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
  • 1.3 Coil Pack Water Intrusion
  • 1.4 Poor Insulation for Cap and Rotor
  • 1.5 Ignition Control Module Damage

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.

Coil Pack Water Intrusion

Ignition coil packs are what send the high voltage electrical pulses to through the spark plug wires and to the spark plugs to ignite the fuel for combustion. A single wire or electrical connector governs the electricity sent to and from the coil pack, an insulation exposure can cause total ignition failure if there is water intrusion.

Another cause for an ignition short in an ignition coil pack is if the pack has a slight crack in the electromagnetic coil insulation itself, although this will typically cause ignition failure in any climate, if the crack is small enough or the sealed unit damaged even slightly but not enough to cause severe ignition failure than water intrusion can and will short the coil pack to the nearest ground.

Poor Insulation for Cap and Rotor

On ignition systems that use spark plug wires there is a plastic cap that protects a spinning rotor that sends the voltage to the correct spark plug wire based on engine operating conditions. The cap is meant to protect the rotor from the elements and also to pick up the pulses sent to the wires. There is a rubber seal around the edge of the rotor that aids in protecting the rotors' signals. A crack in the cap, or the seal can cause moisture or condensation to build up inside, this is why sometimes a foggy day or heavy morning dew can cause some engines with this ignition system to misfire.

Ignition Control Module Damage

Some vehicles are equipped with a small computer processor to aid in ignition timing. On most modern vehicles this computer is inside the cabin of the car, but on earlier computer controlled systems the ignition control module was located under the hood and unprotected from the elements. If any water or moisture gets inside the electrical connector or the module itself than it can also cause ignition failure.