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ОглавлениеCHAPTER 2
IS IT TIME TO REBUILD?
There are many reasons to decide that it’s time to rebuild an engine, but typically the engine will give you a sign that will get your attention and convince you that it is time to get the wrenches out! Some of the key signs include high mileage, high oil consumption, oil leaks, or a smoking engine. Ominous noises are always good at getting our attention too.
These concerns can be grouped into three categories: performance-based (fuel economy or acceleration), mechanical (noises), and oil or lubrication (leaks or smoking). Another reason for a rebuild is an enthusiast is interested in a street rod, street machine, and/or custom build using the high-tech Gen III Hemi engine. An engine rebuild is a major project that will result in some downtime. However, it could pay for itself fairly quickly. A basic rebuild of a 2004 Gen III Hemi in a 2004 model that came with the engine is pretty straightforward. A 14-year-old engine is probably less expensive, but it may need to be rebuilt before an engine swap is completed. With any used engine, the history is unknown, so I would recommend a rebuild. You don’t want to take any chances.
Troubleshooting
When asking yourself if it is time to rebuild your Hemi engine, the answer should be based on mileage and tests indicating that a problem exists. High mileage alone may not require a rebuild if a maintenance cycle has been followed. Engine problems don’t always make noise. The loss of power and/or fuel economy is tough because it requires you to keep track of the engine performance over time. The key is to never rush into a rebuild. You should try to narrow down the problem with some specific tests.
The Gen III Hemi has been in production since 2003, so there should be lots of high-mileage examples around that need rebuilding. This 2006–2011 6.1L version averaged about 20,000 miles per year. There may be some of these in the pool too. The aluminum intake manifold was only used on the 6.1L engines.
Pro Mechanic Tip
Electrical concerns, such as an engine not starting, is usually related to the battery, the charging system, or the wiring. Any electrical problem would need to be fixed before any testing, engine rebuild, or engine change. ■
With a failed engine you know that you will have to rebuild it or replace it to remedy the situation. In either case, the engine is coming out and going to be disassembled. However, if the engine is still running, you should run some basic tests before you make your final decision. There are five tests that can be performed. They are: the spark plug test, the head gasket test, the compression test, the leak test, and the ECM sensors test based on on-board diagnostics called OBD II.
In the old days, early engine tests relating to performance would have been based around the carburetor and distributor. Gen III Hemi engines have neither of those components. Perhaps a hunt for vacuum leaks would be the first test, but they are not as common on MPI engines. In the Hemi engines, if you run a leak test, you can skip the compression test. If you run the compression test, the leak test will still add information that you didn’t gain from the compression test.
Spark Plug Check
The spark plug test is one of the first to perform because it does not require any special gauges and should be the easiest to do. The spark plug check can be done early on or at the same time as the compression test or the leak test. Spark plugs tend to last much longer in the MPI-based engines than they did in the carburetor/distributor era. With the intake manifold and MPI used on the Gen III Hemi engines, actual fuel distribution problems (one cylinder rich, one cylinder lean) don’t tend to pop up.
One of the unique features of the Gen III Hemi production engines is that the vehicle has an engine cover, as do many V-8s. These covers are added for styling purposes only and offer a lot of customizing opportunities. When you open the hood of the vehicle, what you see is not the actual engine but a cover or covers.
The engine covers are not related to the actual engine’s valve covers. However, the push-on posts that are used to mount the cover are actually fuel-rail attaching screws. There are two posts per side. These engine covers will have to be removed so you can get to the spark plugs.
For styling purposes, engines have been covered with a removable plastic cover. The engine shown has a large cover; some engines have two smaller covers. You can’t do much troubleshooting until these covers are removed and you have access to the actual engine components. (Photo Courtesy FCA US LLC)
The Gen III Hemi spark plug is unique because it has a 1-inch thread depth rather than the 3/4-inch depth used on the Gen II Hemi and all Mopar small-blocks. The troubleshooting tests focus on the end or tip of the plug. Some engine builders use a magnifying glass to look at the electrodes more closely.
