When your starter spins the engine but it never catches, the engine is missing one of four basics: spark, fuel, compression, or the right signal from the computer. The good news: you can narrow it down in about 5 minutes with no tools.
The most common no-fire cause. The crankshaft position sensor tells the ECM when to fire the coils. No signal = no spark. Codes P0335 or P0340 confirm it. Pull a plug and check for spark while someone cranks.
Get a full diagnosis →Turn key to ON and listen for the 2-second fuel pump hum from the rear. No hum = pump, fuse, relay, or wiring. Hum but won't start = could be a clogged filter or failed pressure regulator.
Get a full diagnosis →Even if you have spark and fuel, the engine needs to know piston position to fire the right cylinder at the right time. A failed cam or crank sensor can let it crank perfectly but never fire. Check P0335 and P0340.
Get a full diagnosis →If you recently heard a snap or clatter and it died, the timing belt may have broken. The engine will spin freely but with no compression. On interference engines this can also bend valves. Compression test confirms.
Get a full diagnosis →Less common but real. If sensors check out and you have spark and fuel but it still won't fire, the engine computer itself may not be commanding ignition. Code P0606 points here.
Get a full diagnosis →Tell us your symptoms and any codes. In under 60 seconds you'll get a step-by-step diagnosis tailored to your car, the parts you need, and what a fair repair should cost.
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If your scanner is showing one of these, that's your starting point. Tap any code for full causes and repair costs.
Spark, fuel, compression, and the correct timing signal from the crank/cam sensors. If your engine cranks but won't fire, one of these four is missing. Diagnose in that order - spark and fuel are by far the most common.
Classic signs: car cranks fine but never fires, no tach movement during crank, often pending code P0335. The dead giveaway is when the car starts cold but won't restart hot - heat-failing crank sensors are a common Hall-effect failure.
On many cars, yes - if the immobilizer doesn't recognize the key, the ECM won't fire injectors or coils even though the starter still works. Try the spare key. A "key" or "security" light flashing on the dash is the giveaway.
Typically $120-180 just to look at it, on top of any repair. Our $5.99 AI report walks you through the same diagnostic logic and tells you the most likely fix before you spend anything.
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