Frequently Asked Questions

What is a fuel injector? How do you clean fuel injectors?

Simply put; a fuel injector is an electronically controlled valve that is either fully open or fully closed. The period the valve is fully open is measured in millionths of a second.

Injectors have the finest tolerances of any mechanical part of the engine.

What does the basic inner working parts of a fuel injector consist of?

Most fuel injectors consist of a body that houses an electromagnetic coil and a sealing mechanism such as a pintle, ball or disc. These sealing mechanisms are usually kept closed by means of a spring.

Injectors are fully open or fully closed. The amount of fuel injected is determined by how long the injector is open or by how long the pintle, disc or ball is removed from its seat.

How Does a fuel injector work?

Fuel under pressure is sprayed in a very fine mist from the tip of the injector. To achieve this, a current must flow through the injector. Contrary to popular belief, this is NOT done by sending power to the injector. Fuel injectors are normally fed power whenever the ignition key is on, but the circuit is not completed and therefore the injector is still closed. The computer controls the ground side, of the circuit. When the computer provides the injector with a ground, the circuit is completed and current is allowed to flow through the injector. This energizes an electromagnetic coil inside the injector, which pulls a sealing mechanism such as a pintle, ball, or disc away from its seat. This makes it possible for fuel to flow through the injector and into the engine. When the computer removes the electrical ground to the injector, the electromagnetic coil becomes demagnetized and a spring forces the pintle, ball, or disc shut to cut off fuel flow. Even at an engine speed of just 1000 RPM, this is done hundreds of times per minute.

What is Injector Duty Cycle?

To control the amount of fuel that enters the engine the injectors are turned on and off or pulsed very quickly. The amount of time an injector is turned on to deliver fuel is known as the duty cycle. This is measured as a percent, so 50% duty cycle indicates that the injector is held open and held closed for an equal amount of time. When the engine needs more fuel, the time that the injector stays on (its duty cycle) increases so that more fuel can flow into the engine. If an injector stays on all the time, it is said to be static (wide open, or 100% duty cycle).

What does the term static means?

If an injector stays on all the time, 100% duty cycle, it is said to be static. Injectors should never go static because control of fuel delivery is lost and this can cause catastrophic engine failure. Static injectors, or 100% IDC is normally an indication that the injector is too small for the engine. Injector duty cycle should usually not exceed 80%. Once 80% IDC is reached a bigger injector should be installed.

In some instances low fuel pressure or a failing fuel pump can cause injectors to become static. On the other hand, there are some injectors that will go static if the fuel pressure is too high.

What is an Injector’s Static Flow rate?

Manufacturers rate fuel injectors by the maximum amount of fuel that they can flow in a given amount of time at a given pressure. This measurement is known as Static Flow Rate and is normally taken at 100% duty cycle and a fuel pressure of 43.5 PSI.

Example: At 100% duty cycle a 55 pound (lb) injector at 43.5 PSI of fuel pressure will flow 55 pounds per hour.

Injector Flow Rates are expressed in pounds per hour (lb/hr) or cubic centimeter per minute (cc/min). Given the same pressure 1 lb/hr = 10.5 cc/min.

To convert lb/ hr to cc/min, multiply by 10.5
Sometimes injector flow rates are expressed in milliliter per minute (ml/min)
1 ml = 1 cc

Example: a 220 cc injector = 220 ml injector

What is impedance?

Impedance measures how easily a circuit conducts current when a voltage runs through it. Measured in ohms, impedance is a way of telling you how much of the voltage introduced at one end will really make it to the other end. Impedance depends on other qualities of electricity, such as resistance, reactance, inductance, and capacitance.
Most injectors fall into two categories: High or Low Impedance

High Impedance.

These have a typical coil resistance of 12 – 16 ohms and are the most commonly used. Drive circuitry for this type of injector is simple and sometimes referred to as a saturated driver circuit.

Low Impedance.

Low Impedance Injectors has normally a coil resistance of 4 ohms or less and is typically found in larger sized or high performance injectors. Driver circuitry for these types is called a Peak - Hold type and is more complex and costs more than the saturated type.
In a Peak - Hold system, the driver circuit allows a high current for a short time to help turn the injector on quickly. The current is then reduced to a lesser value to keep the injector open. Peak current may be 4 amps to open the injector. Once open, the current might be reduced to as little as 0.75 amps.
With the lower coil resistance, the internal spring pressure that holds the pintle closed can be increased to shut the injector quicker. This allows both faster opening and closing times and makes tuning large injectors easier.
Peak – Hold systems reduce the power requirements to the injector coil thus keeping the coils from overheating.