Next, remove the eight spark plugs (one per cylinder since all Gen III Hemi engines feature dual plugs). The Gen III Hemi plugs are 1-inch reach plugs rather than the Gen II Hemi and Mopar small-block 3/4-inch reach plugs. When you remove them, keep them in order (1-3-5-7-2-4-6-8) then look at each one closely. There are about eight aspects to the plug’s potential failure listed in the plug manufacturer’s guide. What you are looking for is one or two plugs that don’t look like the others. Check for one that is black and/or sooty, looks oily, or smells of fuel.
Pro Mechanic Tip
Vacuum leaks are the number-1 drivability problem. It is a good idea to check all the vacuum hoses and connections, but it is not an official troubleshooting test. ■
Head Gasket Test
If the head gasket fails, the engine should be rebuilt. That is because in order to replace the head gasket, you have to remove the cylinder heads, and if you have the heads off the engine, you might as well look at the whole engine and not just the head gasket.
The head gasket can fail in one of two ways: from adjacent cylinder-to-cylinder or from cylinder-to-water jacket. The adjacent cylinders in a V-8 engine are 1-to-3, 3-to-5, 5-to-7 on the left bank and 2-to-4, 4-to-6, and 6-to-8 on the right bank. They are most prone to fail because they have the thinnest support area and the highest loads. The area from the combustion chamber to the oil feed or the oil feed to water could also fail, but this is less common.
To test for adjacent cylinder failure, run the compression test outlined in the next section. If a gasket failed in this manner, you will see a 50- to 70-percent loss in compression pressure.
An observation test to detect failure to the water jacket is easy to execute, but it is not as accurate as the compression and leak tests that require special gauges. To perform the observation test:
1 Remove the pressure cap from the radiator.
2 Start the engine and allow it to warm up until the thermostat opens.
3 Look for bubbles in the coolant in the radiator, which indicates a large combustion pressure leak exists.
Compression Test
The third engine test is the compression test, which requires an inexpensive compression gauge. Nearly every engine builder has one. The compression test is best run after the engine is warmed up, but it also can be done cold because you are looking for differences not absolute values.
Special Tool
It is helpful to keep a battery charger hooked up to the battery during this compression test to ensure that the cranking speed (RPM) for each cylinder is maintained for each cylinder. The RPM that the starter turns the engine over will factor into the compression gauge reading. ■
With the simple head gasket test, you don’t usually get to look at the actual gasket. This can only be done at the disassembly step. Note the extra row of smaller head bolts across the top of the gasket.
There are several styles of compression gauges. This one has a short piece of hose that threads into the spark plug holes. The extra-long reach of the plug shouldn’t cause any problems as long as the O-ring seals to the plug seat. The actual gauge connects to the hose with a quick-connect fitting (on the end of the short hose) a few inches above the valve cover. Only remove one spark plug.
All Gen III Hemi engines have dual 1-inch reach plugs rather than the shorter 3/4-inch reach plugs. For this test you only need to remove one plug per cylinder. The typical compression gauge fitting is designed to work in the shorter plug heads, but it should work fine with the extra clearance as long as the O-ring on the fitting seals to the head.
Compression Test
1 Remove the engine cover(s) to access the coils and plugs.
2 Run the engine up to normal operating temperature (180ºF) and then shut off the engine.
3 Disconnect the eight coil wires and remove the eight coils (two bolts).
4 Remove eight spark plugs (one per cylinder).
5 Remove the air cleaner.
6 Hold open the throttle blade on the single throttle body (1/2 throttle to wide open) to allow air in.
7 Thread the compression tester into the cylinder number-1 spark plug hole.
8 Crank the engine over on the starter for at least four cycles.
9 Write down the maximum gauge reading for cylinder number-1.
10 Repeat this procedure for all seven remaining cylinders.
Compression readings should be uniform in all eight cylinders with less than 20 to 25 pounds variation, from best to worst. If the head gasket is leaking (cylinder-to-cylinder), it can cause a loss of 50 to 70 psi in pressure. The engine’s mechanical compression ratio, camshaft duration, displacement, and other specs also affect the numbers but should affect all cylinders equally. The absolute gauge reading is not as important as the indication that any cylinder is way below the average.
