Shop pop quiz: commonly missed issues

The following questions cover commonly missed issues in school bus maintenance. For the budget-minded director or fleet manager, making sure that technicians get these types of items right the first time is important in keeping costs down.

A commonly overlooked problem that can cause excessive tire wear and cost to your budget.

1. The driver of a school bus that has just had its front springs and hangers replaced says that it is hard to keep the steering wheel in a straight-ahead position. Technician A says the cause could be that the caster shims were installed backward. Technician B says the problem could be that the wrong spring hangers were installed. Who is right?
A.    A only
B.    B only
C.    Both A and B
D.    Neither A nor B

2. The driver of a school bus says that it is too hard to steer and that the steering wheel return is too fast. Which of these is the most likely cause?
A.    Too much negative caster
B.    Too much positive caster
C.    Too much negative camber
D.    Too much positive camber

A common power problem with diesel engines.
3. The driver of a school bus with a diesel engine complains of a lack of power. What should the technician check first?
A.    The injection nozzle pressure
B.    The injection pump timing
C.    The fuel filter pressure on the
    outlet side
D.    The injection pump calibration

4. A technician is road-testing a school bus with a diesel engine. He notices that it blows black smoke when under heavy load. Which is the least likely problem?
A.    Late injector pump timing
B.    A restricted air intake
C.    Worn injectors
D.    A clogged fuel filter

This is probably the most important electrical system lesson you can learn.
5. A school bus has suffered premature alternator failure. The battery and vehicle wiring show no problems, but the driver has several times left the lights on overnight. Each time, the bus was jump-started and sent back out. Technician A says that the alternator was probably defective and that replacing it should correct the problem. Technician B says that the vehicle’s battery should have been slow-charged before sending the bus back out. Who is correct?
A.    A only
B.    B only
C.    Both A and B
D.    Neither A nor B

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Answers

1.    A is the answer. The caster is critically important in keeping tires at the correct angle.
2.    B. Caster is the most critical in alignment specifications, because it affects the steering wheel’s ability to return to center.
3.    C. Because filters are easily clogged, check the outlet pressure first.
4.    D. A clogged fuel filter will reduce fuel flow and power.
5.    B. An alternator is designed to handle high accessory loads and only light charging loads, especially after jump-starting — the alternator could very well be overloaded and overheated. Slow-charging the new style batteries for eight hours minimum when they are found dead is essential for restoring the electrical system back to normal. Simply jump-starting a bus and sending it out is a recipe for a road call