Frequently asked Fuel Injector servicing questions

  1. Why choose WitchHunter Performance for my injector servicing?

  2. Does WitchHunter Performance "Rebuild" injectors?

  3. What is the normal turn-around time?

  4. Why doesn't WitchHunter Performance offer an injector exchange service?

  5. What is Flow Matching?

  6. Are all injectors the same cost to service?

  7. What are the symptoms of an injector that requires service?

  8. Why do injectors need cleaning?

  9. How do I store injectors when not in use?

  10. What kinds of injectors do we service?

  11. Do we modify injectors to increase flow?

  12. Can injectors that have sat for years be serviced?
  13. Why choose WitchHunter Performance for my injector servicing?

    That's simple....We'll do an honest job for an honest price, you don't need to pay up to $35 each to get the job done right. Pretty much all the injector shops use either the ASNU or New Age injector cleaning/testing machines, and we buy from the same parts suppliers... so no shortcuts here. We keep the overhead reasonable and purchase the tools and equipment to do the job efficiently. We only have A.S.E. certified technicians doing the work on your injectors.

    We test injectors on highly modified ASNU machines and use our own custom test fluid temperature controller to help get accurate results. All testing is done using a certified flow testing fluid.
    WitchHunter Performance uses the SAE standard J1832 as a guideline for our shop methods. This is the technical standard for testing gasoline fuel injectors by the Society of Automotive Engineers.

    The owner has worked 20+ as an electrical engineer in the past, and has also worked with the injector testing machine company by testing and troubleshooting the machines. We do Beta testing and use one of the few computer controlled ASNU injector machines in the world.

    We are a full-time business and cleaning injectors is all we do. We service over a 1000 injectors a month and have the experience and knowledge to do the job correctly. New injector shops are appearing on the web all the time..... Let them practice with somebody else's injectors.

    The bottom line... We know what we are doing, and do it well.

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    Does WitchHunter Performance "rebuild" fuel injectors?

    Nobody actually rebuilds gasoline injectors, since they are a sealed unit and can't be totally disassembled. What we do is inspect, test, ultrasonically clean and replace any serviceable parts, (such as filters, o-rings, & pintle caps). Some companies call this rebuilding, or even remanufacturing and charge over 5 times our price. We replace all the parts that can be replaced. The truth is, you are getting the same thing.

    Beware of places that claim to "Rebuild" gasoline injectors.

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    What is the normal turn-around time?

    Under most circumstances we can ship 1-2 days after we receive the injectors, the current turn-times are on shown on our Home page. We return ship by priority mail as it will normally get coast to coast in 2 -3 days for a reasonable cost. Please contact us if you would like other shipping arrangements.

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    Why doesn't WitchHunter Performance offer an injector exchange service?

    We only clean our customers injectors, that way you know what you are getting. Some companies buy old used injectors by the truckload, use minimum wage labor to clean the injectors that work and throw the rest away. So you may be getting one with 30K miles and some with 400K on them in the same set. It is common practice for these places to grind off the original part number and give you an injector that flows "close" to your injector.

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    What is Flow Matching?

    It's one of those terms that get used probably too often. Flow matching is when we take a large number of injectors that are tested and then grouped others that have the same flow characteristics. They can be characterized for high RPM flow only or best all-around flow. WitchHunter Performance can test injectors to better than 1% and be repeatable.

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    Are all injectors the same cost to service?

    All injectors we service are cleaned and flow tested for $22 each. We don't charge more for side-feed or TBI injectors. There are no extra or hidden charges.

    In rare cases there are injectors that require seals that are not available through our supply channels, and must be purchased through the dealer.

    Hose-end injectors... We will have to cut off the hoses on injectors that have them attached in order to remove the internal filter and to clean them properly.

    We will charge $2.00 each for any injector that are not serviceable or spares.
    You may want to check the coil resistance of each injector before shipping if possible to verify that that are within 10% of each other. Coils can fail on any injector and especially if they are know to have coil winding issues, see our "Problem injectors" page has more information on these.

     

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    What are the symptoms of injectors that requires service?

    Dirty or partially clogged injectors can show up in many ways and may include:

    - "Check Engine" light or cylinder misfire code
    - Poor idle
    - Light throttle surging or bucking
    - Denotation (knocking or pinging), causing possible engine damage
    - Low speed hesitation and surging issues
    - Emission problems
    - Loss of performance
    - Increased fuel consumption

    Leaky injectors can cause:

    - Hard starting, especially when hot
    - Poor idle
    - Emission problems
    - Increased fuel consumption
    - Exhaust odor

    External Injector leak:

    - Are a fire hazard and should be discarded. These can not be fixed by cleaning. See or "Problem injectors" page for injectors the commonly have this issue.

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    Why do injectors need cleaning?

    Modern fuels are a complex blend of hydrocarbons and additives, many of which evaporate at different temperatures. Each time a hot engine is shutdown (heat soak), a small amount of gasoline is left on the tip of the each injector. Since the engine temperature is now above 200 degrees F, the more volatile compounds in the fuel evaporates and the less volatile elements dry on the injector tip and form solids. As time goes on, these accumulations grow and start affecting the injector spray pattern and fuel distribution.

    Both Turbo and Supercharged engines are very tough on injectors due to the higher intake temperatures and turbo oil getting past the seals and depositing on the injector tips.

    Older engines with worn rings and valve guides also contribute to the build-up. This blow-by gets introduced into the intake by the PCV system.

    Failure to change the fuel filter and allowing moisture in the gas tank both have detrimental effects on the injectors. Rust can deposit itself below the injector filter and can cause serious problems.

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    How do I store injectors when not in use?

    Corrosion is probably the injectors biggest enemy. Gum, varnish, and other normal deposits can be removed by cleaning. Since the internals of injectors are made of various steel alloys, they will corrode or rust. Once the fuel inside dries out, the deposits inside harden and the pintle can stick to the seat making it inoperable. There is enough moisture in the air in most parts of the U.S. to cause corrosion with the pintle and seat will not seal and give you a leaky injector if allowed to happen.

    If you plan to store injectors for any length of time, wipe the dirt off them and spray them (inside & out) with a penetrating oil like WD40 and seal them in plastic bags then store them in a dry place.

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    What kinds of injectors do we service?

    We can service the following type of gasoline injectors:

    - Top feed
    - Side feed
    - Throttle body
    - Motorcycle, ATV, Snowmobiles, & Marine

    What we don't service:

    - Diesel, takes completely different equipment.

    - GM Truck Vortec CPI injector "spider" assemblies. These have the plastic hoses and poppet valves.

    - GDI injectors
    , (Gasoline Direct Injection) these spray fuel directly into the cylinder and are normally used on a few high-end cars in the last 2 years.

    - CIS, injectors, these are a mechanical injector. They don't clean well due to design, and the internal filters are not replaceable. Best to replace any suspect injectors as most are in poor shape due to internal rust.

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    Do we modify injectors to increase the flow?

    Very few injectors can be modified to increase the flow and still work correctly. Usually the spray patterns will be poor and their flow rates will be very mismatched after modification.

    The only injectors we currently modify are the pink or blue top-feed Denso's and the yellow side-feeds that are used in the late model Subaru. These will typically flow within a few percent of one another after modification. We perform this operation using a lathe or mill to prevent injector damage. See our Subaru Mods page page for pricing.

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    Can stuck injectors that have sat for years be serviced?

    Injectors that are stuck closed due to non use for long periods can usually be serviced. We have better than a 95% success rate of getting them back up to spec.It sometimes takes an extra day or two in the shop for these. In some cases, corrosion has damaged them to a point where they can not be saved.

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