QC – No Spark After Repair

QC – No Spark After Repair

Symptom: Engine had spark before recent work. After repair or modification, there is now no spark.

Rule: When spark disappears immediately after a repair, assume a human-introduced fault until proven otherwise.

Tools: Spark tester, multimeter, 12V test light, basic hand tools.

Safety: Key off while reconnecting components. Use insulated tools for spark checks. Keep hands clear of belts/fan.

0) Prove the no-spark condition

Do not rely on a removed plug or visual guess. Load the circuit.

  1. Install a spark tester.
  2. Crank the engine.
    Result:
    • Spark present: ignition works. Use another QC page.
    • No spark: continue.

    Proof: QTS – No Spark Confirmation Test (coming)

1) Verify all disturbed connectors and grounds

Most post-repair no-spark issues are simple connection errors.

  1. Re-seat all ignition-related connectors. Coil, module, crank/cam sensors, grounds.
  2. Check grounds disturbed during the repair. Engine, head, firewall, battery.
  3. Look for pinched wires or trapped harnesses.

    4. Proof: QTS – Connector / Ground Recheck After Repair (coming)

2) Ignition feed and fuse sanity check

Blown fuses and missed feeds are common after component replacement.

  1. Check ignition-related fuses and relays.
  2. Verify voltage at coil/module feed.
    Result:
    • No voltage: repair fuse, relay, or feed.
    • Voltage present: continue.

    Proof: QTS – Ignition Feed After Repair Test (coming)

3) Trigger signal reconnection

Crank and cam sensor connectors are easily misaligned or damaged during repairs.

  1. Confirm correct sensor connectors. No swapped or misrouted plugs.
  2. Inspect pins. Look for bent, pushed-back, or damaged terminals.
  3. Verify sensor air gap if adjustable.

    4. Proof: QTS – Crank/Cam Reconnection Sanity Check (coming)

4) Timing reference integrity

Any work involving distributors, timing components, or engine position can eliminate spark if indexed incorrectly.

  1. Distributor systems: Verify rotor indexing and distributor seating.
  2. Crank trigger systems: Verify trigger wheel orientation and sensor alignment.

    3. Proof: QTS – Timing Reference After Repair Check (coming)

5) Component compatibility check

Incorrect or incompatible replacement parts can eliminate spark entirely.

  1. Verify part numbers. Coil, module, sensor must match system requirements.
  2. Check polarity and wiring changes. Especially on aftermarket ignition components.

    3. Proof: QTS – Ignition Component Compatibility Check (coming)

6) Decision closure

  • Connector/ground issue found: correct and retest.
  • Ignition feed missing: repair fuse, relay, or wiring.
  • Trigger signal missing: repair sensor connection or damage.
  • Timing reference incorrect: re-index and retest.
  • Wrong/incompatible part: correct component selection.

Next links: Ignition Troubleshooting Hub | QC – Cranks, No Start | QC – Intermittent No Spark | QC – Starts Then Stalls