Code or symptom/

Engine Cranks But Won't Start

Cranking means the starter circuit is turning the engine - it does not prove the battery is strong. A battery, terminal, or ground connection weak enough to sag system voltage during cranking can still spin the starter at a plausible speed while starving the fuel pump, injectors and ignition, so a load test stays on the list. Beyond that, what is missing is one of four things: fuel, spark, compression, or the crankshaft/camshaft signal that tells the computer when to deliver the first two. Every no-start with a healthy crank resolves into one of those, plus the voltage question underneath them. Work cheapest-first, and gather observations before buying anything. Turn the key to ON without cranking and listen for a short hum from the fuel tank area - that is the pump priming. Look for a security or immobilizer symbol lit or flashing; a car that does not recognize its key will crank indefinitely with the injectors switched off. Note whether the engine catches for half a second and dies, which means it has spark and got some fuel, versus giving no hint of firing at all. Listen to the cranking itself. A crank that sounds unusually fast, smooth and hollow suggests the engine has lost compression, which on a belt-driven engine points at a broken timing belt. Whether that also means valve damage depends on whether the engine is an interference design, and that varies by engine. Avoid cranking repeatedly. It flattens the battery, overheats the starter, and on a fuel-delivery fault it washes the cylinders with raw fuel and creates a second problem on top of the first.

Safety

The car is already stopped, so the danger is in what people do next. Do not crank for more than about ten seconds at a stretch - starters overheat and fuel floods the cylinders. Never crank or run the engine in a closed garage. If you smell fuel, stop cranking entirely and do not use anything that could spark; a leaking fuel line or a stuck-open injector is a fire hazard, and an ignition test with fuel vapour present is an ignition source. Ignition secondary voltage is high enough to give a painful shock and cause a reflex injury against a belt or fan, so use an insulated inline tester and keep hands clear of anything that can move. Starting fluid is flammable, should never be used on a diesel with glow plugs, and can damage engines with intake sensors or a mass airflow meter in the path - it is a diagnostic shortcut with real downsides, not a repair. If the car stalled in a live traffic lane, get yourself out of the vehicle and behind a barrier before you troubleshoot anything.

Narrow it down

Each question splits the possibilities. Answer them in order — by the end you should have a much shorter list than you started with.

  1. Does the engine crank at normal speed and rhythm - the same as it always has?

    If yes
    Normal cranking speed makes a badly discharged battery unlikely, but it does not clear the battery, terminals and grounds outright - voltage can still sag under load while the starter sounds fine. Move on to fuel, spark, compression and the crank signal, and measure battery voltage while cranking if those checks come up empty.
    If no
    Slow, labored, or clicking-then-turning cranking means a voltage problem, and low voltage alone can prevent starting even when the engine turns. Load-test the battery, clean both terminals and the engine-to-body ground strap, and retest before chasing anything else. Battery $150 to $350; a cleaned or replaced ground strap can be almost free.

  2. Does it catch and fire for a fraction of a second before dying?

    If yes
    It has spark, and it got some fuel. That points at fuel pressure bleeding off, an immobilizer cutting fuel just after start, a large vacuum leak, or a throttle/idle control that cannot hold it. This is actually good news - it narrows things sharply.
    If no
    Nothing is igniting at all. Something fundamental is absent: no fuel, no spark, no compression, or no crank position signal for the computer to time either one.

  3. With the key ON and the engine not cranking, do you hear a short hum from the fuel tank area?

    If yes
    The pump is at least being commanded and is spinning. That does not prove it is producing pressure - a worn pump can hum and still make no useful pressure - but it moves the relay, fuse and wiring down the list.
    If no
    Silence points at the fuel pump, its relay, its fuse, the pump driver module, or on some vehicles an inertia/crash cutoff switch. Confirm by connecting a fuel pressure gauge at the manufacturer's test port with the system depressurized first; the correct pressure figure is vehicle-specific. Pump replacement typically $500 to $1,200.

  4. Is a security, key, or immobilizer symbol lit or flashing on the dash?

    If yes
    The vehicle may be disabling fuel or spark deliberately. Try the spare key. A worn transponder, a dead key-fob battery on push-button systems, or a failed antenna ring around the ignition all cause this. Key or immobilizer repair commonly $150 to $600.
    If no
    Immobilizer is less likely, but not eliminated - some systems display nothing when they refuse to authorize. A scan tool can read whether the immobilizer has granted permission to start.

