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If you’re experiencing poor idle, rough engine performance, reduced fuel efficiency, reduced engine power, and an exhaust that gives off unburned fuel, there’s a strong chance that it’s time to replace your fuel injectors. The principal function of fuel injectors is to spray the right amount of fuel into the combustion chamber of your engine just before the piston moves down, mixing air and fuel to run the engine. With a failing fuel injector, the right mix of air and fuel is not achieved, leading to issues in your engine. As such you should be ready with the knowledge and skills needed to replace your fuel injectors.

Safety First

Safety always comes first whenever you’re working on your vehicle. This is especially true if you’re working with the car’s engine and fuel system. The automobile fuel system is pressurized so you really need to make sure you’ve released the pressure in the fuel lines before you start disconnecting such lines. It is also wise to remove all flammable materials in your work area or any potential source of spark. Wearing protective eyewear like goggles is a must. You may also want to wear the right gloves to prevent contact with fuel and other substances under the hood.

Test Your Fuel Injectors

Even before you start disconnecting anything it is always a good idea to test your fuel injectors. There are several ways in which you can go about this.

First, you can start your car’s engine and feel for any vibrations coming from the engine. Listen for any sound or noise coming from the engine bay as well. Your engine lights can also tell you something is off.

Second, you can use an ohmmeter or automotive multimeter to test your fuel injectors. Connect the tester’s prongs on the electrical connector on the fuel injectors to give you an idea of how well these devices are working. However, since vehicles come in either low impedance or high impedance types of fuel injectors, you may want to check your car’s manual first.

Third, get a Noid light or any test light to connect with an injector. Turn up your ignition and look for flashing light on the tester. This should indicate good injector condition. If no light is emitted, you’ve got a busted injector. Make sure to check the other injectors in your system. Other testers can be used, of course.

Fourth, if you have individual injectors supplying each cylinder you can disconnect one fuel injector at a time. Crank your engine. Check if the engine runs roughly. If there is no change in the way the engine runs that means the disconnected injector is busted.

Release Pressure from the Fuel Lines

Bleed off pressure first by loosening the relief valve of the fuel lines. If you cannot find a relief valve, you can locate the relay switch or the fuse for your fuel pump. Crank your engine and let it run for a few seconds before removing the fuse. The car’s engine will keep on running until it uses up all the fuel left in the lines.

Disconnect the Fuel Rails

Most cars come with fuel rails that deliver fuel to the injector in each cylinder. Disconnect the rail’s main fuel line as well as any other line that is present at the opposite end. Remove any screws or bolts that secure the fuel rail and uncouple any related wiring. Carefully remove the fuel rails so they don’t damage your fuel injectors. Many of these are simply pressed onto the tops of injectors so you should be able to easily remove the rail.

If your car doesn’t come with a fuel rail, then you can start disconnecting the fuel injector. This is often clustered in one area found in the throttle body assembly. It would be wise to check your owner’s manual to quickly find where the throttle body is located.

Disconnect the Fuel Injectors

Each fuel injector will come with a plug that is connected to a wiring harness. Most plugs are secured with a springy wire that can be easily removed with a flat-tip screwdriver. Carefully insert the flat-tip screwdriver in the space between the plug and the spring. Give it a nudge until it comes loose.

Pull Out the Fuel Injectors

When removing the fuel injectors, it is best to do it carefully, otherwise, you damage the fuel rail. It is often necessary to inspect the nozzles of the fuel injectors especially their O-ring seals. These should be complete, if not, there’s a chance that the O-ring is still in the intake manifold. If that is the case, you may want to remove the O-ring from the manifold first before continuing with the pulling of the fuel injectors.

Depending on the model and make of your car, the fuel injectors may be secured to the fuel rail by a retainer. It is important to remove any retainer first. Sometimes, these may need to be rocked back and forth, but not so much that it may damage the rail.

Get a fuel injector puller to remove the fuel injectors from their ports. Don’t make the mistake of yanking them all out with all your might as they might break and put some of the bits into your engine. Using a fuel injector puller not only simplifies the removal of the fuel injector, it also helps preserve the integrity of your engine. To use the fuel injector puller, simply slide the gadget under the lip of the fuel injector housing. Carefully pop it out.

Be careful when removing the fuel injector as you’ll be leaving a large hole in your intake manifold. Care should be taken not to allow anything to get inside or drop inside this hole, otherwise, you’ll find fixing it can be a real headache.

If you’re working with a throttle body, then removing the fuel injectors shouldn’t be a real concern as it is as simple as prying them loose from their slots, carefully, of course.

Replace with New Injector

If your car comes with a throttle body, follow the manufacturer’s instructions in the installation of the fuel injectors into your throttle body. Make sure to install a new injector retainer bracket, as well; although the original can still be used if it’s not severely battered. Secure and tighten the retainer bracket bolts in 1/8 turns from the bolt’s center outwards. Hook up the fuel injector harnesses and electrical connectors to the fuel injectors.

If your vehicle came with a fuel rail, make sure to install new parts-specific O-rings onto the new fuel injectors. Make sure to clean any debris that may be present on these items. Carefully slot the fuel injector into the intake port of your engine. Give it a slight push until they rest securely in place. In situations where the intake manifold had to be removed, you will have to replace the O-rings or intake gasket as well before putting the intake manifold back in its place.

Install the fuel rail over the fuel injectors and tighten the bolts and screws. Next, don’t forget to reconnect the main fuel lines and other things that you have removed at the beginning of this endeavor. If you removed the engine cover, it’s time to put it back on and secured in its place.

Check for Leaks

Just because you’re done replacing your fuel injectors doesn’t mean you can wrap things up. Remember that you disconnected the main fuel line and removed the fuel rail of your car’s fuel delivery system. It is imperative that before you take your car out for a spin, you should check it first for any leaks in its fuel system.

To do this you’ll need a combustible gas detector. First, you will have to fill your lines with fuel. Turn on your ignition and listen for fuel pump activation. You’ll hear a distinct noise in the fuel pump as if it is filling up with fuel. Once the noise stops, turn the ignition off. You will need to do this about 3 to 4 times to make sure that the entire fuel delivery system is filled with fuel.

Once you’re done, you can get the combustible gas detector and place the sensor on all of the fuel line connections in your car. This will help determine if there is fuel leaking somewhere. If none is found, then you can pat yourself on the back for a job well done.

Give it a Test

Take your car for a drive around the neighborhood. Be especially mindful of the sounds or anything coming from your engine such as vibrations or the cylinders not really firing as they should. Also, check your instrument panel for engine warnings. If the check engine comes on during the test drive, it may mean you have a different problem in your car’s fuel system. Otherwise, if no warning lights come on during the test drive, you’re definitely good to go.

Replacing your fuel injectors can be quite intimidating and stressful especially if you don’t have the correct tools to get the job done. And while online instructions can provide you with direction on how you can accomplish these things, it is still best to have a professional do it for you. For maintenance, check out our review of the best fuel injector cleaners on the market.

Sources

  1. DIY Fuel Injector Replacement, ThoughtCo
  2. How to Replace a Fuel Injector, 2CarPros
  3. How to Replace a Fuel Injector, Your Mechanic

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