Causes When Spark Plugs are Wet with Gasoline

By | January 29, 2023

Causes When Spark Plugs are Wet with Gasoline
Spark plugs that are wet with gasoline, are caused by the inadequate spark to the air/gas mixture, or too much gas leaking into the cylinder.

Sometimes called flooding the engine, the fix can be a bad injector or a component of the spark such as wires and coil.

An engine will misfire with wet spark plugs and may not start.

3 Causes When Spark Plugs are Wet with Gasoline

  1. No Spark
  2. No Spark
    If there is no spark, fuel will go into the cylinder but not ignite, causing an issue.

    This will cause the spark plug to get wet with fuel and foul out.

    The cylinder that is having the issue can be tested to see if there is a spark.

    When multiple cylinders have wet spark plugs, the entire spark system can be tested to be sure there is fire going to all the cylinders.

  3. Bad Fuel Injector
  4. Bad Fuel Injector
    A faulty fuel injector can leak fuel which will soak the spark plug in fuel.

    Often called flooding the engine, when too much fuel is in a cylinder, the spark plug will have a hard time igniting.

    There is also usually low fuel pressure since the injector is leaking, and no pressure can be built up.

    If only one cylinder has a wet spark plug, the fuel injector can tested or be swapped with a good cylinder to see if the issue follows.

  5. Blown Head Gasket
  6. Blown Head Gasket
    A blown head gasket can leak fluid into the cylinders causing wet spark plugs.

    Usually, the fluid will be coolant, but if the plugs foul out from the coolant, gas will not burn away and will flood the cylinder.

    If the spark plug has both gas and coolant, the engine likely has a bad head gasket.

What Causes Spark Plugs to Get Wet with Gas?

The three main causes of spark plugs wet with gas include a leaky fuel injector, no spark, and a blown head gasket.

A leaky fuel injector will flood the cylinder with gas which will soak the plugs.

If there is no spark, then the gas will build up and foul out the plugs.

A blown head gasket can leak coolant, which soaks the spark plugs and stops gas from being burnt away.

How Do You Troubleshot and Fix an Engine with a Wet Spark Plug?

The first thing to check is if the cylinder is getting a spark since no spark will cause an issue.

If there is no spark, then check the spark plug wires and coil.

Next, the fuel pressure can be checked, which, if low, is usually a symptom of a leaky fuel injector.

The fuel injector can also be swapped with a good cylinder to see if the issue follows.

If the spark plug has both gas and coolant, the head gasket has likely gone bad and needs to be replaced.

Summary
If you remove a spark plug and it is wet with gasoline, it can be caused by a few different things.

Causes include a faulty fuel injector, no fire to the plugs, and possibly a bad head gasket.

A head gasket that is bad can also cause an issue since coolant can stop the cylinder from firing.

Each component will need to be checked and tested to see which has failed.

Have you had an issue with spark plugs wet with gas? Let us know your thoughts below.

Bob Thomas
Latest posts by Bob Thomas (see all)

2 thoughts on “Causes When Spark Plugs are Wet with Gasoline

  1. John

    Great article, thanks! I changed my 2012 ford focus plugs to e3’s tonight. The middle two came out wet. Did not smell like gas but was too thin to be oil or coolant I think. It seemed to idle better after. The idle was up and down before changing but only once in a while. Runs perfectly smooth when not idling. Any thoughts?

    Reply
  2. Kassahun

    I have got a good concept about the topic. Does spark plug wetness connection with piston type carburetor of toyota Dx ?

    Reply

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