| Engine | Gauge Pressure | Acceptable Pressure Variation |
| 347–392 | 140 psi | 25 psi |
| 393–426+ | 150 psi | 25 psi |
Documentation Required
Keep a notebook for any engine that you rebuild. Give the engine a name or a number so you can keep rebuilds straight. As you take pieces off the engine, put all of your observations and measurements into the notebook. ■
Pro Mechanic Tip
Similar to the compression test, you only need to remove one of the Gen III Hemi’s dual plugs for the leak test. Remember that the Gen III Hemi engines use a longer 1-inch reach plug. The tester’s fitting should work fine with the extra clearance as long as the O-ring on the fitting seals to the head. ■
The leak tester connects to a compressor or shop air at 90 to 100 psi (not visible). The short piece of hose with quick-connect fitting threads into the spark plug hole and the gauge connects to the hose using a quick-connect fitting. The gauges show the incoming air pressure (top left), which would be shop air, and the amount of leakage in the cylinder (top right).
The chart below shows some approximate compression pressure readings with the engine warm, all plugs removed, throttle open, and the battery fully charged.
Leak Test
The fourth engine test is the leak test, which is similar to the compression test. The leak test will give you more information than the compression test but the leak test gauge is less common, more expensive, and also requires 100-psi shop air supplied by a compressor. The leak test is best to run after the compression test or by itself.
Run the leak test after the engine is warmed up. Always write down the test results in your engine build book. To perform the leak test:
1 Remove the engine cover(s).
2 Warm up the engine to normal operating temperature (180ºF to 200ºF) and then shut off.
3 Disconnect the eight coil wires and remove the eight coils (two bolts per coil).
4 Remove eight spark plugs (one per cylinder).
5 Rotate the engine to top dead center (TDC) on the number-1 cylinder, which is the end of the compression stroke where both valves are closed. The Hemi has no distributor and no timing marks, so this may require removing the valve cover. Then mark or tape the damper and front cover’s TDC for future reference.
6 Connect the leak test gauge to shop air (90–100 psi).
7 Screw the test fitting into the number-1 spark plug hole.
8 Connect the hose fitting to the leak test gauge (typically a quick-disconnect fitting).
9 Remove the radiator cap.
10 Remove the air cleaner.
11 Remove the crankcase filler cap or breather.
12 Turn shop air on, which applies full air pressure to the selected cylinder. Be sure that the 90 to 100 psi shop air maintains its pressure throughout the test.
13 Listen for air escaping from the carburetor, crankcase, headers, throttle body, and/or exhaust manifold.
14 Look for bubbles in the radiator water.
15 Repeat this procedure for the other seven cylinders. Because there is no distributor or timing marks, use the engine’s firing order sequence (1-8-4-3-6-5-7-2) and 90-degree rotation to completing this step. To do that, rotate the engine 90-degrees from the TDC mark and install the test gauge into the spark plug fitting of cylinder number-8, which is the next to be tested. Once completed, rotate the engine another 90-degrees and test cylinder number-4, then 90-degrees and test cylinder number-3. Then follow the same procedure for number-6, then number-5, then number-7, and finally number-2.
When troubleshooting, you will find that an engine will always lead a small amount. A lot of air escaping through the throttle body indicates a poorly seated or a bent intake valve. Air escaping through the tailpipe or header indicates a bad or a burned exhaust valve. Air bubbling into the radiator indicates a blown head gasket or air escaping through the water pump outlets. Air in the crankcase (listen at the valve cover breather) indicates a bad ring or ring seal.
One of the nice features of a leak test gauge is that it gives you a numerical answer for how bad a leak is: 3 percent, less than 10 percent, 15 to 20 percent, more than 30 percent, etc. Similar to the compression test, all cylinders should be close to the average in leakage number. Leak test gauges vary, so always try to use the same gauge when you make leak test comparisons. Write down your results.
Ask the Engine
Production MPI engines can troubleshoot problems by scanning the engine control module (ECM) to find out what may have failed. This is done using the on-board diagnostics (OBD II) system. The federal government required all vehicles to have OBD II beginning in the late 1990s, and all Gen III Hemi engines have one. These computers have special features based on modern electronics and depend on multiple sensors to run properly.
