MerCruiser 4.3L No-Spark
My MerCruiser 4.3 L V6 engine cranks but will not start up and run. I know people say that every engine requires spark, fuel, compression/air and timing to fire and begin to run.
I am sure I have sufficient fuel supply and my mechanic did a compression test on the motor a few months back and said the results were fine. So I am guessing I have no spark?
What should I check if the ignition is not generating spark or weak spark? My motor is a MCM 4.3 Liter LX Alpha I.
Answers ( 3 )
No Spark
The factory service manual for this model engine contains a troubleshooting guide. It lists possible causes of no spark for conventional ignition systems and thunderbolt IV HEI ignition system. This is what it says…
No Spark – Conventional Ignition
• Check for moisture on the ignition components. Spark plug leads or distributor cap arcing.
• Damaged electrical wiring, loose electrical connection or dead battery.
• Faulty ignition switch. The MerCruiser engine may run in start position and loose spark in the running position.
• Faulty shift interrupter switch.
• Tachometer has shorted. Disconnect the tachometer and try to start the engine again.
• Ignition timing incorrect. This is often the case when the engine may crank over hard, try to run backwards or backfire.
• Ignition resistor wire or bypass wire faulty.
• Ignition points burned, dirty or gapped incorrectly.
• Fouled, bad spark plug, improperly gapped or cracked porcelain.
• Faulty spark plug wires. Faulty insulation, cut wires or boot not seating.
• Distributor cap or rotor is dirty or cracked.
• Bad coil.
• Condenser.
No Spark – Thunderbolt IV HEI Ignition
• Wet ignition components.
• Bad battery, loose electrical connections or damaged wiring.
• Faulty ignition switch.
• Faulty shift interrupter switch.
•Shorted tachometer (unplug the tachometer and try again).
• Ignition timing.
• Faulty, worn, damaged or improperly gapped spark plug.
• Damaged spark plug wires.
• Distributor cap is cracked or dirty.
• Ignition components malfunction. Test components.
• Engine synchronizer (if equipped) connected in series on purple ignition wire (only applies to dual engine). It should be connected directly at coil terminal, or parallel circuit.
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How would one go about troubleshooting the Thunderbolt IV ignition?
Troubleshooting guide.