ASE A1 Certification Practice Test

26.

Answer A is wrong. Camshaft duration, lift, and overlap are vital to valve timing and engine performance. Camshaft duration refers to time; it affects the valve's opening and closing and how long it stays open. It's measured in degrees of crankshaft rotation.

Answer B is correct. As the engine cycles, there's a time when the intake and exhaust valves remain open simultaneously (valve overlap). Valve overlap is an essential function in valve timing.

Answer C is wrong. The exhaust gases flowing through the exhaust valve and manifold help draw the fresh air-fuel charge through the intake valve and into the combustion chamber. This timing is known as valve overlap.

Answer D is wrong. Measure from the nose to the heel of the cam lobe with an outside micrometer, then deduct the base circle. This results in an accurate measurement of the cam lobe lift.

27.

Answer A is wrong. A gauge that reads a steady low (15 "hg - 20 "hg) indicates late valve or ignition timing, leaking manifold gasket, low compression, leaking carburetor, or a stuck throttle valve.

Answer B is wrong. A gauge that reads steady (17 "hg - 22 "hg) indicates a normal running engine.

Answer C is correct. A gauge that fluctuates between (15 "hg and 20 "hg) indicates a stuck valve or engine misfire.

Answer D is wrong. A gauge needle that drops slowly at idle indicates a clogged or blocked exhaust.

28.

Answer A is correct. If this reading is too much and the gap is too large, replace the damaged piston. The top ring takes the most compression. It causes the ring to slap against and wear the lands in the piston groove.

Answer B is wrong. Installing a larger piston ring would not repair this condition.

Answer C is wrong. Remove carbon from the ring grooves before taking measurements.

Answer D is wrong. Many manufacturers install tapered rings on their pistons. They must be installed in the groove correctly, typically with the dot facing up. Check with the manufacturer's specifications before installing piston rings.

29.

Answer A is wrong. A vacuum leak results in a lean air-fuel ratio.

Answer B is wrong. A leaking head gasket can leak coolant from the coolant jacket into the combustion chamber. The vehicle would likely emit white-colored exhaust from its tailpipe.

Answer C is wrong. Worn piston rings allow oil to bypass the seal and burn in the cylinder. Oil burning in the combustion chamber results in blue-gray exhaust from the tailpipe.

Answer D is correct. A rich air-fuel ratio produces black-colored exhaust, soot, and a sulfur odor at the vehicle's tailpipe.

30.

Answer A is wrong. A specific gravity test determines the weight of a certain volume of liquid divided by an equal amount of water. A fully charged automotive battery has a specific gravity of 1.265.

Answer B is wrong. The discharge rate is one-half of the battery's cold-cranking rating. Apply this load to the battery for 15 seconds. The battery's voltage must remain above 9.6 volts at 70° F.

Answer C is correct. Both technicians are correct.

Answer D is wrong. The specific gravity of a battery is a good indication of its state of charge. Use a hydrometer and adjust to temperature by adding .004 for every ten degrees above 80° F and subtracting .004 for every 10° below 80° F.