The OBD II system can tell you which component has failed as well as other important information on a used vehicle. The ECM can’t tell you if you need a rebuild. The OBD II reader is an expensive tool, and one that is not commonly found at repair shops. This test may have to be done at a Chrysler dealership service department, and it can be costly.
When rebuilding an engine, it is very important to handle the OBD II sensors with care. You must locate them, disconnect them, and label all wires. They must all be reconnected once the rebuild process is complete.
The engine control module (ECM) or computer is basically flat and about the size of a book. It mounts to the engine compartment’s firewall by three bolts. The two plugs have lots of wires coming into the wiring harness plug (about one wire for each pin). Half of the pins are shielded from view by the lower wall of the plug. It doesn’t need to be removed for a rebuild project. One unique feature of ECMs is that they are based on on-board diagnostics (OBD II), and if you have a OBD II reader, you can ask it if anything is wrong and it will answer. Generally, a Chrysler dealer has the readers required.
Tools Required
You’ve run your tests and determined it is time to rebuild your Hemi. With any project as complicated as an engine rebuild, you will need a lot of tools (some common and some special).
Basic Tools
These tools are commonly used in many different projects, not just engine building. The basic tools required are as follows:
• Complete socket set (metric)
• 3/8-inch and 1/2-inch ratchets, extensions, and universals, plus deep-well sockets and speed handles
• Wrenches, open and box (metric)
• Assorted screwdrivers, pliers, and locking pliers
• Mechanics mirror with extendable handle
• Mechanics magnet with extendable handle and a pick-up tool
• Thread chasers
• Dead-blow plastic mallet
• Brass drifts (punches)
• Feeler gauges
• Assorted scrapers
• Breaker bar with a long handle
• 3/8-inch and 1/2-inch torque wrenches in ft-lbs and in-lbs
• Engine hoist (can be rented if unable to purchase)
• Engine stand
• Oil dry
• Bags for cataloging and storing parts
• Paper towels
• Engine assembly lube
• Small LED flashlight
• 6-inch and 12-inch steel scales and straight edge (24 inches or longer)
• Air tools are helpful for removing and installing flexplate and flywheel bolts (use with hardened 1/2-inch sockets and extensions). Always use caution when using air tools during assembly or disassembly. I only recommend using air tools for removing and installing the flexplate and flywheel. During engine assembly, your air tools should not be used. All final fastening or torque applications should be done by hand with a wrench, ratchet, or torque wrench.
• An air compressor is not a required tool; it is considered a luxury item.
• A digital camera doesn’t take the engine apart, but photos can show you exactly how something went together before you took it apart so you know what goes where at reassembly.
Tech Tip
Metric bolts are used throughout the Gen III Hemi engines except for the bellhousing, which may be a mixture. Be sure that your sockets and wrenches are metric sizes. ■
Mechanics mirrors (top two) can be quite handy when looking inside the engine. The extendable magnets (bottom two) are needed to retrieve a dropped nut, screw, or bolt from somewhere that it should not be.
Generally, you would not need a dead-blow hammer (top) until you install the piston-and-rod assemblies, but they can be helpful during engine disassembly. The same is true for the brass drifts (middle), which can be used to focus the hammer blow to a small area. The feeler gauges (bottom) are used to measure small clearances, such as spark plug gaps in the 0.035-inch area and rod side clearances that run in the 0.005- to 0.015-inch area. Ring gaps are also measured with feeler gauge.
You will need a variety of torque wrenches, including 1/2-inch drive (top) and 3/8-inch drive (bottom). Additionally, you need to torque wrenches that read ft-lbs (the top three) and others that read in-lbs (bottom two). It is easier to torque head bolts and main cap screws with a long handle on the torque wrench (top).
You will need measuring devices, including dial vernier calipers (top two), a straight edge (middle), and 6-inch and 12-inch steel scales (bottom).
Engine Building Tools
The following tools are needed specifically for engine building and rebuilding. They probably would not be used in other non-engine projects.
