Emergency Care and Transportation of the Sick and Injured, Tenth Edition s2

Fundamentals of Automotive Technology: Principles and Practice Chapter 10: Engine Mechanical Testing

Chapter 10 Engine Mechanical Testing NATEF Tasks Engine Repair General • Complete work order to include customer information, vehicle identifying information, customer concern, related service history, cause, and concern. AST, MAST (p 262) • Research applicable vehicle and service information, such as internal engine operation, vehicle service history, service precautions, and technical service bulletins. MLR, AST, MAST (p 262) • Inspect engine assembly for fuel, oil, coolant, and other leaks; determine necessary action. MLR, AST, MAST (pp 264–267) Engine Performance General • Perform engine absolute (vacuum/boost) manifold pressure tests; determine necessary action. MLR, AST, MAST (pp 268–270) • Perform cylinder power balance tests; determine necessary action. MLR, AST, MAST (pp 270–272) • Perform cylinder cranking and running compression tests; determine necessary action. MLR, AST, MAST (pp 272–275) • Perform cylinder leakage tests; determine necessary action. MLR, AST, MAST (pp 275–278) • Diagnose abnormal engine noises or vibration concerns; determine necessary action. AST, MAST (p 278) Knowledge Objectives 1. Explain the basic principles of engine mechanical testing. (pp 262–264) 2. List the tools required for engine testing. (pp 262–264) 3. Describe the various types and causes of fluid leaks in engines. (pp 264–265) 4. List the factors involved in a cranking sound diagnosis. (p 267) 5. Explain how vacuum testing can be used to determine the engine’s general condition. (pp 268–269) 6. Describe a cylinder power balance test. (pp 270–271) 7. List the factors involved in cranking and running compression tests. (p 272) 8. Describe the principles of the cranking compression test. (p 272) 9. Describe the principles of the running compression test. (p 272) 10. Explain the factors involved in a cylinder leakage test. (p 276) 11. Describe the variety of noises and vibrations that a running engine creates. (p 278)

12. Describe how consumption of oil or coolant not located due to visual leaks may be determined by the color of the exhaust. (p 278) Skills Objectives 1. Perform a fluid leak inspection by looking under the hood. (pp 265–266) 2. Perform a fluid leak inspection by looking under the vehicle. (pp 266–267) 3. Perform a cranking sound diagnosis. (p 268) 4. Test engine vacuum using a vacuum gauge. (p 269) 5. Test engine vacuum using a pressure transducer and lab scope. (pp 269–270) 6. Perform a cylinder power balance test. (pp 271–272) 7. Perform a cranking compression test. (pp 272–274) 8. Perform a running compression test. (pp 274–275) 9. Perform a cylinder leakage test. (pp 276–278) Readings and Preparation Review all instructional materials, including Chapter 10 of Fundamentals of Automotive Technology: Principles and Practice and all related presentation support materials. Support Materials • Lecture PowerPoint presentation • Skill Drill PowerPoint presentations Direct students to visit the companion website to Fundamentals of Automotive Technology: Principles and Practice at www.cdxauto.com/CW/Fundamentals. Pre-Lecture You are the Automotive Technician “You are the Automotive Technician” is a progressive case study that encourages critical- thinking skills. Instructor Directions Direct students to read the “You are the Automotive Technician” scenario found at the beginning of Chapter 10. • You may wish to assign students to a partner or a group. Direct them to review the discussion questions at the end of the scenario and prepare a response to each question. Facilitate a class dialogue centered on the discussion questions. • You may also use this as an individual activity and ask students to turn in their comments on a separate piece of paper. Lecture I. Introduction

