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July 18, 2013  |   Comments (4)   |   Post a comment

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.

by David Anderson


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David Anderson is director of transportation and fleet service at Adams 12 Five Star Schools in Thornton, Colo. Since he started his pupil transportation career in 1981, he has also served in the positions of mechanic, shop foreman and fleet manager.
<p>David Anderson is director of transportation and fleet service at Adams 12 Five Star Schools in Thornton, Colo. Since he started his pupil transportation career in 1981, he has also served in the positions of mechanic, shop foreman and fleet manager.</p>

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


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


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Brian, I accept your corrections of my statements completely and realize that B. is the correct answer for #5. My very first day of school bus driving was in a 1947 International Harvester 48 Passenger Superior and my training consisted of riding along as students were being taken home from school. When half the students had been dropped off the bus driver stopped the bus going up a hill and said it was my turn to drive. I had never heard of a spur gear transmission and double clutching and I was expected to learn starting up the hill with students. By the time I retired in 1998 I had spent my years with the motto, "Your Child's Safety Is Our First Concern".

Dwight -- DSBSI ltd.    |    Jul 31, 2013 01:33 AM

Charles (or is it Dwight? I'm confused), I agree that the driver needs to learn not to leave the lights on; however, when you say that the alternator "will provide amperage to the battery at the rate the battery will except", don't you think the battery (actually 2-3 batteries) will accept more amperage than the alternator is rated at when they are flat dead? That's what you call "full-fielding" the alternator, which can cause failure. That's alternator 101 (although we all do it on occasion...) Finally, what they are referring to as "new-style" batteries, I think, are the sealed kind without filler caps. If you slap 200 amps to them for an extended period, you can't replace the acid that boils off.

Brian Alexander    |    Jul 30, 2013 07:45 AM

Great test I would like to see more.

Charles Glenn    |    Jul 19, 2013 06:03 AM

The answer to #5 should be D. Neither A nor B The driver has a history of not performing the job correctly and should have been retrained and then found incompetent to safely operate the school bus as the problem repeated. As for the battery problem, the alternator is regulated at 14volts and will provide amperage to the battery at the rate the battery will except. If the 'new style batteries' are not compatible for school bus use a change must be made in specifications. It is unlikely the alternator would require a high accessory load just starting out and the driver should be cautioned to keep interior heating or cooling fans at a minimum as needed on this day. A driver is operating at a higher level of safety with the regular bus that has the seat & all mirrors adjusted to fit this driver for line of sight & all switches and instruments in the familiar location. A school bus should meet specifications that allows a simple way of shutting down all systems to eliminate a dead battery. Dwight

Dwight -- DSBSI ltd.    |    Jul 18, 2013 07:11 PM

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