© Goodheart-Willcox Co., Inc.

Engine Problem Diagnosis and Tune-Up Chapter 19 Engine Problem Diagnosis and Tune-Up © Goodheart-Willcox Co., Inc.

Objectives Describe a minor tune-up and a major tune-up. List tune-up safety rules. List items to look for in a preliminary inspection. Perform a current starter draw test. © Goodheart-Willcox Co., Inc.

Objectives Perform dry and wet compression tests and analyze the results. Perform a cylinder leakage test and analyze the results. Perform a vacuum test and analyze the results. © Goodheart-Willcox Co., Inc.

Objectives Perform a cylinder balance test and analyze the results. Describe valve adjustment. List general tune-up rules. © Goodheart-Willcox Co., Inc.

What Is a Tune-Up? Engine tune-up returns engine to peak performance after part wear and deterioration Tune-up involves Replacing worn parts Performing basic service tasks Making adjustments © Goodheart-Willcox Co., Inc.

Minor Tune-Up Minor tune-up is preventative maintenance Performed when engine is in good condition Engine has little or no wear © Goodheart-Willcox Co., Inc.

Minor Tune-Up (Cont.) Visually inspect for problems Listen for abnormal noises Check condition of engine oil and coolant © Goodheart-Willcox Co., Inc.

Minor Tune-Up (Cont.) Check for trouble codes in computer Replace distributor cap, rotor, and spark plugs (older, high-mileage vehicles) Check and adjust ignition timing Replace air and fuel filters Make fuel system adjustments where applicable © Goodheart-Willcox Co., Inc.

Minor Tune-Up (Cont.) Clean throttle body, idle air bypass, and EGR system Test and service emission control system Fill all fluid reservoirs to correct level Road test the vehicle © Goodheart-Willcox Co., Inc.

Major Tune-Up Major tune-up is done when systems or engine is in poor condition and includes All parts of minor tune-up Diagnostic tests to determine what should be done to bring vehicle back to good operating condition © Goodheart-Willcox Co., Inc.

Tune-Up Safety Engage emergency brake and block wheels when engine is to be running Place exhaust hose over tailpipe when running engine in enclosed shop Keep clothing, hands, tools, and equipment away from moving parts Disconnect battery when recommended Be careful not to touch hot exhaust manifold © Goodheart-Willcox Co., Inc.

Tune-Up Safety (Cont.) Keep test equipment leads away from exhaust manifolds, fan, and belts Wear eye protection when blowing debris from parts or when working near engine fan Keep fire extinguisher handy, especially during fuel system tests and repairs With diesel engine, disable injection pump when removing injection line © Goodheart-Willcox Co., Inc.

Preliminary Inspection Look for problems with Battery Air cleaner Fuel system Belts and hoses Poor electrical connections Fix problems before proceeding with tune-up © Goodheart-Willcox Co., Inc.

Evaluating the Engine and Its Systems If scan tool indicates problem with oxygen sensor, remove and inspect sensor Note color of tip of oxygen sensor Color can indicate condition of engine and support systems © Goodheart-Willcox Co., Inc.

Evaluating the Engine and Its Systems (Cont.) (Tomco, Inc.) © Goodheart-Willcox Co., Inc.

Evaluating the Engine and Its Systems (Cont.) If engine is running too hot or cold, measure operating temperature Use engine analyzer or handheld tester to check for blown head gasket To find hard-to-locate oil and coolant leaks, add dye and use a black light © Goodheart-Willcox Co., Inc.

Cranking Balance Test Cranking balance test finds cylinders with low compression Monitors current drawn by starter motor during complete turn of crankshaft Low current draw indicates that starter is not being loaded enough by compression stroke © Goodheart-Willcox Co., Inc.

Compression Test Compression test determines engine’s mechanical condition Low compression may be caused by Burned valve or valve seat Physical engine damage Blown head gasket Worn rings or cylinders Valve train troubles Jumped timing chain or belt © Goodheart-Willcox Co., Inc.

Compression Test—Gasoline Engine Remove all spark plugs Block open throttle plates Disable ignition system Disable fuel injection system Screw compression gauge into spark plug hole Crank engine and let it rotate for about six compression strokes © Goodheart-Willcox Co., Inc.

Compression Test—Gasoline Engine (Cont.) Write down readings for each cylinder Compare readings to specifications (Snap-on Tool Corp.) © Goodheart-Willcox Co., Inc.

Compression Test—Diesel Engine Procedure is similar to compression test for gasoline engine Do not use compression gauge intended for gasoline engine on diesel engine Diesel compression gauge must read up to 600 psi (4200 kPa) © Goodheart-Willcox Co., Inc.

Compression Test Results Gasoline engine readings should be 125-175 psi (860-1200 kPa) in each cylinder Diesel engine readings should be 275-400 psi (1900-2750 kPa) © Goodheart-Willcox Co., Inc.

Compression Test Results (Cont.) Look for cylinder pressure variations during compression check © Goodheart-Willcox Co., Inc.

Wet Compression Test Wet compression test should be done on any cylinder with compression reading below specifications © Goodheart-Willcox Co., Inc.

Wet Compression Test (Cont.) © Goodheart-Willcox Co., Inc.

Cylinder Leakage Test Cylinder leakage test measures air leakage out of engine combustion chamber © Goodheart-Willcox Co., Inc.

