Quick Check – Ignition System

QC – Cold No Spark (Ignition)

Tools: Spark tester (or known-good plug), multimeter, 12V test light, jumper lead.

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

0) Confirm true no-spark (do not assume)

Cold start problems often get misdiagnosed as fuel. You must prove spark absence before staying in this lane.

1. Check spark output while cranking cold. Use a spark tester or grounded spare plug.
   Result:
   • Strong spark present: Ignition is not blocking start. Exit to Fuel QC.
   • No spark or extremely weak spark: Continue.
   
   Proof: QTS – Spark Output Test (coming)

1) Cold cranking voltage and cranking speed

Low cold voltage or excessive starter draw can prevent sensors and modules from operating correctly.

1. Measure battery voltage while cranking cold.
   Pass: about 9.6V or higher.
   Fail: voltage collapses below spec or cranking speed is obviously slow.
   If fail: repair battery, cables, grounds, or starter before continuing.
   Proof: QTS – Cold Crank Voltage Drop (coming)

2) Verify ignition power feed (cold)

Some ignition feeds fail only when cold due to cracked solder joints, relays, or high-resistance connections.

1. Key ON (RUN): Verify 12V at coil positive or ignition power feed.
2. Cranking (START): Watch the same point while cranking.
   Result:
   • No power in RUN or START: repair feed, relay, or ignition switch circuit.
   • Power stable: Continue.
   
   Proof: QTS – Ignition Feed Voltage Check (coming)

3) Is the coil being triggered?

If power is present but there is no spark, determine whether the coil primary is being switched.

1. Test coil primary control. Hook a test light to battery positive and probe the coil negative or driver wire while cranking cold.
   Result:
   • Light pulses: Primary switching is present. Go to Step 4.
   • No pulsing: No trigger. Go to Step 5.
   
   Proof: QTS – Coil Primary Switching Test (coming)

4) Primary switching present, still no spark

This points to a cold-sensitive coil or secondary path problem.

1. Swap-test the coil. Install a known-good coil and retest spark cold.
   Result:
   • Spark returns: coil confirmed faulty (cold open or internal crack).
   • No change: continue.
2. Inspect secondary components. Check plug wires, boots, coil tower, and plug gap for moisture intrusion or carbon tracking.

Proof: QTS – Coil Cold-Failure Confirmation (coming)

5) No primary switching – prove sensor signal and grounds

No trigger means the controller does not see a valid crank/cam signal or lacks proper power/ground. Cold opens are common here.

1. Check for RPM signal during crank.
   No RPM: suspect crank sensor, wiring, air gap, or sensor power/ground.
   RPM present: suspect ignition module, ECU output, or enable logic.
   Proof: QTS – Crank Sensor Signal Check (coming)
2. Cold harness flex test. While cranking, gently move the crank sensor and ignition module harnesses. If spark appears, repair the connection.
3. Ground integrity check. Verify engine and module grounds. Cold contraction can open marginal ground paths.

Proof: QTS – Ground Voltage Drop Test (coming)

6) Decision closure

• No spark + no ignition feed: repair power supply, relay, or ignition switch circuit.
• No spark + no primary switching: prove crank/cam sensor signal, module power, and grounds.
• Primary switching present, no spark: coil or secondary cold-fail confirmed.
• Spark present: exit to Fuel QC or compression/mechanical checks.

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