Identify the Symptom

Goal: pick the right path No guesswork

Be honest about what it is actually doing:

1. Cranks, no start (possible no spark) – go to Step 2
2. Cold no spark – go to Step 3
3. Hot no start – go to Step 5
4. Starts then stalls – go to Step 5
5. Misfire under load / high RPM – go to Step 5
6. Random misfire – go to Step 5
7. Ignition cutout while driving – go to Step 5

This hub behaves like a flow chart. Follow your condition.

Do I Have Spark?

Goal: prove spark exists Coil output first

1. Disable fuel and crank the engine.
2. Test for spark at the coil output (not the plug first).

Run the numbered Quick Tests (QT): Universal Ignition System Quick Tests (QT)

Jump straight to QT 1 (Spark Gate): QT 1 – Spark Gate

Full symptom walk-through (QC page): QC – Cranks, No Start

Decision: No spark at coil -> Step 3. Spark at coil -> Step 4.

Deep Dive Explainers:
Primary vs Secondary Ignition Circuits | Spark Energy vs Spark Voltage

No Spark at the Coil

Goal: prove power vs trigger Feed / ground / trigger

Start here (QT links):

1. QT 2 – Coil Power During Crank
2. QT 3 – Trigger Proof (Module/ICM Switching)
3. QT 4 – Pickup Proof (Distributor/Crank Signal)

Full symptom walk-throughs (QC pages):
QC – Cold No Spark | QC – Intermittent No Spark | QC – No Spark After Repair

Decision: power/ground not proven -> Step 6. power/ground proven -> trigger/module path.

Deep Dive Explainers:
Magnetic vs Hall-Effect Sensors | Crank Trigger vs Distributor Trigger

Spark Present at Coil, Not at Plugs

Goal: confirm spark delivery Distribution path

Start here (QT link):

1. QT 5 – Spark Delivery (Cap/Rotor/Wires)

Full symptom walk-through (QC page): QC – Weak Spark

Decision: Spark delivery fixed -> system OK. Still failing under load/hot -> Step 5.

Deep Dive Explainers:
Suppression vs Solid-Core Plug Wires | Resistor vs Non-Resistor Spark Plugs

Intermittent or Under-Load Failures

Goal: catch heat, RPM, and dropout issues Most common ignition failures live here

Start here (QT links):

1. QT 6 – Ignition Switch Voltage Drop
2. QT 7 – Base Timing Proof (Distributor Setup)
3. QT 8 – Mechanical Sync (Timing Chain)

Full symptom walk-throughs (QC pages):
QC – Hot No Start | QC – Starts Then Stalls | QC – Misfire Under Load | QC – High RPM Misfire | QC – Random Misfire | QC – Ignition Cutout While Driving

After-repair path (QC): QC – No Spark After Repair

Decision: voltage drop or bad grounds -> Step 6. repeat high RPM miss -> Step 7.

Deep Dive Explainers:
Coil Saturation and Heat Limits | Ignition Energy Limits at High RPM | Dwell Time (What It Is and Why It Matters)

Wiring Fixes (Power and Grounds)

Goal: kill voltage drop Ignition is power-sensitive

1. Voltage drop on ignition feed while cranking (run vs crank matters).
2. Voltage drop on module/ECU ground (not just continuity).
3. Grounds must be on clean bare metal, tight, and protected.
4. Avoid shared grounds with high-current devices.

Wiring guide (QC page): Wiring 101 – Ignition Power and Ground

Back to QT power checks: QT 2 – Coil Power During Crank | QT 6 – Ignition Switch Voltage Drop

Deep Dive Explainers:
Ignition Switch and Run/Crank Voltage Drops | Ignition System Voltage Sensitivity | Grounding in Ignition Systems

Decide If the Ignition System Has Hit Its Limit

Goal: stop repeat failures Upgrade only when proven

1. High RPM misfire persists after wiring and delivery are proven good.
2. Misfire increases with cylinder pressure (boost/nitrous/compression) despite correct plugs and gap.
3. Repeat confirmed thermal failures (module/coil) with verified voltage supply.
4. Dwell/saturation limits are proven (not guessed).

Deep Dive Explainers:
Cylinder Pressure vs Spark Requirement | When an Ignition System Is “Out of Headroom”

Safety While Testing Ignition

Goal: do not get hurt High voltage hazard

1. Use a real spark tester (no “hold the wire near ground” nonsense).
2. Keep hands, clothing, and leads clear of rotating parts.
3. Disable fuel for extended cranking and spark tests.
4. Do not hot-swap ignition modules/coils with the key on.

Safety guide: Ignition System Safety

Symptom QC Pages Index

Goal: longer walk-throughs Use when you need detail

Numbered driveway proofs live here: Universal Ignition System Quick Tests (QT)

1. QC – Cranks, No Start
2. QC – Hot No Start
3. QC – Cold No Spark
4. QC – Starts Then Stalls
5. QC – Intermittent No Spark
6. QC – Misfire Under Load
7. QC – High RPM Misfire
8. QC – Random Misfire
9. QC – Weak Spark
10. QC – Ignition Cutout While Driving
11. QC – No Spark After Repair
12. Wiring 101 – Ignition Power and Ground
13. Ignition System Safety

Next Moves

Goal: keep you moving No looping

1. Run the numbered QT page first: Universal Ignition System Quick Tests (QT)
2. If you need more detail for your exact symptom, grab the matching QC page from the index above.
3. If Step 7 triggers are proven, exit diagnostics and move to upgrade logic (system-level change, not random parts).