Vacuum Test Vacuum test measures intake manifold vacuum (General Motors) © Goodheart-Willcox Co., Inc.

Cylinder Balance Test Cylinder balance test disables spark plug in one cylinder at a time Tests whether cylinders are firing properly © Goodheart-Willcox Co., Inc.

Valve Adjustment On some engines, valve adjustment involves turning rocker arm adjusting screws (Volvo) © Goodheart-Willcox Co., Inc.

Valve Adjustment (Cont.) On some OHC engines, valve adjustment involves changing shim thickness to alter valve lash (Ford) © Goodheart-Willcox Co., Inc.

Tune-Up Parts Replacement Depending on age and condition of engine, parts may need replacement during tune-up On newer vehicles, only spark plugs and filters may need replacement Older vehicles with high mileage may need multiple parts © Goodheart-Willcox Co., Inc.

Tune-Up Parts Replacement (Cont.) Parts that may need replacing include Spark plugs Spark plug wires Distributor parts Fuel system parts Emission control parts © Goodheart-Willcox Co., Inc.

Tune-Up Adjustments Adjustments needed will vary with make, model, and condition of vehicle Most common adjustments include Spark plug gap Pickup coil air gap Ignition timing or injection timing Idle speed © Goodheart-Willcox Co., Inc.

Tune-Up Adjustments (Cont.) (Snap-on Tool Corp.) © Goodheart-Willcox Co., Inc.

General Tune-Up Rules Gather information about performance of engine Use professional, high-quality tools and equipment Make sure engine has warmed to full operating temperature Refer to service information or emission sticker for specifications and procedures © Goodheart-Willcox Co., Inc.

General Tune-Up Rules (Cont.) Use quality parts Keep service records Complete basic maintenance service Inform customer about tune-up intervals Road test the vehicle when tune-up is complete © Goodheart-Willcox Co., Inc.

Diesel Engine Tune-Up (Maintenance) Diesel maintenance involves Replacing air filter element Cleaning, draining, or replacing fuel filters Adjusting engine idle speed and throttle cable Inspecting engine and related systems Checking injection timing Changing engine oil and oil filter Servicing emission control systems periodically © Goodheart-Willcox Co., Inc.

Review Questions A major tune-up consists of a minor tune-up plus which of the following? Oil change Coolant change Battery recharge Diagnostic tests Answer: D. Diagnostic tests © Goodheart-Willcox Co., Inc.

Review Questions When working on a diesel engine, disable the ____. Answer: injection pump © Goodheart-Willcox Co., Inc.

Review Questions True or False? Checking for fuel system leaks is part of the preliminary inspection. Answer: True © Goodheart-Willcox Co., Inc.

Review Questions A cranking balance test will locate cylinders with ____ compression. Answer: low © Goodheart-Willcox Co., Inc.

Review Questions True or False? A wet compression test is used to locate defective valves. Answer: False. A wet compression test is used to locate defective rings. © Goodheart-Willcox Co., Inc.

Review Questions In a(n) ____ test, shop air is pumped into a cylinder and a pressure gauge is used to measure air leakage. Answer: cylinder leakage © Goodheart-Willcox Co., Inc.

Review Questions What would cause a vacuum gauge to show higher than normal readings while idling in neutral? Burned exhaust valve Burned intake valve Worn oil rings None of the above. Answer: D. None of the above. © Goodheart-Willcox Co., Inc.

Review Questions What test is commonly performed to find out if individual cylinders are firing properly? Answer: Cylinder balance test © Goodheart-Willcox Co., Inc.

Review Questions In some ____ engines, valves must be adjusted by changing the shim thickness. Answer: OHC © Goodheart-Willcox Co., Inc.

Review Questions True or False? Diesel engines should be tuned up at regular intervals, just like gasoline engines. Answer: False. Diesel engines do not require periodic tune-ups. © Goodheart-Willcox Co., Inc.

Glossary Compression test Cranking balance test Test used to determine compression stroke pressure. It should be done anytime symptoms point to cylinder pressure leakage. Cranking balance test Test performed by an engine analyzer to find cylinders with low compression due to a burned valve, worn piston rings, or other problems. © Goodheart-Willcox Co., Inc.

Glossary Cylinder balance test Cylinder leakage test Measures the power output from each of the engine’s cylinders. Cylinder leakage test Measures air leakage out of the engine combustion chamber to find mechanical problems. Cylinder pressure variations Some cylinders have normal pressure and some have low readings, causing rough idle and lack of power © Goodheart-Willcox Co., Inc.

Glossary Diesel maintenance Engine tune-up A diesel engine tune-up. A maintenance operation that returns the engine to peak performance after part wear and deterioration. It involves the replacement of worn parts, basic service tasks, making adjustments, and, sometimes, minor repairs. © Goodheart-Willcox Co., Inc.

Glossary Major tune-up Minor tune-up Includes the steps for a minor tune-up plus diagnostic tests such as scope analysis, compression tests, or vacuum tests. Minor tune-up Preventative maintenance done when the engine is in good operating condition. © Goodheart-Willcox Co., Inc.

Glossary Vacuum test Wet compression test Using a vacuum gauge to measure intake manifold vacuum and indicate engine condition. Wet compression test Compression test in which a small amount of oil is placed in the cylinder to determine if bad rings are causing low compression. © Goodheart-Willcox Co., Inc.