Car won't start

The short version

Listen first. A no-start is really four different problems wearing the same coat, and the sound tells you which one showed up:

• Rapid clicking — the battery can't hold voltage under the starter's load. Battery, connections, or charging.
• One solid clunk, then nothing — the starter engaged but didn't turn. Starter territory, usually.
• Complete silence — the start command isn't reaching the starter at all. Often the cheapest family: shifter position, the neutral-safety interlock, security, a truly flat battery.
• Cranks strong but never fires — the electrical system is fine; the engine is missing fuel, spark, or permission from the security system.

Then let the data sharpen it. Even on a car that won't start, the OBD2 port is live with the key on — and the two most diagnostic numbers of all, resting voltage and the voltage dip during cranking, are exactly the ones a no-start hands you for free.

The battery & charging test, codes, and live data are free in Fixiom — always, no credits and no subscription. On a no-start it grades what it can reach and says honestly which parts of the test it couldn't run.

What each sound means

Rapid clicking — machine-gun style

Each click is the starter relay slamming shut, the battery voltage collapsing under the starter's enormous draw, the relay releasing, voltage recovering, and the cycle repeating several times a second. The message: there isn't enough usable battery behind the attempt. That's a battery discharged or aged, terminals corroded or loose enough to choke the current, or a charging system that never refilled the battery on yesterday's drive. The voltage numbers below split those apart.

One clunk, then nothing

The solenoid threw the starter gear into place — that's the clunk — but the motor didn't spin the engine. Usually a starter at the end of its life (worn brushes, a dead spot), sometimes a connection delivering enough current to clunk but not to crank. A battery reading healthy at rest that barely dips at the attempt points harder at the starter; a battery that craters points back at power supply. (An engine seized solid produces this too — rare, and usually preceded by a very bad day's warning signs.)

Complete silence

The start command never reached the starter. Before assuming the worst, run the cheap list: shifter fully in Park (or try Neutral — a worn neutral-safety switch often answers to one and not the other), steering lock not binding the key, security light behaving normally rather than flashing a protest, brake or clutch pedal fully pressed where required, and a battery that isn't so flat the dash itself is dark. That list resolves a remarkable share of "silent" no-starts for free.

Cranks strong, never fires

The battery, starter, and connections are all doing their jobs — the engine is turning at normal speed and simply not catching. This is its own section below, because it's the one where live data earns its keep.

The battery numbers

Two readings tell most of the electrical story, and Fixiom's free battery test walks through both — or you can read them off the live voltage gauge yourself.

• Resting voltage, everything off: a healthy, charged battery sits around 12.6 volts. The mid-12.2s is roughly half charge. Below about 12.0, the battery is deeply discharged, failing, or being drained — and rapid-clicking behaviour is exactly what it produces. (Rules of thumb; cold weather reads slightly lower.)
• Voltage during cranking: the dip while the starter pulls is the closest thing to a load test you can get from the driver's seat. A healthy system typically stays above roughly 9.5–10 volts mid-crank; a battery that plunges well below that under load is waving a flag even when its resting number looked respectable.
• If it starts: charging voltage. Around 13.5–14.8 at idle is the classic healthy band — though many newer vehicles manage charging deliberately and legitimately sit outside it at times, which the test accounts for rather than crying wolf.

An honest limit, stated plainly: voltage is a triage, not a verdict. A battery can rest at 12.6 and still lack the capacity to start an engine — proving that takes a real load or conductance test, which most parts stores run for free. The voltage numbers tell you whether that trip is worth making.

One more free clue: eyes on the terminals, engine off. White or green crust, a cable you can wiggle by hand, or aftermarket add-ons clamped to the posts are all findings — corrosion chokes exactly the huge current a starter needs.

Cranks fine but won't fire

Now the question is what's missing: fuel, spark, or permission. From the driver's seat, key on:

• The security light. Steady-then-off during the attempt is normal on most vehicles; a security lamp flashing or staying lit while the engine cranks-but-won't-fire suggests the immobiliser isn't accepting the key — common after battery changes, with worn keys, or with aftermarket remote-start gear in the chain. The fix conversation is entirely different from a fuel or spark one, which is why it's checked first.
• Engine RPM during cranking. Watch the tachometer signal in live data while cranking: a reading in the low hundreds of RPM proves the computer is seeing the engine turn. A dead zero while the engine audibly spins points at the crankshaft position sensor — a sensor whose failure produces exactly this symptom, since without it most computers won't fire injectors or coils at all.
• Coolant temperature plausibility. On a cold morning, coolant and intake temperatures should both read close to the weather. A coolant sensor claiming a warm engine on a frozen morning leads the computer to under-fuel a cold start badly enough to prevent one.
• Fuel rail pressure, where the vehicle reports it. Key on: many systems prime to a specified pressure before the first crank. A reading near zero that never rises is a strong fuel-delivery lead. Not every vehicle exposes this — Fixiom shows it only if yours genuinely answers.
• Codes, including pending. A crank sensor, cam sensor, or fuel-system code stored during failed attempts frequently names the culprit outright.

Starts, then dies

A start that catches and stalls within a second or two is its own pattern, and the usual suspects are specific:

• Security again — many immobilisers permit the start and then kill fuel when the key doesn't authenticate. The security lamp's behaviour at the moment it dies is the tell.
• Idle control or a serious vacuum leak — the engine fires on the prime and can't sustain an idle. Sometimes it will stay running with a little throttle; that fact itself is diagnostic, and from there the vacuum-leak guide takes over.
• Fuel delivery fading — pressure enough to prime, not enough to run. Where rail pressure is reported, watching it sag as the engine dies is the whole story in one trace.

Two things not to do

What a phone adapter can't see

What it genuinely gives you: resting and cranking voltage — the two most diagnostic numbers in the no-start world — cranking RPM, temperature plausibility, rail pressure where reported, and any codes the failed attempts stored. That's a real triage, from the seat, for free.

What it cannot do:

• Prove battery capacity. A real load or conductance test does — most parts stores run one free, and the voltage numbers tell you whether to make the trip.
• Measure starter current draw — an amp clamp and hands.
• Check actual fuel pressure on vehicles that don't report it — a gauge on the rail.
• Test for spark. That's tools-out territory.
• Fix a no-crank in a parking lot. But it can turn "it won't start" into "healthy battery, cranks at normal speed, zero RPM signal, crank-sensor code stored" — which is a diagnosis, and a far cheaper conversation to walk into a shop with. For context, a diagnostic at an independent US shop typically runs around $131 to $209 per published RepairPal averages; arriving with the evidence is how that hour gets spent fixing instead of finding.

Common questions

Related guides

• Check engine light on — The triage page — how urgent is it, and what to do in what order.
• P0300 — Random misfire — and the per-cylinder counters that show which one it really is.
• Vacuum leak symptoms — Rough idle that smooths out at speed — and the trim pattern that proves it.