Clogged Fuel Injectors

Clogged fuel injectors does not allow the flow of gasoline through them. Hence the world “CLOGGED”clogged fuel injectors

Over time injectors become clogged due to hydrocarbons, sediment and other elements in the fuel. Internal components rust due to the presence of water in the fuel. Water gets into the fuel due to the fact that the Ethanol in the fuel is hygroscopic.

Some smaller and older service stations has debris and sediment in their storage tanks and that sediment and debris which eventually can make its way to the injectors is pumped into the fuel tank. Injectors also get gummed up with varnish and gunk which formed when fuel is left in the tank for long periods of time.

Diagnosing clogged fuel injectors:

Diagnosing dead or clogged fuel injectors is difficult because it acts the same than a bad coil, dead spark plug, broken spark plug wires and or electrical problem.


  • One, multiple or all the cylinders are not firing.
  • The engine does not make power.
  • Engine does not want to start.

If possible follow the following procedure:

To diagnose clogged fuel injectors, a process of elimination should be followed.

  • Start the engine when cold and let it run at idle for 5 – 10 seconds.
  • If possible touch each of the exhaust manifolds with your bare hands and find the one that’s not warm. Do not do this if the engine is hot. If the engine is hot then drop droplets of water on the exhaust manifold or wet your hands and if possible quick touch the manifolds.
  • Remove the connector from the injector on the cylinder that is not warm.
  • Inspect the terminals of injector connector to make sure it is not corroded.
  • With an ohm meter check that there is power to the injector connector or use a Noid light. (Noid light are inexpensive and available from most auto-parts houses)
  • Confirm with an ohm meter that the injector has the proper resistance.
  • Reconnect the injector connector.
  • If a Noid light or ohm meter is not available a stethoscope or a piece of rubber hose can be used to to listen if the injector click. Place the stethoscope or rubber hose against the injector and listen at the other end to hear if the injector clicks
  • Remove the spark plug wire or disconnect the coil pack or remove the coil pack that goes to that cylinder.
  • Start the engine. It should sound the same.
  • Remove the spark plug. If the spark plug is dry then the injector does not deliver fuel to that cylinder. If the spark plug is wet and smells like gasoline then the injector on that cylinder is not your problem.

Moving the suspect injector to another cylinder is one way of diagnosing the problem. If the problem moves with the injector then Bingo. Unfortunately on some engines this can take hours to do.

If a vehicle, watercraft, motorcycle or pleasure craft sat for an extended period with gasoline in the tank,  it can be assumed that the fuel system is gummed up with bad fuel, varnish and sediment. In a situation like this the entire fuel system has to be cleaned.

How to fix a clogged fuel injector

Although there are many products such as injector cleaning additives that claim it can clean or unclog a clogged fuel injector while it is in the engine, they cannot. For any of these products to work they actually have to get inside the injector. Commonsense predicts that if you cannot get inside something how are you going to clean it.

By adding an injector cleaner additive to the fuel, the problem will most probably be exacerbated. Why? The injector cleaner has a cleaning affect on everything it touches. All the debris loosened by the cleaner is pumped to the fuel injector set that already has a problem. This makes the problem worse because more debris is pushed into the injectors or the pathway to the injectors.

Ultrasonic cleaning of a clogged fuel injectors

The only guaranteed method that addresses these problems and can clean a clogged injector properly is by removing the injectors from the engine. Once removed, the injectors can be dropped off or mailed to a professional injector cleaning service such as Injector RX.  Injector RX use manufacturer approved equipment and an ultrasonic fuel injector cleaning process to clean fuel injectors. Once cleaned the fuel injectors are flow tested to confirm that they spray correctly and that the deliver the right amount of fuel. The advantages of this method allow Injector RX to fully clean each injector, replace worn parts with new ones and test each injector for fuel flow comparison.

Lets us help you save money and time. Therefore before you decide what to do we strongly suggest you first read this article on the various fuel injector cleaning methods.

Dead Fuel Injector:

A dead fuel injector is an injector that does not have resistance and does not respond to electrical input.

Dead fuel injectors cannot be repaired and should be replaced with a similar unit.

It must be noted that all the above is the same for marine as well as motorcycle fuel injectors