• Degree wheel and pointer
• Bridge with dial indicator
• Three-finger gear/damper puller
• Damper installation tool
• Oil passage/water jacket brush kit (assortment)
• Cylinder head stands (2)
• Piston ring expender
• Piston ring compressor
• Valve seal installer
• Plastigauge
• Top Dead Center (TDC) positive stop (optional)
• Band compressor
• Rod guides (brass or plastic)
• Scribe or permanent marker
• Ridge reamer (optional)
• Valve spring compressor
• CC-ing equipment (burette, plate, colored fluid, bridge and dial indicator, degree wheel, and pointer)
• Valvetrain organizer
• Tappet holder
• Camshaft guide (optional)
An air tool is very handy for removing or installing flywheel bolts and/or flexplate bolts. This is done before the engine is bolted to the stand. To properly and safely use an air tool, you should have hardened sockets and extensions.
The ring expander (left) is only used for removing or installing the top two compression rings on the piston. The ring compressor (right) and its Allen wrench are only used to compress the rings once installed onto the piston to allow the assembly to be installed into the cylinder.
There are several styles of tools used in removing and installing the piston-and-rod assemblies. The band compressor (upper left) is used to compress the rings at piston-and-rod installation. The long black U-shaped tool’s ends are placed over the rod bolts once the cap are removed (inserts into the beam on the Gen III Hemi), and then the flat side provides a surface to exert force on in order to get the used piston and rings to move past the ring at the top of the cylinder bores. The long and short plastic tubing and the long tubing with a wooden dowel insert (middle) are used during the piston-and-rod installation to guide the rod past the crank and to protect the crank from nicks and scratches caused by the rod. The scribe and two markers (bottom) are required to label the rods and caps because you are not supposed to number stamp them for identification.
Some tools will probably only be used for building engines. The bridge with dial indicator (top) is used for finding deck heights (top of piston to top of deck) and for finding the piston dome/dish heights, which are very important in determining the engine’s compression ratio. The degree wheel and the bent coat-hanger pointer (bottom) also fit in this engine tool category.
The tools required to measure a combustion chamber in the cylinder head are very unique and not used for anything else. The long tube is the burette, which measures the volume of fluid used to fill the chamber. The clear, square plastic plate with a hole in it (middle left) is used to seal the chamber and allow it to be filled with fluid. The CC-ing fluid (rubbing alcohol) and food coloring (red) are in the upper left. The bridge and dial indicator are used to measure the piston drop if a dished or domed piston is used. The degree wheel and the pointer are used to centerline the camshaft. In the lower right, there is a small, L-shaped piece of coat-hanger. It was cut and bent to size. It is used to hold the camshaft tensioner back away from the chain during disassembly. It will stay there until the engine is reassembled.
Extra Precision Tools
There are few do-it-yourself projects outside of engine building that require precision in the 0.001-inch area. Extra precision tools are as follows:
• Dial indicator with magnetic base
• Bridge with dial indicator
• Depth micrometer or ring squaring tool
• Dial bore gauge (optional)
• 0-1-inch, 1-2-inch, 2-3-inch, 3-4-inch, and 4-5-inch micrometers
• Snap gauges
• Dial/Vernier calipers
• Valve spring tester (optional)
• gram scale (optional)
Work Space
You will need to prep your work space for disassembly of the engine. Remember that the engine is large, and it takes up more space as you take it apart. Spend some time planning where you will place the two heads, the crankshaft, the intake manifold and its hardware, the valve covers, and eight piston-and-rod assemblies.
Vehicles can weigh 3,000 to 5,000 pounds with the engine alone weighing 400 to 600 pounds, so safety must be your top priority to avoid injury. Get jacks and jackstands lined up and decide on a transmission support as you plan your project. Also gather wheel chalks to keep the vehicle from moving until you want it to.
Also remember that you will be working with gas and oil and you need to use extra caution. Keep a fully charged fire extinguisher handy, and any oil or gas removed from the engine or used during assembly should be properly recycled.
For precision measurements, you will need a selection of micrometers: 0–1 inch, 1–2 inch, 2–3 inch, 3–4 inch, and 4–5 inch. The snap gauges (upper right) are used with the micrometers to measure inside diameters, while the micrometers themselves measure outside diameters. The diameter of the 392 piston (4.09 inches) would use the 4–5 micrometer. The diameter of the cylinder bore that the piston came out of is transferred to the snap gauge and then measured by the micrometer.
