ASE Diesel Practice Test QUESTIONS AND ANSWERS ALL CORRECT

ASE Diesel Practice Test When a diesel engine is operated under a load, coolant continually comes out of the radiator overflow and there are bubbles in the radiator. Which of these is the most likely cause? (A) Too much coolant in the cooling system (B) A clogged radiator (C) A stuck-open thermostat (D) Compression leakage into the cooling system Correct Answer: D A diesel engine has excessive black smoke when started in the morning. Which of these could be the cause? (A) A bad fuel injection nozzle (B) A restricted fuel filter (C) A blocked fuel tank vent (D) A leaking fuel return line Correct Answer: A Which of these can cause a no-start condition on a HEUI engine? (A) High fuel pressure (B) Low injection control pressure (C) High boost pressure (D) Low boost pressure Correct Answer: B A diesel engine is hard to start, but runs good after it has been primed and run for a few minutes. The most likely cause is a: (A) leaking injector line. (B) leaking fuel return line. (C) plugged fuel tank vent. (D) bad transfer pump check valve. Correct Answer: D A diesel engine with wet liners has been running too hot, and there is coolant in the crankcase. The most likely cause is: (A) a cracked block. (B) cracked liners. (C) leaking liner seals. (D) a leaking injector seal. Correct Answer: C Diesel engine cylinder liner protrusion (height) can be adjusted by selecting the correct size: (A) cylinder liner. (B) head gasket. (C) liner shim. (D) fire ring. Correct Answer: C An electronically-controlled diesel engine will not start. Any of these could be the cause EXCEPT a failed: (A) camshaft position sensor. (B) engine control module (ECM). (C) ECM ground circuit. (D) throttle position sensor (TPS). Correct Answer: D The cause of a logged fault code in an electronic diesel engine has just been repaired. Technician A says that the codes should be cleared before releasing the vehicle. Technician B says that the customer's password should be reset before releasing the vehicle. Who is right? (A) A only (C) Both A and B (B) B only (D) Neither A nor B Correct Answer: A A diesel engine has low power and low turbocharger boost pressure is found. Technician A says that a leaking exhaust manifold could be the cause. Technician B says that a plugged turbocharger oil return line could be the cause. Who is right? (A) A only (B) B only (C) Both A and B (D) Neither A nor B Correct Answer: A The parking brakes fail to apply on a truck with air brakes. Technician A says that low air pressure in the spring brake chamber could be the cause. Technician B says that a ruptured spring brake diaphragm could be the cause. Who is right? (A) A only (B) B only (C) Both A and B (D) Neither A nor B Correct Answer: D A truck equipped with air brakes has an uneven braking problem. Which of these could be the cause? (A) A binding treadle (foot) valve (B) Low brake line air pressure (C) A bad brake drum (D) A bad governor Correct Answer: C A service brake on a truck with an air brake system releases too slowly. Technician A says that low air pressure could be the cause. Technician B says that a kinked air line could be the cause. Who is right? (A) A only (C) Both A and B (B) B only (D) Neither A nor B Correct Answer: B A service brake chamber leaks when the brakes are applied. Which of these could be the cause? (A) Excessive push rod travel (B) A bad chamber diaphragm (C) A broken chamber return spring (D) A misaligned push rod Correct Answer: B All the wheels on a truck with air brakes lock up when a small amount of pressure is applied to the treadle (foot) valve. Which of these could be the cause? (A) The application valve is bad. (B) The limiting valve is leaking. (C) The compressor regulator is set too high. (D) The brakes are adjusted too high. Correct Answer: A When an air reservoir tank is drained, there is an excessive amount of moisture. This could be caused by a: (A) cracked air compressor bracket. (B) clogged air compressor intake. (C) failed one way check valve. (D) failed air dryer purge valve. Correct Answer: D All the brakes drag on a truck with hydraulic brakes. Which of these could be the cause? (A) Air in the hydraulic system (B) Too high vacuum supply to the power brake booster (C) A leaking secondary cup in the master cylinder (D) No brake pedal free travel Correct Answer: D A truck with hydraulic brakes pulls to one side when the brakes are applied. Any of these could be the cause EXCEPT a: (A) sticking wheel cylinder piston. (B) grease contaminated brake lining. (C) crimped hydraulic line. (D) plugged compensating port. Correct Answer: D The driver of a truck with air brakes says it has poor stopping power. Any of these could be the cause EXCEPT: (A) the quick release valve exhaust port is plugged. (B) the air pressure is too low. (C) the application line is restricted. (D) the brakes are out of adjustment Correct Answer: A Which of these could cause the front tires of a truck to show a feathered edge wear pattern? (A) An incorrect toe setting (B) An incorrect camber setting (C) An incorrect caster setting (D) Incorrect tire pressures Correct Answer: A The drive axles on a truck with a walking beam suspension are out of alignment. Technician A says that incorrect length torque rods could be the cause. Technician B says that worn walking beam bushings could be the cause. Who is right? (A) A only (C) Both A and B (B) B only (D) Neither A nor B Correct Answer: B The driver of a truck that has just had its front springs and hangers replaced says that it is hard to keep in a straight ahead position. Technician A says that this could be caused by installing the caster shims backwards. Technician B says that this could be caused by