A. Mechanical condition of engine must be in good working order for engines to work properly and efficiently. 1. Engine mechanical testing is performed to diagnose major work needed. a. Understanding problems allows you to better advise customers on repairs. II. Engine Mechanical Testing A. Mechanical testing uses a series of tests to assess mechanical condition of engine. 1. Tests start off broad and narrow down as tests are performed. 2. Process helps identify location and cause of fault. B. Mechanical testing starts with good visual inspection. 1. Leaks a. Affirm ability of seals and gaskets to contain engine’s fluids. C. After visual inspection, take a deeper look at engine using tools and equipment. D. Variety of tools and equipment is available for fully assessing mechanical conditions. 1. Compression tester: used when suspicion of cylinder with low compression a. Measures amount of compression pressure generated 2. Vacuum gauge: measures amount of vacuum an engine can generate 3. Pressure transducer and lab scope: transducer measures engine vacuum or pressure and displays on lap scope a. Very accurate b. Used to determine mechanical issues with engine 4. Cylinder leakage tester: pumps air into cylinder and measures percentage of air leaking from the cylinder a. Leak is determined by looking, listening, or feeling. 5. Scan tool: communicates to vehicle’s computers through data link connector a. Displays readings from various sensors b. Retrieves trouble codes, freeze-frame data, and system monitor data c. Performs output tests such as cylinder power balance test d. Commands output devices to work 6. Stethoscope (standard and electronic): listens to unusual noises in vehicle III. Fluid Leaks A. Checking for fluid leaks is common and occurs during any routine maintenance. 1. Common to inspect vehicle for leaks when customer complains about fluid spots 2. Good practice to inspect engine assembly for leaks before performing any engine repairs

B. Color of leaking fluid can be clue as to the source. 1. Black fluid could be engine oil or gear lube. 2. Reddish-orange or green fluid could be anti-freeze. 3. Red fluid could be transmission or power steering fluid. C. Smell of fluid can also provide clues. 1. Fuel and brake fluid have very different scents. D. Gravity causes fluid to be pulled downward. 1. Always inspect all the way up to a place where there is no more fluid present. E. Several processes can be used to discover origin of leak. 1. Pressure wash or clean and reinspect for leaks. 2. Add a fluorescent dye to fluid. 3. Pressure test cooling system if coolant leak is suspected. F. Most leaks can be found via a thorough visual inspection. 1. Light and mirror 2. Top of the engine under the hood 3. Under the vehicle 4. Removing covers or heat shields G. Once leak is identified, start the engine and perform visual inspection again. 1. Be extremely careful around moving parts. H. If you cannot locate the leak visually, use fluorescent dye. 1. Once the dye has circulated, inspect engine assembly for leaks using recommended light for the dye you’re using. a. Special glasses might be required to enhance the fluorescent dye. IV. Cranking Sound Diagnosis Overview A. Engine noises can give valuable insight into the engine’s condition. 1. Cranking sound diagnosis can identify whether compression is the same across all cylinders. a. Compression is one of five critical requirements for cylinders to operate properly. 2. Disassemble engine before performing cranking sound diagnosis. 3. Noise could be from a misaligned starter, a spun crankshaft, a low-compression cylinder, or a no-compression condition that is due to bent valves caused by a broken timing belt. B. Engine will make rhythmic cranking sound if compression is same on all cylinders. 1. Train your ear to pick up different compression sounds. C. Vacuum gauges determine engine’s general condition.

1. Gauge shows difference between outside atmospheric pressure and amount of vacuum in engine. 2. Installed in vacuum in port on intake manifold 3. Reading for properly running engine is 17" to 21" of vacuum (57.6 to 71.1 kPa). 4. Technicians can view pressure traces to see how well cylinders are functioning. D. During engine vacuum test, all vacuum gauges are calibrated at sea level and all instructions and readings refer to sea level. 1. Must compensate when testing above sea level 2. Amount of vacuum an engine creates depends on piston rings, valves, ignition timing, and fuel. E. Using a pressure transducer and lab scope is similar to using a vacuum gauge. 1. More accurate 2. Can look at vacuum graphically V. Cylinder Power Balance Test Overview A. There are two purposes of a cylinder power balance test (also called power balance test). 1. Identifies which cylinders are not operating properly 2. Used as general indicator of each cylinder’s overall health a. The greater the difference in rpm drop, the greater the difference between each cylinder’s ability to produce its share of engine’s power. 3. Once problem is isolated, next step is to determine whether issue is mechanical and related to compression or ignition or a fuel-related issue. B. There are several ways to perform power balance test. 1. Knowing all options allows you to choose easiest method for your vehicle. a. Easiest is determined by PCM, ease of accessing required components, and tools available. 2. Determine whether to disable the ignition or fuel to each cylinder. a. Shutting down fuel is preferable if it is an option on the engine you’re working on. VI. Cranking and Running Compression Tests A. High-pressure hose is hand-threaded in spark plug hole of cylinder to be tested and then connected to compression gauge in a cranking or running compression test. 1. Engine needs to be cranked over or started, depending on test. a. Should crank at least five compression pulses to get accurate reading 2. Compression gauge reads amount of pressure piston is producing. a. Compresses air in cylinder

