Spark Plug Smells Like Gas | 5 Common Reasons & Solutions

Last Updated on May 10, 2024 by Azim Uddin

Spark plugs in your car help to ignite the engine by sparking. This should not produce any smell like a gas while igniting the car. But when a spark plug smells like gas, there is an underlying issue with the plug.

Primarily, a spark plug can smell like gas due to the following underlying reasons.

• Loose spark plug or damaged spark plug
• Damaged oil reservoir cap, or O-ring
• Improper spark plug gap
• Cold engine
• Oil leak

In this guide, I will describe the reasons behind the spark plug smelling like gas and will give their solutions. Read on to learn how you will fix the issue if it happens.

Spark Plug Smells Like Gas | A Quick Overview

Before getting into in-depth reasoning, here is a quick overview of the reasons behind the gasoline smell in the spark plug. Check them below.

Reasons	Fixes
Loose or damaged spark plug	Tighten or replace the spark plug
Damaged oil reservoir cap or O-ring	Replace the gas cap or O-ring
Improper spark plug gap	Keep the gap setting between 0.028″ and 0.060″
Cold Engine	Allow the engine time to warm up
Oil leak	Check and repair the leak

Spark Plug Smells Like Gas | 5 In-Depth Reasonings With Solution

Your car spark plug may smell like gas due to various direct and indirect reasons.

1.     Loose Spark Plug or Damaged Spark Plug

The job of the spark plug is to create proper combustion between the fuel and air mixture. A damaged or loose spark plug can’t do so properly.

Damaged or loose spark plugs cause a loss of electrical conductivity of the spark plugs. As a result, the fuel remains unburned, and you will smell a gas-like smell from the spark plug.

Aside from gas smelling, you will see the following symptoms for loose or damaged spark plugs.

• Engine misfiring
• Trouble starting engine
• Slow acceleration
• Poor fuel economy

Diagnosis and Solution

• Disconnect the battery first.
• Check for the spark plug to sit firmly. If it is loose, tighten it and check if the gas smell remains by starting the engine after reconnecting the battery.
• If not fixed, remove the spark plug, as well as the spark plug wire.
• Check damage or wear and tear in the plug and the wire. I suggest replacing both the spark plug and the spark plug wire.

See the following video on how you can easily replace your damaged spark plug.

2.     Damaged Oil Reservoir Cap, or O-Ring

The oil reservoir cap keeps the oil from evaporating. In this case, the cap is tightly seated along with the help of the O-ring of the cap.

When the gas cap or O-ring failure happens, the oil reservoir cap can’t be tightened properly. As a result, the gasoline fumes out through the spark plug and creates a smell like gas.

Diagnosis and Solution

• Check for the wear and tear of the gas cap and the O-ring by removing the cap from the reservoir.
• If you find any damage in the gas cap or the O-ring is worn out, replace them.

Here is a simple way you can replace the O-ring of the fuel cap. You can simply follow the process for the gas cap itself.

3.     Improper Spark Plug Gap

For your reference, the spark plug gap is the distance between the center electrode and the ground electrode of the spark plug. The rod in the middle of the spark plug is the center electrode, and the twisted metallic arm that reaches over the center electrode is the ground electrode.

However, when the gap between these electrodes is too small or too large, the spark plug can’t ignite the engine for proper combustion. Consequently, the unburned fuel will create a gas smell from the spark plug.

Diagnosis and Solution

• Measure the spark plug gap using a gapping tool. The gap must be between 0.028″ and 0.060″.
• If the gap is smaller or bigger than the required size, you have to adjust the gap.
• You can push down the ground electrode with the gapping tool if the gap is big. You can pry the ground electrode with the gapping tool to increase the gap if it is too small.

See how to do it in the following video.

4.     Cold Engine

If you live in a cold climate and try to start your engine after a few days, your car’s spark plug can smell like gas. This is because the cold temperature requires a rich fuel mixture to ignite the engine.

Behind the scene, the cylinder temperature reaches that cold, causing the vaporization to lower and harder the combustion.

As a result, the engine can reach its operating temperature, and the fuel can’t burn properly. So, you will get a gas smell from the spark plug.

Solution

This is not a big issue at all. You have to let your car warm up before igniting. You can use a battery blanket, a portable heater, or a block heater to warm up the car before starting.

Also, try to avoid short trips. Long trips allow the engine to reach the operating temperature properly.

5.     Oil Leak

An oil leak can cause the spark plug to smell like gas because leaked oil comes to the combustion chamber and gets mixed. As a result, the mixture of engine oil and fuel will create a smell like gas.

A damaged engine head gasket, oil hose, valve stem seal, worn-out pistons, etc can cause the leak.

Diagnosis and Solution

• Check for the damaged components and fix the oil leak. I would suggest you consult a professional mechanic to do so efficiently. It may cost you around $100 to $150.

Wrapping Up

A spark plug smells like gas, which can happen due to several reasons. Most of the reasons are solvable DIY. But an oil leak might not allow you to fix it that easily.

In this case, consult a professional. Also, regularly check for any wear and tear. Also, do regular maintenance tasks for your vehicle once a month to avoid such an issue.