chapter 28 truck brake systems exam questions and answers

In what year was FMVSS-121 introduced? A. 1997, B. 1998, C. 1975, or D. 1957? 1975 When a truck has no air pressure in its tanks, which warning devices are activated when the ignition key is turned on? A. A buzzer, B. Red light, C. A dash gauge, or D. All of the above. all of the above what legislation mandates every required standard of a highway truck air brake system A. osha B. fmvss 105 C. fmvss 121 D. nhtsa C. FMVSS 121 if a truck is FMVSS 121 compliant, which of the following air reservoirs must be incorporated into the air brake circuit A. wet taknk and purge tanks B. front brake and rear brake tanks C. supply, primary, and secondary tanks D. wet tank, supply tank, and air start tanks C. supply, primary, and secondary tanks when the emergency/parking brakes are released on an air-brake equipped highway tractor-trailer combination with a three valve system, which dash control button(s) must be depressed before you can move the rig A. system park only B. trailer supply C. tractor park D. all of the above D. all of the above which of the following are function(s) of slack adjusters used on truck air brake systems A. multiple force applied to the s-cam B. define shoe to drum freeplay C. convert linear force to rotational force D. all of the above all of the above which types of foundation brakes are used on air-brake equipped trucks and trailers A. s-cam actuated B. air disc brakes C. air wedge-actuated D. all of the above all of the above in a truck air brake system which sub-circuit is primarily responsible for actuating front axle service brakes when the system is functioning normally A. primary circuit B. secondary circuit C. supply circuit D. wet circuit B. secondary circuit in a typical FMVSS 121 compliant tractor-trailer when you actuate the trailer hand control valve which circuit supplies air to the trailer service brakes when the system is functioning normally A. primary circuit B. secondary circuit C. supply circuit D. park/emergency circuit B. secondary circuit when a FMVSS 121 compliant tractor combination for governor cut-in pressures A. cut-out at 135 psi and cut-in at 115 psi B. cut-out at 135 psi and cut in at 90 psi C. cut out at 110 psi and cut in at 80 psi D. cut-out at 115 psi and cut in at 85 psi A. cut-out at 135 psi and cut-in at 115 When a FMVSS-121 compliant tractor-trailer combination is moving down the highway at speed of 50 mph, which of the following circuits must be charged with air? A. Service brake circuit B. Primary circuit C. Secondary circuit D. Hold-off circuit D. hold off circuit Which of the following service application valves is sometimes referred to by a truck driver as a trolley valve or spike? A. Trailer Hand Valve B. Trailer Supply Valve C. Foot Valve D. Treadle Valve A. trailer hand valve Which of the following best describes the function of a tractor protection valve? A. Pressure protects the tractor air supply in the event of loss of pressure in trailer. B. Routes trailer supply and service application signal to the trailer pneumatic circuits. C. Blocks service signal air to the trailer until trailer air supply is activated. or D. All of the above. D. all of the above When a FMVSS-121 compliant tractor-trailer is running down a highway and the driver applies the service brakes, which of the following is true at the time of the brake application? A. Only the service application circuit is charged with air. B. Only the hold-off circuit is charged with air. C. Both service application and hold-off circuits are charged with air. D. Hold-off circuit is exhausted and service application circuit is charged with air. C. Both service application and hold-off circuits are charged with air If you have to make an adjustment to the air system cutout pressure, where should the adjustment be made? A. Governor B. Unloader Valve C. Dryer Purge Valve D. Pressure Protection Valve governor An airbrake-equipped highway tractor features a single-dash air pressure gauge with two needles, one green and the other red. What does the red needle display? A. Service brake application pressure. B. Primary circuit pressure. C. Secondary circuit pressure. D. Hold-off pressure. C. Secondary circuit pressure What is the primary function of a relay valve? A. Remote-controlled service brake valve B. Relays pressure from the primary circuit to the secondary circuit C. Relays governor signal pressure to the unloader pistons D. Routes hold-off air to the hold-off chambers Remote-controlled service brake valve How is the relay secondary section of the FMVSS-121 compliant dual circuit foot valve actuated when the air brake circuit is functioning properly? A. Pneumatically B. Mechanically C. Both mechanically and pneumatically D. By foot pressure alone Pneumatically