Quick Check – Ignition System

Cranks, No Start – Ignition Quick Check (Universal)

Driveway checks to prove spark, power, trigger, and timing reference fast. This page routes decisions. Tests live in the QC library and QTS guides.

Symptom: Cranks, No Start

Starter spins the engine normally, but the engine does not attempt to fire. This sequence isolates ignition by proving spark, power, trigger, and timing reference in a fixed order.

Step 1: Prove Spark Presence

Install an inline spark tester at one cylinder (or use a known-good plug grounded to clean metal). Crank the engine and observe the tester.

• If spark is present: go to Step 4 (timing/reference checks).
• If spark is not present: go to Step 2 (power during crank).

Proof: If you need a defined spark test method, run: QC 1 – Spark Presence Test.

Step 2: Verify Ignition Power During CRANK

This is the primary proof gate. Confirm the coil/module has power while the starter is engaged (CRANK), not just key ON.

• If voltage is present in CRANK: go to Step 3.
• If voltage is missing or collapses in CRANK: fault confirmed. Repair power feed before continuing.

Proof: Run: QC 2 – Run/Crank Voltage Check.

Step 3: Prove Trigger Signal (Crank/Distributor)

If power is present but there is no spark, the next question is whether the ignition is being commanded to fire. Prove the trigger signal before replacing ignition parts.

• If trigger signal is valid: go to Step 4.
• If trigger signal is missing/invalid: fault confirmed. Repair sensor/trigger circuit before continuing.

Proof: Run: QC 3 – Trigger Signal Proof.

Step 4: Verify Timing Reference (Spark Happens at the Right Time)

Spark can be present and still be wrong. Verify distributor indexing/base timing (if applicable) or crank trigger reference alignment. Severe offset can produce a no-start.

• If timing reference is correct: go to Step 5.
• If timing reference is incorrect: fault confirmed. Correct indexing/base timing and re-test.

Proof: Run: QC 4 – Base Timing / Index Check.

Step 5: Prove Spark Energy (Not Just Spark)

If spark is present and timed correctly but the engine still will not light, confirm spark strength under compression conditions: plug gap, coil output, wire type, and system voltage during crank.

• If spark energy is sufficient: go to Step 6 (system boundary).
• If spark energy is weak/intermittent: fault confirmed. Repair coil, wiring, grounds, or voltage drop before continuing.

Proof: Run: QC 5 – Spark Energy Check.

Step 6: System Boundary Check

If all ignition proofs pass (spark present, power in CRANK, valid trigger, correct timing reference, sufficient energy), the ignition system is not the cause of the no-start.

• Return to fuel diagnostics: Cranks, No Start – Fuel Quick Check
• Or verify mechanical timing and compression.