Updated at: 18-07-2022 - By: Lucas

Fuel on the spark plugs is a weird problem that occurs from time to time for motorists. Low-quality fuel is frequently the blame for this issue.

The ignition system, a defective starter revolving slowly, lower compression in one or more engine cylinders, and sensors inaccurately adjusting the air flow mixture are other possible causes of the problem..

A failed attempt to start the engine is the most common cause of fuel on the spark plug. Whenever the car won’t start, fuel is pumped into the engine’s combustion chamber, making it even more difficult to get it going and causing additional damage to the engine.

What are the symptoms of a spark plug with fuel on it?

Fuel On Spark Plug (1)

If the spark plugs are removed from the engine while it is running, they will very certainly be moist from the fuel they were filled with.

  • Difficult engine start. Often, this is due to a bad or failing starter, but also the reasons may be other elements of the motor.
  • Unstable engine operation most often when the engine is cold. In this case, there may be a decrease in its dynamic characteristics.
  • The smoke from the exhaust is black and often it smells like fuel.

Causes of fuel on spark plugs

There is a lack of power in the system. There are significant current leaks in the car battery, which is in a bad state. Ignition will most likely not occur if the starter does not work properly and rotates slowly. Wet spark plugs will be the result. The problem will only become worse as more fuel is fed to the spark plugs with each unsuccessful effort.

When it’s cold outdoors, it’s extremely important to keep an eye on your battery’s health. It’s best to replace the battery if it’s showing symptoms of wear and tear.

  • Problems with the ignition system. A weak spark can be caused by problems with high-voltage wires in case of insulation failure, and also if the entire ignition system or one of the coils is damaged.
  • Bad or failing engine sensors. Failing sensors can also cause fuel on the spark plugs, although in rare cases. The electronic control unit (ECU) is responsible for the amount of fuel supplied, based on signals from a number of sensors.
  • Bad or failing spark plugs. If you have worn or damaged spark plugs, then it will more likely cause this issue, especially if the spark is poor, it will not ignite the fuel.
  • Low-quality fuel. Often the most common cause why fuel is present on the spark plug, which will lead also to increased consumption. If you see this issue on a cold engine then most likely the octane number does not match. In the warm season, low-quality fuel is easier to ignite than in the colder season.

The coolant temperature sensor, the throttle position sensor, the MAF sensor, and the crankshaft position sensor all affect the quantity of gasoline needed to start a cold engine and the overall performance of the vehicle.

It’s extremely possible that if the ECU receives the inaccurate information from those sensors, it will give the engine cylinders too much gasoline, causing the spark plugs to overheat and burn. You must first check the coolant sensor, which is the first to alert the ECU that it needs to give more fuel, and then the MAF sensor, in order to resolve the issue.

However, looking for faults in the ECU’s memory should be done in addition to checking the fuel correction data.

How to start the engine that has fuel on spark plugs?

Fuel On Spark Plug (3)

In the event that you are unable to start the vehicle.

  • Remove the spark plugs and after that, they need to be dried and calcined. This can be done at home on a gas stove. It is recommended to always carry with you another set with working spark plugs.
  • Blow out the cylinders with air. For this, an air compressor should be used whenever possible. If you don’t have one, then to dry it is necessary to completely press the gas pedal to the floor and turn the starter for 10 seconds. In this case, you also need to remove the connectors from the fuel injectors.
  • Unscrew the spark plugs and put the caps back on, and then try to start the engine again. You may need to repeat the drying steps several times, but usually, two or three times is enough.


To determine if there is fuel on the spark plugs, first check to see if the battery has low charge voltage. After you’ve put high-quality fuel in your tank, go ahead and do that.

In addition, if the issue is with the injection, a diagnostic device should be connected to the ECU and checked for problems related with faulty sensor operation.