New Hemi Engines 2003-Present. Larry Shepard

Sensor (O2): Sometimes there is only one oxygen sensor, but newer models may have two, three, or four of these sensors that are in the exhaust manifolds, the catalytic converter, or the exhaust pipe. The O2 sensor measures the amount of oxygen in the exhaust gas. These sensors are heated. You must disconnect O2 sensors that are located in the exhaust manifolds, but an O2 sensor in the catalytic converter or exhaust pipe can remain attached.

      Air Temperature Sensor: This sensor is installed in the air intake hose, just in front of the throttle body toward the passenger’s side.

      Manifold Absolute Pressure Sensor (MAP): The manifold absolute pressure (MAP) sensor has been relocated from the throttle body to the rear face of the intake manifold. This sensor measures the pressure inside the manifold as the engine load varies.

      Electric Throttle Control Sensor (ETC): This sensor is attached to the side of the throttle body. It combines the duties of the former throttle position sensor (TPS) and the idle air control (IAC) motor. It feeds the throttle position information to the computer and adjusts the engine idle speed.

      Speed Input: This information is no longer located in the transmission extension and is not considered a separate sensor. The speed information is gained from other sensors such as the wheel speed and crank speed inputs.

      Knock Sensors: There are two knock sensors. One is located on each side of the Gen III Hemi block below the exhaust manifold. They are not technically part of the MPI system, but they pull spark advance if they sense knock (also called detonation). They are very important for supercharged engine applications and any engine using pump gas.

       Documentation Required

      Try to use the basic description of the sensor when labeling wires and hoses. Common labels include MAP, TPS, IAC, etc. ■

       The intake manifold sits on top of the engine with the throttle body mounted on the front of the manifold. The long runner tuned manifold tends to look like a beer barrel (rounded). The manifold can be made of plastic (as shown and used on the 5.7L version) or aluminum (on the 6.1L only). The throttle body can point straight ahead (as shown), be vertical, or be angled toward the left fender.

       Almost all of the production Gen III engines have an engine cover for added styling. Some are large covers that almost cover the whole of the engine compartment and some models use two smaller covers as shown. The intake manifold sits between the two “392 Hemi” covers, one on each cylinder bank. (Photo Courtesy FCA US LLC)

Pulling the Engine

      There are several basic approaches to pulling an engine. If you have a vehicle hoist, you can remove the engine and transmission together by dropping them out the bottom and raising the car above them. However, these hoists are not common in home shops. With a cherry picker, you move the engine above and away from the engine compartment. With a chain fall wrapped around an I-beam, you lift the engine and then move the vehicle. With the typical cherry picker or chain fall, it is generally easier to leave the transmission in the vehicle, but it must be supported. Remember that the engine assembly weighs around 400 to 500 pounds, so if you drop any part on your hand or foot, it will hurt. Also dropping the engine will damage it, making your rebuild even more expensive.

       Lifting the Engine

      There are few vehicles that can open the hood straight up, so removing the hood is generally the first step in an engine rebuild project. Next, drain the oil from the pan and the water and antifreeze from the radiator. These draining operations should be done outside of the work area. Once drained, move the vehicle into the work area and position it for engine removal.

      Once everything is in position, remove the large single engine cover. The two smaller covers may be left on and removed later. With either type of engine puller, there are special fixtures that attach to the engine for removal, but the most common method is to use two chains. These lifting chains or straps should not be attached to the intake manifold. Typically, the lifting chains are attached to the front and rear faces of the heads. I recommend crossing the straps from left front to right rear and right front to left rear. If the chains or straps hit the small engine covers when tightened, then remove the covers.

       Most engine rebuilds begin with the engine in a stock engine compartment. With today’s full-emission package, the engine compartment is very full with wires and hoses running everywhere. It is important to find and label all the wires, sensors, and hoses.

      If required, remove the intake manifold assembly and attach a special lifting fixture. Generally, you should remove the radiator from the vehicle. Most of the accessories will be removed, but the power steering pump, the air-conditioner compressor, the exhaust pipes, and the automatic transmission oil lines are typically set aside in the engine compartment. Bungee cords or straps can be used to hold these parts out of the way as you remove the engine assembly. Mark all hoses and wires as you disconnect these parts and put all bolts and small parts into plastic bags that are clearly marked with their name and location.

      Fuel Pressure Release Procedure

      The Gen III Hemi fuel-injection system is under constant fuel pressure of 19 to 39 psi. Perhaps one of the most important items to do in the engine removal process on the Gen III Hemi V-8 is to safely release the fuel pressure. With a carburetor, you just shut the engine off and disconnect the fuel line. With the multi-point injection (MPI) system, there is high pressure in the fuel line even with the engine off. This pressure causes us to use more caution and follow a specific procedure.

      1. Remove the fuel fill cap.

      2. Disconnect the fuel pump module electrical connector. Note: A separate fuel pump relay is no longer used; instead a circuit within the totally integrated power module (TIPM) controls the electric fuel pump located within the fuel pump module. The fuel pump module electrical connector must be disconnected.

      3. Start and run the engine until it stalls.

      4. Attempt restarting the engine until it will no longer run.

      5. Turn the ignition key to the off position. If the vehicle has keyless ignition, remove your foot from the brake and press the ignition button until it shows that it is in the off position.

      6. Place a rag or towel below the fuel line quick-connect fitting at the fuel rail.

      7. Disconnect the quick-connect fitting at the fuel rail.