No-start and long-crank diagnosis: the fork in the first ten seconds

A no-start is two completely different problems wearing the same skin, and the split happens in the first ten seconds: does the engine turn over when you turn the key, or not? Cranking-but-not-catching is fuel, spark, or timing. Not-cranking-at-all is battery, cables, or starter. Mixing the two families is how people replace good parts — so make the fork call first, out loud, before touching anything.

Fork one: no-crank (nothing turns)

Work down this ladder — each step is cheaper and faster than the one below it:

1. 01**Battery voltage and connections.** Dash lights, interior behavior, and a voltage readout if you have one. A battery that cranked fine last week can still be the one that's dead today — parasitic drain and age work quietly. Corrosion or a loose clamp at the terminal does a fine battery impression.
2. 02**The jump test.** If a jump-start (or a good charger, given time) brings it to life, you're in battery territory. On these cars a new battery isn't plug-and-play — registration matters, and the [battery registration guide](../battery-registration-guide) explains why an unregistered swap eats the next battery too.
3. 03**The click family.** A single click with no turn is the starter solenoid engaging without the motor following — connections first, starter second. Rapid clicking is a voltage problem, full stop.
4. 04**The DME's own testimony.** If it set a code on the way down, the starter-activation path is instrumented:

The factory document defines the enablement window (battery between 9 V and 16 V, terminal 15 on) and its test path checks the start-request chain between the CAS and the DME before any parts are replaced — the request that never arrived is a wiring or module story, not a starter story.

Fork two: cranks but doesn't catch

The engine spinning means battery and starter are doing their jobs. Now it's the combustion triangle — fuel, spark, timing — and on these engines there's a preferred order of suspicion.

The prime check first (free, thirty seconds)

Turn the key to run — dash lit, engine off — and listen at the filler or the rear seat for the in-tank pump. It should run briefly and quiet down as the low side pressurizes. Then cycle off, key to run again, wait a few seconds, and crank. A car that starts noticeably easier with that ritual is telling you the line is bleeding down overnight — the classic N54 low-pressure check-valve story, and the opening chapter of the 2AAF fuel-pump plausibility↗ page.

The factory functional picture underneath that test:

The DME watches a pressure sensor between the electric pump and the high-pressure pump, continuously comparing actual against setpoint, and drives the pump through the EKPS control module to close the gap. That's why fuel problems announce themselves in data long before they become no-starts — the monitoring is built in.

Read the codes before anything else

The DME logs its own best diagnosis while you're still standing at the bumper:

• **Crankshaft sensor** — the no-start code that names itself:

The factory signature is precise: RPM registration stays at zero while the starter turns the engine. The test path is plug and wiring harness first, sensor second. Fault reaction: engine stalls or will not start, MIL on. If your tachometer shows nothing while cranking, you've watched this code happen in real time.

• **High-pressure fuel codes, cold start** — the B58-era family:

The factory test path walks plug and wiring at the rail-pressure sensor, then the sensor, then the high-pressure pump — and its last step is a reminder worth remembering: delete the low-pressure control adaptation data after fuel system work, so the DME relearns delivery against the new reality instead of the old one.

Spark and the rest

Fuel looking healthy moves suspicion to spark — plugs and coils have their own service guide↗, and post-flash no-starts are usually wear parts, not calibration (the tune-or-car tree↗ covers that fork honestly). A car that starts, then immediately sets misfire codes and dies is making for the misfire triage guide↗ with its story half-told.

When to stop DIY-ing

The prime check, the code read, and the battery ladder need nothing beyond a phone and a multimeter. Stop and hand it over when the path calls for a mechanical gauge on the low side (the factory 2AAF test itself), a compression test to split mechanical from electrical, or fuel-system opens — those are measured, documented procedures, and the measurement is cheaper than a second round of guessed parts. Confirmed weak delivery on a tuned car skips straight to the LPFP upgrade guide↗ — doing that job once is the whole point.