Ignition System Water Intrusion

Water intrusion in an ignition system can short out the electrical impulses sent to the spark plugs and cause a "crank no start" issue with the engine. There are many ways this can happen

Table of Contents

• 1. Causes
  • 1.1 Malfunctioning Spark Plug Wires
  • 1.2 Poor Spark Plug Protection

Causes

Malfunctioning Spark Plug Wires

If the insulation on a spark plug wire is broken, worn, cracked, chafed through on the engine block, than it will not be protecting the plug wire inside from shorting out on the engine block. Electricity is like water, it will seek the path of least resistance at all times, so if a spark plug wire is frayed and not touching the engine block than the engine will run fine in dry climates. If it rains or there is a dense fog or heavy morning dew than this can cause water to build up enough on the spark plug wire and short the system.

Poor Spark Plug Protection

In some "overhead camshaft" engines there are spark plug tubes where the spark plugs themselves are buried deep in the cylinder head. Spark plug wires and coil packs (for coil on plug ignition systems) are equipped with a seal to prevent water and general debris from getting inside the spark plug tubes, if one of these seals cracks and the tube fills with water this can cause a misfire from the electrical short caused by the water inside.