Automotive technology is evolving at an astounding rate. It is important for the car owner and the automotive technician to have useful resources and news about the development of the integral systems that make the automobile work. This fwicki was created to provide useful news, videos, and information about fuel injection technologies.
A Cutaway View Of A Fuel Injector |
Fuel injection is a means of metering fuel into an internal combustion engine. In modern automotive applications, fuel metering is one of several functions performed by an "engine management system". For gasoline engines, carburetors were the predominant method to meter fuel before the widespread use of fuel injection. However, a wide variety of injection systems have existed since the earliest usage of the internal combustion engine.
The primary functional difference between carburetors and fuel injection is that fuel injection atomizes the fuel by forcibly pumping it through a small nozzle under high pressure, while a carburetor relies on the vacuum created by intake air rushing through it to add the fuel to the airstream.
The fuel injector is only a nozzle and a valve: the power to inject the fuel comes from further back in the fuel supply, from a pump or a pressure container.
The fuel injector acts as the fuel-dispensing nozzle. It injects liquid fuel directly into the engine's air stream. In almost all cases this requires an external pump. The pump and injector are only two of several components in a complete fuel injection system.
Periodically, fuel injectors need to be serviced or replaced. The following tips will help the technician or mechanic understand general procedures involved in replacing fuel injectors:
How To Remove And Re-Install Fuel Injectors:
The following is a general overview of how to remove and replace worn or damaged fuel injectors. This process is not recommended for the novice or intermediate mechanic or automotive technician. If you are unsure about any of the steps and techniques listed below, be sure to consult a professional auto repair technician. Due to the complexity of most fuel injection systems, it is advisable to enlist the help of a certified automotive repair technician. The example given below is a general approach and your particular make and model vehicle may require specific variations of the following procedures.
Pre-Removal Steps And Techniques:
- Relieve the fuel-line pressure. Remove the fuel pump assembly access cover. Disconnect the electrical connector by pressing down on the tab and pulling forward. Try to start the car, it should not start.
- Disconnect battery negative terminal.
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- Remove the rear intercooler pipe completely and stuff clean rags into the top of the turbo and the open IC pipe.
- Disconnect the Y-pipe from the throttle body. This may require loosening or removing the two intercooler pipes attached to it, depending on your setup, and the air by-pass hose.
- Remove the bolt holding the oil supply line near the rear turbo for more working space.
- Remove the accelerator cable bracket and set aside. Note the tension of the cable and/or the location of the bolts in the bracket for the installation later.
- Remove the two bolts that hold the 3-plug bracket on the passenger side of the plenum.
- Remove the two bolts holding the fuel injector harness to the plenum.
- Remove the passenger-side bolt from the EGR pipe (it comes up from the rear cat near the oxygen sensor). Loosen (but do not remove) the driver-side EGR pipe bolt, and slide the metal gasket downward. Securely attach a wire to the gasket, then remove the remaining EGR pipe bolt. Set the gasket aside, it can be reused.
- Carefully remove the two bolts attaching the rear of the plenum to the brackets.
- Remove the three bolts from the plenum front, the two long bolts from the plenum top, and the two nuts from the plenum front sides. The plenum may pop a little with the release of pressure.
- Carefully lift the plenum straight up to clear the front studs then tilt toward the passenger side. Prop it up. The fuel pressure regulator hose will probably slide off the throttle body, but the rest of the hoses (including the clutch vacuum assist hose on the right side of plenum) should allow enough length to move the plenum around without a problem.
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- Cover the intake manifold with a clean rag. Be sure to protect the intake manifold opening, do not allow any object to drop into the intake. Now is a good time to replace the gasket if it needs it.
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Removal Steps And Techniques:
- Remove the PCV hose from the driver's side of the valve covers.
- Disconnect the rear EGO sensor electrical connection near the middle of the front rail.
- Drain a little coolant, just a few ounces, into a clean container. Remove the overflow tube from the radiator fluid filler neck.
- Remove the hoses from the fuel pressure regulator. Remove the vacuum hose and re-attach it to the tube on the throttle body. Slide off the fuel return line hose and set aside.
- Remove the bolt that clamps down the high-pressure supply line a few inches from the from rail.
- Disconnect the 3 electrical connectors from the 3-plug bracket that you removed earlier from the passenger-side of the plenum.
- Remove the 4 bolts that secure the two fuel rails to the manifold. Be careful to not let any of the 4 insulators fall off. They are grooved to fit into the rail on top and the manifold on the bottom. Just lift the each rail up a little and slide out each insulator. The injectors should come up with the rails and the fuel injector insulators will either be attached to the injector base or remain in the manifold.
- Gently slide each injector from the rail with a slight twisting motion. Some fuel may drain out.
- Retrieve any injector insulators that remain in the manifold if you are going to replace them. Forceps work well for this.
- Disconnect the injectors from the wiring harness. Pry off each retaining clip. It may help to place your left thumb lightly over the clip while you pry it out with the thin-blade of a pocket knife.
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Installation:
Before installing the new injectors, test each injector for electrical resistance across the terminals. The standard is 2 to 3 Ohms.
- Connect the new injectors into the wiring harness.
- Place the injector insulators into the manifold recessed areas. You could also slide the insulators onto the injectors, however, you may find it easier to ensure good alignment by putting them into the manifold first.
- Slide the injectors into the rail with a slight twisting motion. First, apply a very small amount of clean motor oil on the o-ring and top of the grommet. A Q-tip will work fine for this purpose. Be sure that no oil gets into the injector.
- Roughly align the injectors with the holes in the manifold. Don't press down yet.
- Add the four rail bolts and insulators. Don't drop the insulators into the manifold.
- Now simultaneously align and insert all six injectors. Take your time and re-check continuously. Keep pressing down until the rails fit tightly to their insulators and the injectors are seated on their insulators.
- Tighten the four rail bolts using a torque wrench applying 10-13 N-m (7-9 ft-lbs). Be careful not to strip the threads.
- Re-connect the coolant overflow tube.
- Re-attach the high-pressure fuel supply line bracket.
- Re-attach the fuel return line hose to the fuel pressure regulator.
- Connect the PCV hose and the 3 connectors on the bracket that sits on the passenger's side of the plenum and re-connect the rear EGO sensor.
Post-Installation:
- Clean the plenum-to-manifold gasket if required or replace it.
- Lower the plenum onto the manifold studs. Do NOT attach bolts or nuts at this time. The plenum will have to be loose for the next step.
- Bolt the plenum to the rear two stays first. You may need to apply your weight or tap the plenum with your fist to get the holes to line up. Be sure to re-attach the grounding cable and oil pipe bracket with the driver-side stay. Insert the two bolts by hand and tighten but do not torque down.
- With the wire still attached to the EGR pipe gasket, insert the driver-side bolt through the EGR pipe and gasket and into the plenum. Tighten a little by hand. Remove the wire, slide the gasket around, and insert the other bolt. The two EGR bolts can now be tightened (18 N-m).
- Install the forward plenum bolts and the two nuts. Torque the two rear stay bolts, the front five bolts and two nuts to 18 N-m.
- Now proceed with pre-removal steps 8 to 3 above (in reverse order). Be sure to check the fuel pressure regulator hose and the other vacuum hoses.
- Re-connect the fuel pump electrical connector.
- Re-connect the battery negative terminal. The disconnected battery reset the ECU.
- Start the car and let it idle for a few minutes and check for leaks or other problems.
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