Cranks But Will Not Start
Engine cranks normally but will not fire, separating fuel, spark, compression, security, and engine-position signals.
A crank/no-start should be split into what is missing during cranking: fuel pressure, injector pulse, spark, compression, or a valid crank/cam signal. Avoid replacing a fuel pump, starter, or sensor until the missing input is proven.
Common Sounds or Signs
- Starter cranks at normal speed but engine will not fire
- Tachometer does not move while cranking
- Engine briefly fires with added fuel then stalls
- Fuel pump is silent or pressure drops quickly
- Security light flashes during start attempt
Quick Checks
- Scan all modules for P0335, P0340, P0230, security, immobilizer, and low-voltage codes before clearing
- Confirm cranking speed, battery voltage during crank, and RPM signal on the scan tool
- Check fuel pressure, fuel volume, injector pulse, and pump command before quoting a pump
- Check spark output and ignition power/ground during crank
- Use compression or relative-compression testing if fuel and spark are present
Inspection Priority
- Confirm the symptom, code, or inspection evidence before replacement.
- Check related systems when the failure pattern is not isolated.
Common Causes
- No crankshaft position signal or cam/crank correlation problem
- No fuel pressure from pump, relay, fuse, wiring, or control issue
- No injector pulse due to security, PCM power, sensor input, or wiring issue
- Ignition power, coil control, or spark output failure
- Low compression, jumped timing, flooded engine, or severe mechanical fault
Diagnostic Path
Pick the first inspection path.
Signal and Command Path
Prove the PCM sees engine speed and commands fuel and spark during cranking.
- Watch scan-tool RPM while cranking
- Check injector pulse and coil command
- Inspect CKP/CMP connectors and harness routing
Fuel, Spark, and Compression Path
Once command exists, find whether pressure, spark energy, or mechanical compression is missing.
- Measure fuel pressure and leak-down
- Check spark output under load
- Perform relative compression if fuel and spark are present
Next Best Step
Inspect before expanding the quote.
Test charging voltage
Measure alternator output and battery voltage under load.
Inspect serpentine belt
Check belt condition, tensioner travel, and pulley alignment.
Verify battery condition
Charge and load test before blaming the alternator or starter.
Related Inspection
Recommended Next Repair Paths
Compare repair paths before replacing parts.
Fuel Pump Replacement
Use only after fuel pressure, command, and power/ground testing confirm the pump path.
Electrical Diagnostic
Use when crank/cam signal, relay command, injector pulse, or security data is missing.
Explore Related Systems
Use when multiple systems overlap.