B. Cranking compression test is performed when indications show misfiring or dead cylinder not caused by ignition or fuel problem. 1. Measures air pressure as it is compressed in cylinder 2. Cylinders should all measure within 10% to 15% of each other. C. For compression test to be accurate, engine should be at operating temperature, spark plugs removed, battery fully charged, throttle held wide open, and at least five compression pulses made on each cylinder. 1. Conditions will help engine create maximum compression and accurate readings. D. In a running compression test, engine is running during compression test. 1. Checks engine’s ability to move air into and out of cylinder a. Engine’s ability to breathe 2. Test performed in two parts: idle and snap throttle 3. Idle: engine running, throttle relatively closed, compression pressure will be about half of cranking compression pressure 4. Snap throttle: engine idling, throttle snapped open and then closed quickly a. Idea is not to make rpm change. 5. Test is performed by leaving all spark plugs in engine except for one in cylinder being tested. 6. Compression tester Schrader valves use lighter-weight springs than tire Schrader valves. a. Not interchangeable VII. Cylinder Leakage Test Overview A. Cylinder leakage test is performed on a cylinder with low compression to determine severity of compression leak and leak’s location. 1. Compressed air is applied to cylinder through tester calibrated to show amount of leakage. a. Ideal reading is 0%. b. Manufacturers consider up to 20% acceptable. 2. Small leakage past piston rings is okay; any leakage past one of the valves or the head gasket is not okay. a. Likely major mechanical engine issue if leakage 3. Point of test is to measure how much air is leaking as well as to determine from where. B. There are several critical steps needed to make sure cylinder leakage tests are accurate. 1. Engine should be near operating temperature. a. Ensures oil has been circulated to piston rings to help seal them 2. Loosen each spark plug about one turn. 3. Run engine at 1500 rpm for 10 to 15 seconds.

a. Helps blow out any chunks of carbon that were straddling the spark plug 4. Cylinder leakage is measured when piston is on top dead center on compression stroke. 5. You’ll have to turn crankshaft to position each piston before pressurizing system. a. Hardest part is getting pistons exactly on top dead center. i. Screw cylinder leakage tester into spark plug hole and slowly turn engine over by hand. ii. Use a plastic straw that fits down spark plug hole that can be pushed up by piston without damaging cylinder or piston. VIII. Diagnosing Engine Noise and Vibrations A. Running engines are relatively quiet. 1. Noises can indicate small issues as well as something majorly wrong. 2. Investigate unusual noises and build on your experience. B. Using a mechanic’s stethoscope can help locate engine noise. 1. Can be mechanical or electronic a. Mechanical is most common. b. Electronic has settings that enhance selected sound frequencies. C. Vibrations can be difficult to pinpoint and can come from engine or drive train. 1. Best clue is to determine if vibration occurs with engine running irrespective of vehicle movement. X. Diagnosing Oil Consumption, Coolant Consumption, and Exhaust Color A. Coolant should not have consumption if cooling system is working properly. B. Engine oil can have small amount of consumption and be considered normal. C. Consumption of oil or coolant that cannot be located with visual inspection could be diagnosed by color of exhaust. 1. Bluish tint: engine oil burning 2. Blue is constant while engine running: rings not sealing due to worn rings or cylinder walls 3. Blue present only when start engine: likely a valve steam seal or valve guide issue 4. Black: excessively rich fuel mixture 5. White after engine is warmed up: coolant leaking into exhaust a. Blown head gasket b. Blown intake gasket c. Cracked cylinder head d. Leaky exhaust gas recirculation cooler on some vehicles