  5. Did it fail to start after sitting, rather than dying while you were driving?

    If yes
    Think fuel pressure bleeding down overnight, a marginal battery or ground, moisture in a connector, or a relay that fails when cold. Damage is less likely and the fault is often electrical or fuel-pressure related.
    If no
    An engine that quit while driving and will not restart points at a crankshaft or camshaft position sensor, a snapped timing belt or jumped chain, a fuel pump that gave out, or an ignition switch or main relay. A hot engine that cranks and will not restart until it cools for twenty minutes is a textbook crankshaft position sensor pattern - and that same fault cuts the engine out at speed without warning, so treat a car that has been stalling in traffic as not safe to drive until it is fixed.

  6. Does the cranking sound unusually fast, even, and hollow - noticeably different from how it normally sounds?

    If yes
    Suspect a loss of compression across the whole engine, which usually means a broken timing belt or a chain that has jumped. Confirm by removing the oil filler cap or a valve cover and watching whether the camshaft turns while someone cranks - keep your hands, sleeves and tools out of the opening while the engine is turning, and agree a stop signal with the person at the key first. This is the one branch where further cranking can do additional harm.
    If no
    Compression is likely present and the engine is mechanically turning as it should. Concentrate on fuel, spark and the crank/cam signal.
Likely causes and how to check each one
  1. 1

    Weak battery, corroded terminals, or a bad ground

    Very common

    An engine can crank at a plausible-sounding speed while system voltage sags too low for the fuel pump, injectors and ignition to work properly. Corrosion inside a battery terminal or a degraded engine ground strap does the same thing without looking dramatic.

    How to check

    Load-test the battery rather than just reading its resting voltage, and measure voltage at the battery while cranking. Clean both posts and inspect the ground straps between engine, chassis and body. Battery $150 to $350; terminal or ground repair often under $150.

  2. 2

    No fuel reaching the cylinders - empty tank, failed pump, relay or fuse

    Very common

    Fuel gauges and level senders do fail, and a car reading a quarter tank can be genuinely empty. Beyond that, the pump itself, its relay, its fuse, or its driver module all stop delivery completely.

    How to check

    Add a couple of gallons of known fuel as a cheap first test. Listen for pump prime at key-on, then measure actual fuel pressure at the manufacturer's test port - depressurize the system before connecting the gauge, keep the gauge and hose clear of hot and moving parts, and never tee a gauge into a live fuel line to drive the vehicle. The correct value is vehicle-specific. Relay or fuse repair is often under $100; pump replacement commonly $500 to $1,200.

  3. 3

    Crankshaft position sensor failure

    Common

    Without a crank signal the computer does not know piston position and will not fire injectors or coils, so the engine cranks perfectly and never catches. These sensors classically fail when hot and recover when cool, producing a car that will not restart after a drive but starts fine the next morning. The same intermittent failure is a stalling-at-speed fault: it can cut the engine dead in traffic, taking power steering assist and, once vacuum reserve is used up, brake assist with it. A car with this history should not be driven while you diagnose it.

    How to check

    Scan for a crankshaft position sensor code and, better, watch whether engine RPM registers on the scan tool while cranking. No RPM reading while cranking is strong evidence; back it up by checking the sensor's power, ground and signal before replacing it. Replacement typically $200 to $600 depending on access.

  4. 4

    Immobilizer or key transponder not authorizing the start

    Common

    The vehicle recognizes the key electronically before it allows fuel or spark. A failed transponder, a damaged antenna ring, a dead fob battery on push-to-start systems, or a module that has lost its key programming all leave you cranking with nothing happening.

    How to check

    Try the spare key. Watch the security light behaviour at key-on - a flashing or steady security symbol during cranking is the tell. A scan tool can read the immobilizer's status directly. Key programming or antenna repair commonly $150 to $600.

  5. 5

    Flooded engine or contaminated fuel

    Common

    Repeated crank attempts on a fuel or spark fault soak the plugs and make starting impossible even after the original fault is fixed. Separately, water or the wrong fuel in the tank prevents combustion outright.

