Crank-no-start triage
A crank-no-start is only a handful of categories. The fastest wins come from proving what you do have (RPM, fuel pressure, spark, injector pulse) before you chase what you don't.
Step 0: confirm the basics
- Cranking speed: a slow crank can mimic fuel/spark issues. Check battery voltage under crank and connections.
- Immobiliser / key: security light behavior matters. If the immobiliser is active, you can lose injector pulse or spark.
- Fuel in the tank: don't assume the gauge is right (especially after battery disconnects or sender faults).
- Recent work: timing belt/chain, sensors, battery, starter, fuel system, jump-starts, water ingress.
What to capture (2 minutes)
- Codes (stored + pending) and freeze frame
- Live data while cranking: RPM, ECT, throttle, MAP, battery voltage
- Listen: does it sound like normal compression?
The 4 buckets
- Fuel: no/low pressure, no injector pulse
- Spark: no spark or weak spark
- Air/compression: no compression, timing slip, major air restriction
- Control: crank/cam signal, immobiliser, ECU power/grounds
Fast decision path (works on most cars)
- Do you have cranking RPM? If RPM stays at 0, suspect crank sensor signal, wiring, ECU power/ground, or scan tool limitations.
- Do you have fuel pressure? If unknown, measure. If low: pump supply, filter, regulator, in-tank module, relay, wiring drop.
- Do you have spark? Use a proper spark tester if possible. No spark can be crank signal, ignition feed, coil control, immobiliser.
- Do you have injector pulse? No pulse with RPM present points toward immobiliser, ECU control, or missing sync (cam/crank correlation).
- Compression / timing sanity: if it spins "too fast" or sounds uneven, test compression and consider timing slip.
Common patterns that save time
- Cranks but RPM=0: crank sensor circuit, connector damage, sensor gap, wiring, ECU power/ground.
- Fuel pressure OK, spark OK, still no start: flooding, incorrect timing, no injector pulse, immobiliser, air restriction.
- Starts with spray then dies: fuel delivery issue (pressure/volume), injector power feed, immobiliser cut.
- Just after engine work: missed ground strap, connector swapped, cam/crank timing alignment off.
Pro move: If you suspect wiring, do a quick voltage drop test on power and grounds during cranking. A good battery doesn't help if the starter/ECU isn't receiving it.