How to clean fuel injectors

Fuel Injector Cleaning

Shouldn’t allow them to stay dirty…

Using liquid cleaners as fuel additives is easy, that’s pretty clear. However, sometimes that’s not enough to get the job done. While going to a professional mechanic is always an option to get your injectors cleaned, it’s not the only one. For those of you who like to put in the effort yourself, there’s the choice of purchasing a cleaning kit to get the job done. However, it’s not something you just know how to do by default – so the question remains:

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.
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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.

The DisAdvantage of Direct Fuel Injection…Carbon Buildup

Learn how to clean fuel injectors and prevent carbon buildup

The advantages of GDI have led to it being used by most modern vehicle manufacturers. Unfortunately, it has one major flaw: carbon buildup.

Older port-style injectors sprayed fuel into the intake manifold. This jet of fuel came from behind the valve, and it actually served to wash away some of the carbon, or soot, that built upon the valve’s surfaces. This doesn’t occur with GDI fuel injection systems.

Where does this carbon originate? Normally, the detergents in the fuel would clean the intake valves. When fuel is only sprayed into the combustion chambers, however, the oxidized fuel molecules polymerize until they are no longer soluble in the gas and precipitate out as carbon deposits. The crankcase ventilation system, which lets gasses exit the crankcase as a form of pressure relief, can also introduce additional carbon into the intake in the form of vapors from oil and fuel or other substances that make their way past air filters.

Fuel system cleaners & fuel injector cleaners can help prevent carbon buildup. What Problems Can DFI Fuel Injector Cleaners Help With?

DFI cleaning chemicals are designed to stop buildups and clogs from becoming unmanageable. These additives may remedy a number of the problems associated with GDI and SIDI systems, such as:

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1. Carbon Buildups: Chemical additives can break down existing deposits.

2. Engine Hesitation: Removing carbon prevents stumbling and misfires.

3. Rough Idle: Eliminating deposits creates smoother, more regular air flow.

4. Slow Acceleration: Clearer air intake permits a more optimal fuel-air mixture.

Will DFI Injector Cleaners Fix Everything?

DFI Fuel Injector Image

Like all fuel additives, DFI cleaners aren’t a magic bullet. Specific products might work better for certain engines, and you also need to follow their instructions properly.

Many drivers discover that they obtain the best results by combining DFI systems with other fixes. For instance, although you can install a catch can to trap debris from the crankcase ventilation system, this wouldn’t remove other sources of contaminants from the intake air. Using a DFI cleaner might still be necessary.

You can also update your engine management software, but this won’t completely eliminate buildups. Although a timing adjustment might just minimize the amount of exposure that the valves get to carbon, the best this option can do is reduce future debris accumulation. Even if your software is up to date, keeping your intake valves clean is still an essential form of supplementary maintenance.

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