Sylvie Willis
Bosch CIS fuel injectors are mechanical injectors that are not operated by an electrical voltage on an internal injector coil. They are also known as K-Jetronic injectors. CIS stands for Continuous Injection System. Cleaning these injectors can be a hassle, and sometimes, they cannot be thoroughly cleaned by normal pressure flow cleaning. Professional injector cleaning can be expensive, but it is possible to clean them at home. This can be done by soaking them in a cleaner and then blasting them out with fuel while attached to the car. However, it is important to note that they may never run perfectly again.
Bosch CIS Fuel Injectors Cleaning Characteristics and Values Table
| Characteristics | Values |
|---|---|
| Cleaning Fluids | Techron Injector Cleaner, Lubro-Moly Injector Cleaner, Seafoam, Brake Clean, Carb Clean |
| Cleaning Methods | Soaking, Ultrasonic Cleaning, Back Flushing, High-Pressure Solvent Cycling, Fuel Blasting |
| Tools/Equipment | Compressor, Home-made Injector Pressure Tester, Professional Injection Cleaning Machines |
| Cost | Professional cleaning costs vary; DIY cleaning costs ~$30/injector + $3 for new rubber seals + ~36 for 3 cans of brake clean |
| Time | DIY cleaning took ~3 hours for 7 injectors; professional cleaning may take less time |
| Results | DIY methods may yield tolerable results; professional cleaning can restore flow rates to OEM specs |
| Replacement | Injectors with internal rust or a weak internal spring may require replacement; Bosch injectors with internal screens are difficult to clean thoroughly |
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What You'll Learn
Ultrasonic cleaning methods
Ultrasonic cleaning can be effective for cleaning fuel injectors, but it is not a simple process. It requires powerful equipment and a good deal of knowledge to achieve the desired results. The injectors must be cleaned internally, which can be challenging. One user reported that they had to "throw in" their injectors into an ultrasonic unit, but this did not clean them internally. Therefore, it is important to flow check the injectors after cleaning them with calibration fluid.
The ultrasonic cleaning process involves connecting the electricals to the injector, placing a length of clear tube over the nozzle side, and immersing the setup in an ultrasonic cleaner with an alcohol bath. The voltage is then cranked up until the injector just opens, and the tube is filled halfway with alcohol.
It is important to note that injector cleaning machines use both chemicals and pressure to clean the injectors, and they also measure spray patterns to test their performance after cleaning. Additionally, the injector nozzles need to be very close to the transducer and fired at different rates of speed at specified milliseconds, depending on the spray pattern used.
One user reported that they had success cleaning injectors with a combination of ultrasonics and CRC System 1 injector cleaner. They also mentioned that certain parts might need to be replaced, and some injectors might need to be sent out for professional cleaning.
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Using a homemade injector pressure tester
To clean Bosch CIS fuel injectors using a homemade injector pressure tester, you will first need to remove the injectors from the engine. This is because the only reliable and safe way to test them is to use a pressure tester, and doing so while the engine is running can be dangerous as atomized gasoline can easily ignite.
Once you have removed the injectors, you can begin the cleaning process. One method is to soak the injectors in a cleaning solution. Seafoam is a popular choice for this, and it can be purchased at auto parts stores. You can also try using injector cleaner or carb cleaner. After soaking, tap the injectors upside down a few times to remove any remaining crud or black gunk.
The next step is to use your homemade injector pressure tester. Connect the tester to the injector and apply high pressure. This will help to clean the spray pattern and improve the performance of the injector. If you don't have access to a pressure tester, you can try using a compressor to blow the cleaner out of the injector after soaking.
It's important to note that not all older CIS fuel injectors can be thoroughly cleaned, and some may be beyond repair. Additionally, Bosch injectors have internal screens that can be difficult to clean completely. In some cases, it may be more effective to simply replace the injectors rather than attempting to clean them.
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Cleaning with high-pressure solvent
To clean Bosch CIS fuel injectors with a high-pressure solvent, you will need to remove the injectors from the vehicle and use a specialised cleaning solution. Here is a step-by-step guide:
- Remove the fuel injectors: This step involves detaching the fuel injectors from the vehicle's fuel system. It is important to label and keep track of the parts to ensure proper reassembly.
- Inspect the fuel injectors: Before cleaning, visually inspect the fuel injectors for any signs of damage or excessive wear. Look for any cracks, leaks, or other issues that may impact their performance.
- Prepare the cleaning solution: Choose a suitable cleaning solvent designed specifically for fuel injector cleaning. Some options include Chevron Techron, Liqui Moly, or BG44k. Ensure you have enough cleaning solution to completely submerge the injectors.
