Quick Check – Ignition System

QC – Starts Then Stalls (Ignition)

Tools: Spark tester, multimeter, 12V test light, jumper lead, basic scan tool (optional).

Safety: Keep hands clear of belts/fan. Avoid fuel vapor during repeated starts. Use insulated tools when checking spark.

0) Prove whether ignition is causing the stall

You must know if spark is lost at the moment of stall. Guessing here sends you into the wrong system.

1. Install a spark tester and start the engine. Watch the tester as it stalls.
   Result:
   • Spark continues while engine dies: Ignition is not causing the stall. Exit to Fuel QC.
   • Spark drops out as it stalls: Continue.
   
   Proof: QTS – Spark Loss at Stall Test (coming)

1) RUN vs START ignition feed check

Many engines fire on the START circuit and die when the key returns to RUN due to a failed ignition switch or feed.

1. Back-probe ignition feed at coil or module.
2. Key in START: verify 12V present.
3. Key released to RUN: verify 12V remains.
   Result:
   • Voltage lost in RUN: ignition switch or RUN feed failure confirmed.
   • Voltage stable: Continue.
   
   Proof: QTS – Ignition Switch RUN Feed Test (coming)

2) Ignition enable or shutdown input

Modern and retrofit systems often have an enable input that will shut down ignition seconds after start.

1. Watch scan data or indicator lights (if equipped). Look for loss of RPM, ignition enable, or security status at stall.
2. Anti-theft / enable check: If equipped, temporarily disable or bypass per factory procedure to confirm.
   Result:
   • Engine stays running with enable bypassed: enable/anti-theft circuit confirmed.
   • No change: Continue.
   
   Proof: QTS – Ignition Enable / ASD Shutdown Test (coming)

3) Primary switching continuity during run

If ignition feed is present but spark stops, verify whether the coil is still being triggered.

1. Test coil primary control. Connect a test light to battery positive and probe coil negative or driver wire.
2. Observe during start and stall.
   Result:
   • Pulsing stops at stall: ECU/module stopped triggering. Go to Step 4.
   • Pulsing continues: coil or secondary failure. Go to Step 5.
   
   Proof: QTS – Coil Primary Dropout Test (coming)

4) Loss of trigger: sensor or controller heat/logic fault

Loss of primary switching points to crank/cam signal loss or controller logic shutting down.

1. Check RPM signal at stall.
   No RPM: crank/cam sensor or wiring fault.
2. RPM present but no trigger: ignition module or ECU driver failure.
3. Wiggle test harnesses. Lightly move sensor and module wiring during run to provoke the fault.

Proof: QTS – Crank/Cam Signal Dropout Test (coming)

5) Coil or secondary breakdown during run

If primary switching continues but spark stops, the coil or secondary path is failing once running.

1. Swap-test coil. Install known-good coil and retest.
2. Inspect secondary components. Look for heat cracks, carbon tracking, loose boots, or excessive plug gap.

Proof: QTS – Coil Run-Time Failure Confirmation (coming)

6) Decision closure

• Spark continues during stall: ignition ruled out. Route to Fuel QC.
• Spark lost when key returns to RUN: ignition switch or RUN feed fault.
• Primary switching lost: crank/cam signal or controller shutdown.
• Primary switching present, no spark: coil or secondary breakdown.

Next links: Ignition Troubleshooting Hub | QC – Cranks, No Start | QC – Hot No Start | QC – Intermittent No Spark