    How to check

    Pull a spark plug - wet, fuel-smelling plugs confirm flooding. Keep the removed plug and its lead away from the plug hole, since fuel vapour is escaping there. Many engines have a clear-flood mode entered by holding the throttle fully open while cranking, but whether that applies varies by vehicle. Draw a fuel sample into a clear container, away from ignition sources, and look for water separating out. Tank drain and refill $150 to $500.

  6. 6

    No spark - ignition module, coils, or ignition switch power supply

    Occasional

    Spark can be missing because of a failed ignition module, a bad main relay, a worn ignition switch that loses the run circuit while cranking, or a wiring fault. Distributor-equipped engines add rotor, cap and distributor shaft failures.

    How to check

    Test for spark with a proper inline spark tester with an insulated boot - never hold a plug wire or dangle a loose plug near the head. Secondary ignition voltage can shock you hard enough to cause a reflex injury, so keep the tester and your hands away from belts and fans, and have someone else work the key. Do not do this with fuel pooled or a strong fuel smell present. On coil-on-plug engines, disable the injector for that cylinder or keep crank attempts to a couple of seconds so you are not filling the bore with fuel while you test. Then confirm power and ground reach the coils before condemning them, and verify the ignition switch supplies the run circuit during crank, which is a common failure point. Repairs range from about $150 to $700.

  7. 7

    Broken timing belt or jumped timing chain

    Occasional

    With no valve timing there is no compression and no combustion. The crank sounds fast and unusually smooth. Whether the pistons contact the valves depends on whether the engine is an interference design, which varies by engine - and if it is, damage has likely already occurred.

    How to check

    Remove the oil filler cap or a valve cover and watch for camshaft rotation while someone cranks briefly, keeping hands and tools out of the opening and clear of the front of the engine. No cam movement confirms it. Stop cranking immediately once confirmed. Timing belt replacement commonly $600 to $1,600; if valves were bent, repairs run into the thousands.

  8. 8

    Injectors not being commanded - wiring, driver, or camshaft sensor fault

    Occasional

    Some engines need a camshaft signal to identify which cylinder is on its firing stroke. Lose it, or lose injector power supply through a fuse or relay, and the engine cranks with spark but no fuel.

    How to check

    A noid light or a scope on an injector connector shows whether the computer is pulsing them while cranking. Check injector power supply fuses and relays. Sensor or wiring repair typically $200 to $700.

  9. 9

    Severely restricted exhaust or intake

    Rare

    A catalytic converter melted internally, a crushed exhaust pipe, or an air filter housing packed with rodent nesting material can restrict flow enough that the engine cannot run at all.

    How to check

    Look for obvious blockage in the air intake, and measure exhaust backpressure with a gauge threaded into the upstream oxygen sensor port on a cool exhaust - a restriction shows as backpressure that is higher than the manufacturer's limit, not lower, and it climbs with engine speed. Converter replacement commonly $900 to $2,800; a blocked intake may cost nothing to clear.

  10. 10

    Hydrolocked engine or internal mechanical failure

    Rare

    Water drawn into a cylinder, or a coolant leak filling a cylinder overnight, prevents the engine from compressing. Rarely, a broken connecting rod or seized component prevents normal rotation - though these usually change the cranking sound dramatically or stop it entirely.

    How to check

    If the engine will not turn over at all, or turns and then stops hard, stop immediately. To clear a suspected hydrolock, first disconnect the coils and pull the fuel pump relay or injector fuse so nothing sparks and no more fuel is added. Remove the spark plugs, cover the area with rags, keep your face, hands and any bystanders off to one side and well clear of the plug holes, and crank only in short bursts - whatever is expelled leaves at speed and coolant or oil can be hot enough to burn. Then have the source of the liquid found and fixed before the engine is run again; repeating a hydrolock bends connecting rods. Any confirmed internal failure needs professional assessment before further attempts.

Ordering reflects how often each cause is responsible in general, not a probability for your vehicle. Confirm by testing before replacing anything.

Codes commonly stored with this symptom
If the light is on

A stored trouble code narrows this considerably — it tells you what a module actually measured rather than what you noticed. Any basic scanner will read it. Look the code up here.