XI. Summary A. Appropriate service information is needed to make an accurate diagnosis. B. The best source for vehicle service information is the vehicle manufacturer. C. Major vehicle components often have identification numbers. D. A systematic mechanical testing and verification process is needed to diagnose and repair an engine problem. E. Engine mechanical testing tools include: a compression gauge, vacuum gauge, cylinder leakage tester, and scan tool. F. The color of a leaking fluid can assist in identifying the source of a leak. G. During engine cranking, the engine will make an even cranking sound if the compression is even between the cylinders. H. A vacuum gauge is used to determine the general condition of an engine. I. A cylinder power balance test is used to determine whether all of the engine cylinders are working properly. J. A cranking compression test measures the compressed air pressure in the cylinder. K. A running compression test checks the engine’s breathing ability. L. A cylinder leakage test is performed on a cylinder with low compression. M. A stethoscope can be used to isolate an engine noise. N. Exhaust smoke can indicate the source of an engine problem. O. An odor can help diagnose an engine problem. P. Engine tests must be properly interpreted to correct an engine problem. Post-Lecture This section contains various student-centered end-of-chapter activities designed as enhancements to the instructor’s presentation. As time permits, these activities may be presented in class. They are also designed to be used as homework activities. ASE-Type Questions This activity is designed to assist the student in gaining a further understanding of and familiarity with ASE-type questions. Instructor Directions 1. Direct students to read and individually answer the “ASE-Type Questions” located in the Wrap-up section at the end of Chapter 10. Allow approximately 10 minutes for this part of the activity.

2. Facilitate a class review and dialogue of the answers, allowing students to correct responses as may be needed. Use the quiz question answers noted below to assist in building this review. 3. You may wish to ask students to complete the activity on their own and turn in their answers on a separate piece of paper. Answers to ASE-Type Questions 1. Tech A says that a cranking sound diagnosis can be used to diagnose problems in the ignition system. Tech B says that a cranking sound diagnosis can indicate differences in compression. Who is correct? a. Tech A b. Tech B c. Both A and B d. Neither A nor B Answer: b

2. Tech A says that a power balance test is a good way to narrow a misfire down to a particular cylinder or cylinders. Tech B says that a cylinder power balance test measures the volumetric efficiency of the cylinder being tested. Who is correct? a. Tech A b. Tech B c. Both A and B d. Neither A nor B Answer: a

3. Tech A says that a cranking compression wet test can indicate if the cylinder has worn piston rings. Tech B says that the throttle should be held wide open during a cranking compression check. Who is correct? a. Tech A b. Tech B c. Both A and B d. Neither A nor B Answer: c

4. Tech A says that low compression on a single cylinder will cause an engine not to start. Tech B says that low compression on a single cylinder will affect the engine’s cranking sound. Who is correct? a. Tech A b. Tech B

c. Both A and B d. Neither A nor B Answer: b

5. Tech A says that a cylinder leakage test is performed on a cylinder with low compression to determine the severity of the leak and where it is located. Tech B says that manufacturers will consider up to 50% cylinder leakage past the piston rings acceptable. Who is correct? a. Tech A b. Tech B c. Both A and B d. Neither A nor B Answer: a

6. Tech A says that a scan tool connected to the data link connector (DLC) will perform a cylinder power balance test and report cylinder pressures. Tech B says that a scan tool will perform a cylinder power balance test and report whether the rings or valves have failed. Who is correct? a. Tech A b. Tech B c. Both A and B d. Neither A nor B Answer: d

7. Tech A says that researching related service information for a vehicle repair will assist the technician. Tech B says that research should be done only when the technician needs direction. Who is correct? a. Tech A b. Tech B c. Both A and B d. Neither A nor B Answer: a

8. Tech A says that a vacuum gauge needle that dips 4–8 inches rhythmically can indicate a burned valve. Tech B says that a stethoscope can be used to determine the source of unusual engine noises. Who is correct? a. Tech A

b. Tech B c. Both A and B d. Neither A nor B Answer: c

9. Tech A says that a vacuum test can determine exhaust restriction. Tech B says that when performing a cylinder power balance test, results should be 5% or less. Who is correct? a. Tech A b. Tech B c. Both A and B d. Neither A nor B Answer: a

10. Tech A says that a bad cam lobe or broken valve spring will show up during a running compression test. Tech B says that when performing a cylinder leakage test, the engine must be running to get proper results. Who is correct? a. Tech A b. Tech B c. Both A and B d. Neither A nor B Answer: a

Assignments A. Review all materials from this lesson and be prepared for a lesson quiz to be administered (date to be determined by instructor). B. Direct students to read the next chapter in Fundamentals of Automotive Technology: Principles and Practice as listed on your syllabus to prepare for the next class session.