ASE A1 (Engine Repair) Practice Test – Cumulative Already Passed

an engine miss is being diagnosed using a cylinder leakage test. Technician A says that any cylinder with over 20% leakage has excessive leakage. Tech B says that air leaking from the tailpipe indicates a cracked cylinder. A only, B only, A & B, Neither . A only: If cylinder leakage exceeds 20%, check for air escaping the tailpipe, the PCV valve opening in the rocker arm cover, and the top of the throttle body or carburetor. Air leaking from the tailpipe usually indicates an exhaust valve leak during a compression test, a cylinder has 40% of the specified compression reading. When the tech performs a wet test, the compression reading on this cylinder has 75% of the specified reading. The cause of the low compression reading could beworn piston rings, a burned exhaust valve, a bent intake valve, a worn camshaft lobe, worn piston rings if compression increases during a wet test, this indicates worn piston rings. Compression would not increase if an exhaust valve is burned, intake valve is bent, or camshaft lobe is worn. the customer complains that the engine cranks but does not start; the first thing to check should be valve train operation, battery voltage, compression, engine vacuum, valve train operation:if the engine cranks properly, the battery is not the problem. Compression would not be the FIRST test, and because engine vacuum is low during a crank, a vacuum test would not be conclusive. during a cylinder balance test on an engine with fuel injection, one cylinder provides very little rpm drop. Tech A says the ignition system may be misfiring on that cylinder. Tech B says the engine may have an intake manifold vacuum leak. A only, B only, A & B, Neither , Both A&B Both a misfiring ignition system and an intake manifold leak could cause a cylinder to contribute too little power while discussing basic diagnostic procedures,Tech A says the most complicated diagnostic tests should be performed first. Tech B says that you should first question the customer to obtain as much info as possible about the problem A, B , A & B, Neither, B Always attempt the more simple diagnosis first with the engine idling, a vacuum gauge connected to the intake manifold fluctuates (from 15 to 20). These fluctuations may be caused by late ignition timing, intake manifold vacuum leaks, a restricted exhaust system, sticky valve stems and guides, sticky valve stems and guides