What keeps an Injector from overheating?

Fuel flowing through the injector helps to keep the injector cool and in most cases prevent it from overheating.

What are the symptoms of injectors that requires service?

• Failed emission
• Performance lost
• Increased fuel consumption
• Poor idle
• Surging an bucking under light throttle
• Smoke from the tail pipe
• Detonation which can lead to catastrophic engine failure
• Pollution

Leaking injectors will cause:

• Increased Fuel Consumption
• Poor Idle
• Fuel odors inside and around the car
• Hard Starting
• Poor Emissions
• Oil thinning which can lead to catastrophic engine failure
• Hydra lock
External injector leaks is a fire hazard and can not be fixed. Injectors with external leaks must be replaced.

Why do fuel injectors need cleaning?

Hydrocarbons and additives which forms part of today’s fuels evaporate at different temperatures. Small amounts of gasoline are left behind on the tip of the injectors each time the engine is shut down. Volatile compounds in the fuel evaporate while others stay behind on the injector tip and eventually form solids. These solids accumulate and eventually start effecting the spray pattern and fuel distribution which in turn can have detrimental affects on the overall well being of the engine.

Higher operating temperatures of turbo and supercharged engines are very tough on injectors, especially due to higher intake temps and sometimes reversion. The same is also true for high performance engines with large duration cams.

Many high performance air filters do not clean the air sufficiently and contributes to the fouling of injectors. Dirty fuel filters and failure to regularly replace them is also a contributing factor

Moisture in the fuel tank could eventually lead to rust being deposited below the injector filter and can cause catastrophic failure of not only the injector but in some instances the engine

Engines with worn rings and valve guides greatly contribute to the clogging of fuel injectors.

Which injector cleaning method is the best and why?

In the tank cleaners.


• Inexpensive.
• Easy to use, anyone can do it.


• It is possible that harm to injectors, seals, O2 sensors, and catalytic converters can occur due to the harsh chemicals. There are auto makers that advise against the use of such products.
• Clogged or partially clogged filter baskets, leaking injectors, weak springs, poor spray patterns and other possible problems can not be identified.
• No way of accurately knowing if any or all the injectors have been cleaned or how well each one is operating.
• Parts such as o-rings, filter baskets and pintle caps are not replaced

On the car cleaning.

• This method is used by some dealers, repair shops and quick oil change shops. A cleaning solution is forced into the fuel rail to clean the injectors while the engine is running.


• Faster Results than with in tank cleaners.


• Due to a higher concentration of harsh chemicals there is a greater risk to damage injectors, seals, O2 sensors, catalytic converters and other electronic components.
• Can dislodge particles that build up under the filter and allow them to clog the injector tip.
• Clogged or partially clogged filter baskets, leaking injectors, weak springs, poor spray patterns and other possible problems can not be identified.
• No way of accurately knowing if the injectors have been cleaned or how well each one is operating.
• Parts such as o-rings, filter baskets and pintle caps are not replaced

Professional off the car cleaning.


• Injectors are tested for coil resistance, leaks, spray pattern, and flow rate.
• Injectors are tested side by side thus allowing for accurate flow comparison.
• Proper spray patterns are visually checked and confirmed.
• Cleaning solutions are safe, biodegradable and never enter your engine.
• Cleaning method can not harm the injector components.
• New parts such as; o-rings, filters, and pintle caps are installed.
• Before and after data sheets are provided.
• Absolutely the safest and most accurate way to clean injectors


• Injectors require removal from the car and taken in or sent to an injector shop.


What will cause injectors to go bad when not in use?

The internals of injectors are made of various steel alloys that will corrode and or rust when in the presence of moisture. Large parts of America contain enough moisture to cause corrosion/rust damage. Gum, varnish and other normal deposits can be removed by cleaning but once an injector dries out and the deposits hardened inside causing a pintle to get stuck to its seat, that injector will become inoperable and in most cases not possible to clean.

Injector Storage.

From time to time injectors need to be stored. Since corrosion is probably the injectors number one enemy it is important to make sure that injectors are cleaned properly and lubricated, inside and outside, with a good quality lubricant. The injectors should then be placed in a sealed plastic bag or container and stored in a cool dry place.