installing forward spring hangers which are too short. Who is right? (A) A only (C) Both A and B (B) B only (D) Neither A nor B Correct Answer: A The driver of a truck says that it is hard to steer and the steering wheel return is poor. Technician A says that binding kingpins could be the cause. Technician B says that too much toe-in could be the cause. Who is right? (A) A only (C) Both A and B (B) B only (D) Neither A nor B Correct Answer: A Rust streaks coming from around the stud holes of a disc wheel could be caused by: (A) an overloaded conditon. (B) overtorqued lug/cap nuts. (C) an out-of-balance condition. (D) loose lug/cap nuts. Correct Answer: D A truck has a history of springs breaking at the center bolt holes. Technician A says that loose U-bolts could be the cause. Technician B says that loose spring shackles could be the cause. Who is right? (A) A only (C) Both A and B (B) B only (D) Neither A nor B Correct Answer: A A constant buzzing noise is coming from the power steering pump. Technician A says air in the system could be the cause. Technician B says that a stuck-open relief valve could be the cause. Who is right? (A) A only (C) Both A and B (B) B only (D) Neither A nor B Correct Answer: A The tandem rear axle air suspension ride height rises above normal as the vehicle is unloaded. Which of these could be the cause? (A) A kinked air spring (bag) supply line (B) A leaking height control valve (C) A plugged height control valve exhaust port (D) A leaking pressure protection valve Correct Answer: C All of these should be checked before aligning the front wheels on a truck EXCEPT: (A) tire pressure. (B) ride height. (C) wheel bearing adjustment. (D) tire balance. Correct Answer: D In the charging system shown, the meter reading will show: (A) charging output voltage. (B) regulator operating voltage. (C) charging circuit voltage drop. (D) ignition switch voltage drop. Correct Answer: C A truck's cab heater blower motor operates at low speed only. Which of these is the most likely cause? (A) An open blower switch ground (B) A bad blower switch (C) A binding blower cage (D) A short to power at the blower motor Correct Answer: B The horns in the circuit shown only blow when a jumper wire is connected between terminals 30 and 87 of the horn relay. Technician A says that a failed horn relay could be the cause. Technician B says that a short to ground in the circuit between the horn relay and the horn button could be the cause. Who is right? (A) A only (C) Both A and B (B) B only (D) Neither A nor B Correct Answer: A Any of these may cause low alternator output EXCEPT: A) a loose alternator output terminal. (B) a slipping alternator belt. (C) shorted-to-ground stators. (D) high resistance at the alternator ground. Correct Answer: C A driver complains that the trailer marker lights are dim at night while braking. Which of these is the most likely cause? (A) Low battery voltage (B) One burned out brake light bulb (C) A poor ground in the trailer light cord (D) Too much grease on the 5th wheel Correct Answer: C Both headlights on a vehicle are dim in high beam and normal in low beam. Technician A says that a poor headlight ground could be the cause. Technician B says that a shorted headlight switch could be the cause. Who is right? (A) A only (C) Both A and B (B) B only (D) Neither A nor B Correct Answer: D The voltage readings shown were taken while cranking the engine. Which of these is indicated by the readings? (A) Battery #2 has resistance in the ground cable. (B) Battery # 2 is weaker than battery #1. (C) Battery #1 is low on electrolyte. (D) Battery #2 should be replaced. Correct Answer: B Which of these is the minimum tire tread depth permitted by federal DOT standards on all steer axle tires on trucks, tractors, or buses? (A) 1/32 in. (B) 2/32 in. (C) 4/32 in. (D) 5/32 in. Correct Answer: C Technician A says that the low air brake pressure warning lamp should be lit when the supply system pressure is below 60 psi. Technician B says that the parking brakes should automatically apply when the supply system air pressure falls below 45 psi. Who is right? (A) A only (C) Both A and B (B) B only (D) Neither A nor B Correct Answer: C The driver of a tractor/trailer reports that the engine's fan hits the shroud when accelerating under a load. The most likely cause is: (A) overspeeding the engine. (B) improper vehicle shifting. (C) excessive fan blade flexing. (D) a broken engine mount. Correct Answer: D A drive axle lubricant is a milky color. The most likely cause is: (A) metal contamination. (B) mixing lubricant types. (C) gasket sealer contamination. (D) water contamination. Correct Answer: D The PM inspector notices that part "X" in the illustration is missing. This could cause: (A) fluid contamination. (B) loss of static pressure. (C) excessive pedal effort. (D) brake warning lamp illumination. Correct Answer: A When pressure testing a cooling system, the technician should apply: (A) 5 pounds of pressure with the engine running. (B) the amount of pressure listed on the radiator cap. (C) pressure not to exceed the danger zone on the pressure gauge. (D) 5 pounds more pressure than listed on the radiator cap. Correct Answer: B When performing a battery load test on a multiple battery vehicle: (A) connect the load test clamps to any positive battery post and ground. (B) disconnect the ground cable(s) from the frame. (C) connect the load test amps clamp around a negative vehicle battery cable. (D) isolate the batteries from each other. Correct Answer: D A zero reading on an air restriction dash gauge could be caused by any of these EXCEPT: (A) a bad restriction gauge. (B) a plugged air filter. (C) an opening in the intake system. (D) a torn air filter. Correct Answ