the false impression that it’s working properly, while being completely inadequate for the more demanding task of starting the engine.
Cost to Fix
The cost of replacing a vehicle’s battery often depends upon the make and model of the vehicle itself. This being said, most can expect to pay between $100-$200 to have their vehicle’s battery replaced.
#2 – Bad Starter
Another common culprit behind this “no start” condition is a faulty starter motor or starter solenoid. Under such circumstances, power is being delivered as anticipated to a vehicle’s starter/starter solenoid, yet the starter itself is not engaging the engine’s flywheel or flexplate.
Your starter motor is the workhorse that physically turns your engine until it can run on its own. When this component fails, you might hear nothing at all when turning the key or pushing the start button, or perhaps just a single click.
Either the motor itself can fail electrically, or the mechanical components (e.g., pinion gear or solenoid) can become damaged or jammed. When this happens, power reaches the starter system but fails to translate into the mechanical motion needed to turn your engine.
Cost to Fix
Though starters can often be rebuilt, most now opt for the purchase of a new or remanufactured starter. On average, you can expect to pay $600-$900 to have your vehicle’s starter replaced, accounting for both parts and labor.
#3 – Poor Electrical Connections
A number of no-crank complaints annually are also tied back to poor electrical connections within the starting circuit. Corroded or loose battery/starter cables are among the most likely issues of this type and are often tied to intermittent starting Issues.
Corroded battery terminals create resistance that reduces power flow (similar to a partially blocked pipe restricting water flow). These connections might still allow enough electricity through for low-power functions like lights, but fail under the high-demand situation of starting.
Similarly, damaged cables or loose connections anywhere in the starting circuit can create intermittent problems where your vehicle starts sometimes but not others, making diagnosis particularly frustrating.
Cost to Fix
The cost of addressing poor electrical connections within a vehicle’s starting system can be highly variable, depending primarily upon whether or not replacement of any such cables will be required. Nonetheless, issues of this sort can typically be resolved for $10-$100.
#4 – Blown Fuse or Stuck Relays
It is also important not to overlook the small things when attempting to diagnose a no-crank issue. It’s not uncommon for a blown fuse or stuck relay within the starting circuit to be the source of your problem.
Modern cars and trucks protect their electrical systems with numerous fuses and relays. A fuse is designed to “blow” when too much current flows through it, preventing damage to more expensive components. Relays are electronic switches that allow a small control circuit to activate a much higher-powered circuit, like the one that powers your starter.
When a starting circuit fuse blows or a relay fails, it creates a break in the electrical path needed to start your car. The frustrating part is that these small, inexpensive components can completely disable your vehicle while leaving all other electrical systems (like lights, radio, and other accessories) functioning normally.
Cost to Fix
Luckily, replacing faulty fuses and/or relays tends to be a relatively inexpensive matter. Such items can be sourced at virtually any auto parts store, and are often available for around $10-$20.
#5 – Anti-Theft Lockout
Many of today’s newer vehicles come equipped with a variety of anti-theft technology. These systems use transponder chips embedded in your key or key fob that communicate with your vehicle’s computer. This technology typically makes it impossible for a vehicle to be started, if an electronic ID chip within the key is not recognized at start-up.
This can happen due to a damaged chip in your key fob, a faulty receiver in the vehicle’s ignition system, or even a computer glitch in the vehicle’s security module. If your vehicle’s lights prove functional, yet your vehicle’s engine won’t crank, it is entirely possible that you have encountered an anti-theft lockout.
Cost to Fix
Anti-theft lockout issues vary in cost to fix. Most often, the problem is a faulty key chip or the key decoder inside your vehicle. Fixing these issues typically costs between $200-$500 to get you back on the road.
Diagnostic Process (Step-by-Step)
The following steps can be used to assist you in diagnosing your vehicle’s no-crank issues. It is also advisable to have a model-specific wiring diagram on hand to assist with this troubleshooting.
#1 – Inspect Battery/Starter Cables
Begin by carefully inspecting your vehicle’s battery and starter cables for signs of damage or corrosion. You should also verify that the connections are tight and secure at each end of these cables.
#2 – Test Battery Voltage
Next, with the use of a multimeter, check the voltage between the positive and negative posts of your vehicle’s battery. Ideally, a reading of approximately 12.6V should be registered. Significantly lower readings would necessitate battery replacement.
#3 – Load Test Battery
If sufficient battery voltage was registered in the previous step, perform a load test. Do this by repeating the voltage test above while having an assistant attempt to start the vehicle. Battery voltage should not drop below 9.6V under such testing.
#4 – Verify Power Delivery to Starter
Now you’ll need to verify power delivery to the vehicle’s starter motor. Using a quality multimeter, ground the meter to the body of the starter, while probing the primary terminal on the starter body with the meter’s positive lead.
Have an assistant attempt to crank the engine while gaining voltage as described above. If you see approximately 12V, yet the starter itself does not engage, you’ll need to replace the starter.
#5 – Verify Solenoid Operation
If no power was present on the starter motor’s primary terminal during step #4, you will need to test the starter’s solenoid.
First, test to ensure that nominal battery voltage is present at the solenoid’s main cable terminal while the vehicle is sitting idle. If power is present at this point, yet not at the outlet side of the solenoid when attempting to turn the ignition, the trigger feed to the solenoid should be tested.
Use your meter to check if power appears at the smaller solenoid terminal when attempting to start. If voltage is present here but the solenoid doesn’t activate, the solenoid itself has failed.
#6 – Check Ignition Circuit
If no trigger voltage was recorded at the point specified above during attempted cranking, further diagnosis of the ignition circuit will be required. This is best accomplished by tracing a wiring diagram for your particular model of vehicle while following the manufacturer’s recommendations.
The exact routing of this circuit differs by vehicle, yet typically feeds through a vehicle’s neutral safety switch, starting relay, and starting fuse, before tying back to the outlet side of the ignition switch itself.
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