If you are going to inspect the engine parts, you are going to need a dial indicator along with a magnetic base (left) and a bridge (right). You can use one dial indicator and switch from one mount to the other, but I prefer to have two separate tools.
If you plan to measure the cylinder bores, you will need a dial bore gauge (top). This step is often left to the machine shop. The depth micrometer (bottom) is used to set the ring height in the cylinder bores when you want to gap the rings (measure the end gap).
Multi-Point Injection (MPI)
The multi-point injection (MPI) system is easy to work with, especially the factory system that is used on all of the Gen III Hemi engines. A basic rebuild would use the same sensors, so it is mainly identifying and protecting the existing sensors. It can be more complicated if you are making a conversion or a custom installation. For example, if you install a 2003 Gen III Hemi into a 1968 B-body, then you must take all the MPI hardware (sensors, wiring, etc.) with it. That style of engine swap is not as easy as installing a 1968 Gen II Hemi into a 1958 Chrysler product. The 1968 engine comes with a carburetor and distributor, while the Gen III engines have neither.
The basic hardware in any high-tech MPI system includes the fuel rail, injectors, the throttle body, and the intake manifold. There are also eight sensors that must all be wired in and operating for the ECM to know what’s happening with the engine so everything works properly.
Fuel Rail
With any V-8 engine, the typical fuel rail system consists of two sides and a crossover. The fuel rail assembly attaches directly to the intake manifold. There is a fuel pressure relief and a pressure regulator that have been moved from the fuel rail into the gas tank.
Once fully assembled with the entire engine harness hookup, it is hard to find the fuel rail on production engines. First, locate the two round push-on posts (middle of photo above valve cover screws) and the silver fuel rail behind them. There are three injectors visible below the fuel rail and seated into the intake manifold at the manifold face. Each injector is connected to the engine wiring harness using a red-and-black connector. Most of the production units use a hose crossover that goes across the top of the intake manifold at its middle and extends to the upper right to connect the two sides. Other versions connect across the front or rear ends of the main rails.
The throttle body is mounted to the front of the intake manifold with four screws. Two of the eight sensors that feed information about the engine to the computer are in the throttle body. The electric throttle control is at the front of the manifold (center) and the air temperature sensor is at the lower left. Unplug each one and tag them before pulling out the engine.
Injectors
For production Hemi engines, there is one injector per cylinder. Each is located at the intake manifold interface and is held in place by the fuel rail. The injectors should be removed with the fuel rail as an assembly.
Throttle Body
The throttle body also mounts directly to the intake manifold. It should be removed with the intake manifold and unassembled separately at a later time. The throttle body has several sensors attached to it, and they should be left as is unless they have failed.
Intake Manifold
The fuel rail, injectors, and throttle body stay attached to the intake manifold and are removed as an assembly once the engine is on the stand. The intake manifold and throttle body assembly hold more sensors than any other part of the engine. The sensors themselves do not have to be removed from the manifold or throttle body unless they are damaged or have failed.
Sensors
The production Gen III system has eight sensors that feed information to the computer. The aftermarket multi-point injection (MPI) units use a similar number. As you rebuild the engine, you will remove these sensors with the exceptions of the speed sensor and the O2 sensor. These sensors stay in the car if only the engine is being pulled.
The engine wiring harness stays in the vehicle. Be sure to label all wires and hoses to each sensor as it is removed or disconnected. Tag them using masking tape and black marker. All wires will tend to look the same at engine reinstall.
Crank Position Sensor: This sensor is located on the passenger side of the block at the rear edge of the number-8 cylinder. This sensor counts the number of teeth on the crank wheel (32 or 58).
Cam Position Sensor (CMP): This sensor is located on the passenger side of the front cover, and is even with the camshaft centerline.
Engine Coolant Sensor (ECT): This sensor is located in front of the intake manifold next to the thermostat housing. It tells the computer the temperature of the engine so it can adjust the fuel level and spark advance.
Oxygen 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.