- Soak the fuel injectors: Place the fuel injectors in a container filled with the cleaning solution. Allow them to soak for an extended period, following the recommendations on the cleaning product's instructions. This step helps loosen and dissolve any built-up deposits or contaminants.
- Ultrasonic cleaning (optional): For a more thorough cleaning, consider using an ultrasonic cleaner. Place the fuel injectors in the ultrasonic cleaning machine, following the manufacturer's instructions. The ultrasonic waves create cavitation bubbles that effectively break down and remove contaminants from the injectors.
- Rinse and dry the fuel injectors: After soaking or ultrasonic cleaning, thoroughly rinse the fuel injectors with a clean solvent or compressed air to remove any remaining cleaning solution and loosened debris. Ensure the injectors are completely dry before proceeding.
- Backflush the fuel injectors: Using a specialised tool, such as Kent's bench mount tester, force the cleaning solution backwards through the fuel injector. This step ensures that any remaining debris or contaminants are flushed out and that the injector is thoroughly cleaned.
- Test the fuel injectors: Before reinstalling the fuel injectors, test their performance. You can use a homemade injector pressure tester or a specialised testing device to evaluate the spray pattern and ensure that the injectors are functioning optimally.
- Reinstall the fuel injectors: Finally, carefully reinstall the cleaned and tested fuel injectors, ensuring that all connections are secure and properly tightened. Refer to the vehicle's service manual or seek professional guidance if needed.
It is important to note that while cleaning fuel injectors with high-pressure solvent can be effective, it may not always produce perfect results. Some internal components, such as the screens on Bosch injectors, can be challenging to clean completely. In some cases, replacing the fuel injectors may be the best option, especially if they are severely worn or damaged.
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Back flushing with cleaning fluid
To begin the back-flushing process, you will need to remove the fuel injectors from your vehicle. This will allow you to access the injectors and work on them without hindrance. Once removed, it is important to identify the type of injector you are working with. Bosch injectors, for example, have internal screens that can be difficult to clean thoroughly.
After identifying the injector type, you can begin the cleaning process. Attach a braided CIS line to the injector, ensuring a secure connection. Fill the injector with a suitable cleaning fluid, such as carb clean or brake clean. Allow the injector to soak in the cleaning fluid for a while, helping to loosen any stubborn deposits.
The next step is to use a compressor to blow the cleaning fluid out of the injector. This step should be done carefully, ensuring that the fluid is completely expelled from the injector. You can then repeat the process as needed, until you are satisfied that the injector is clean.
Finally, it is important to test the injectors after cleaning. This can be done by starting the car and checking for fuel leaks and proper functioning. You can also test the spray pattern and flow rate to ensure optimal performance.
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Soaking in injector cleaner
Soaking fuel injectors in a cleaning solution is a common method for cleaning Bosch CIS fuel injectors. This process can help to remove built-up crud or debris inside the injector, improving its performance and spray pattern.
To begin the cleaning process, you will need to remove the injectors from the vehicle. It is recommended to wrap the thread 360 degrees around the valve to avoid it popping off during removal. Once removed, you can attach a braided line to the injector and fill it with a carb cleaner or a dedicated injector cleaning solution, such as SeaFoam, Chevron Techron, or Liqui Moly.
After filling the injector with the cleaning solution, allow it to soak for an extended period. Some sources suggest that a quick soak and a blast of compressed air may be sufficient, while others recommend leaving the injectors to soak for months, tapping them upside down occasionally to dislodge any built-up crud.
After soaking, you can use an air compressor to blow-dry the injectors and remove any remaining cleaning solution. It is important to ensure that the injector is thoroughly dried and free of any debris before reinstalling it in the vehicle.
While this method can be effective, it may not always produce perfect results. Some injectors may still exhibit minor issues or imperfections in their spray pattern after cleaning. Additionally, it is important to note that not all older MFI and CIS fuel injectors are restorable, and if the tip is worn out or damaged, it cannot be repaired or replaced.
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Frequently asked questions
There are a few ways to clean Bosch CIS fuel injectors. One way is to soak them in a cleaner such as SeaFoam, Lubro-Moly injector cleaner, or carb clean, and then use a compressor or fuel to blast the cleaner out. Another way is to use a professional injection cleaning machine, which uses high-pressure solvent and ultra-sonic methods to clean the injectors.
The cost of cleaning Bosch CIS fuel injectors varies depending on the method chosen. Professional injector cleaning services can be expensive, but purchasing a new injector can cost even more. CIS injectors can cost under $150 for a set of four, while the cleaning process can cost 60% to 75% less than buying new replacements.
The frequency of cleaning Bosch CIS fuel injectors depends on various factors, including the usage and maintenance of the vehicle. However, it is recommended to have them cleaned or serviced regularly to ensure optimal vehicle performance.
