MOTOR ANCILIARIES EXERCISE: QUESTIONS ONE NAME:

1. Explain why a ‘blower’ is needed to allow a diesel two-stroke to operate, but not needed on a petrol two-stroke.

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2. What is the quickest way to stop a diesel engine if the cut off solenoid becomes inoperable?

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3. Name two purposes of lubrication in a marine diesel engine:

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4. When started, a cold engine will have a _________ oil pressure which will cause the relief valve to _________.

5. What are 3 possible lubricating system faults?

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6. What is an indication of a leak in a fresh water cooler tube?

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7. How can a two-stroke diesel engine use an oil filled ‘wet-sump’ for lubrication, but a two-stroke petrol engine must have a ‘dry sump’ and use other methods to lubricate the engine?

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ANSWERS ONE

1. Explain why a ‘blower’ is needed to allow a diesel two-stroke to operate, but not needed on a petrol two-stroke.
The petrol engine uses the suction in the sealed crankcase to draw fuel/air into the engine. The diesel need a blower to force air directly into the cylinder.

2. What is the quickest way to stop a diesel engine if the cut off solenoid becomes inoperable?

Block off the air intake.

3. Name two purposes of lubrication in a marine diesel engine:

Cooling, reducing friction, removing debris from the action of wear and combustion.

4. When started, a cold engine will have a high oil pressure which will cause the relief valve to open.

5. What are 3 possible lubricating system faults?

No oil, damaged oil pump, ineffective oil cooler, faulty oil pressure relief valve, engine wear.

6. What is an indication of a leak in a fresh water cooler tube?

Oil floating on top of the fresh water in the header tank.

7. How can a two-stroke diesel engine use an oil filled ‘wet-sump’ for lubrication, but a two-stroke petrol engine must have a ‘dry sump’ and use other methods to lubricate the engine?
The petrol engine uses the sealed crankcase as part of the fuel/air induction path. The blower on the diesel forces air directly into the cylinder.

QUESTIONS TWO

1. Describe the problems associated with using raw sea-water to cool a marine engine. (You can list possible solutions to these too, if you wish.)

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2. Compare skin tank cooling to keel cooling.

(a) Make a list of problems associated with keel cooling pipes, whether in the open or covered with channel. What effect would marine growth have on keel cooling?

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(b) Does skin tank cooling overcome these problems? Is rust or corrosion a potential problem for skin tanks?

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3. With heat-exchanger cooling, what precautions must be taken in relation to the raw water path? See the article, Engine water cooling systems.

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4. What advantage does the air oil cooling system have over a system which uses raw water to cool the oil? Hint: Think about the oil operating temperature. See the article, Lubrication systems.

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5. State the problem which may be caused if a heat exchanger is too effective, and describe how this problem is normally overcome.

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ANSWERS TWO

1. Describe the problems associated with using raw sea-water to cool a marine engine. (You can list possible solutions to these too, if you wish.)
Salt-water is highly corrosive. Brass, stainless or anti-corrosive engine treatments must be used.
Weed and marine animals can block the inlet. Weed traps, strainers, and routine maintenance keeps them clean.
Metals can be eaten away by electrolytic action in sea water. This problem is reduced by using special metals and zinc electrodes for protection.

2. Compare skin tank cooling to keel cooling.

(a) List problems associated with keel cooling pipes, whether in the open or covered with channel. What effect would marine growth have on keel cooling?
They can be damaged. They penetrate the hull. Marine growth reduces the cooling efficiency.

(b) Does skin tank cooling overcome these problems? Is rust or corrosion a potential problem for skin tanks?
Skin tanks are more protected, and do not penetrate the hull, but they are still less effective with marine growth on the hull.

3. With heat-exchanger cooling, what precautions must be taken in relation to the raw water path? See the article, Engine water cooling systems.

Must be kept clean and free of weed and marine organisms.

4. What advantage does the air oil cooling system have over a system which uses raw water to cool the oil? Hint: Think about the oil operating temperature. See the article, Lubrication systems

The oil can stay at operating temperature, where raw water might cool it too much.

5. State the problem which may be caused if a heat exchanger is too effective, and describe how this problem is normally overcome
The engine might be cooled too much. Thermostats may be used to allow the engine to warm up properly

QUESTIONS THREE

1(a) Outline the operation of the wet sump force-feed lubrication system. See the article, Lubrication systems

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(b) If you start an engine with the Caterpillar lubricating system, and the oil pressure gauge reads very high, state what might be the cause of the problem.

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(c) If you start an engine with the Caterpillar lubricating system, and the oil pressure gauge reads very low, state what might be the cause of the problem.

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(d) What is the main problem if the oil filter should become blocked due to unsatisfactory maintenance?

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2(a) What is the function of a sediment bowl or sludge trap, and how does it work?

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(b) What contaminants will a sediment bowl collect?

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3.         In the diaphragm fuel pump shown above, tick the components which actually force fuel through the outlet.
         Diaphragm and Diaphragm Spring
         Diaphragm and Rocker Arm Lever

4 Some diaphragm pumps have a glass cover over the top. State two advantages of using a glass cover, rather than a metal one.
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5. What could happen to the lubricating and fuel oil systems if a hole or split occurred in the diaphragm of a fuel lift pump? (In the diaphragm fuel pump shown above)
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6. You suspect that water and muck may have got into the fuel tank through a bad batch of fuel. Where would you open drains and check filters to find out?

Drains:

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Filters:
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7. The engine appears to be starving for fuel. Identify the first thing you would check?

Install a pressure gauge and measure fuel pump outlet pressure

a. Check the level of fuel in the tank

b. Check pipes and unions for kinks, damage, leakage and tightness

c. Disconnect the pump and measure fuel flow rate

d. Check filters and strainers

8. “The high pressure output from gear type lubrication pumps is limited to a maximum value by increasing gear clearances!”

TRUE FALSE

9. Tick the most correct statement below:

a. Filters are changed when they begin to show signs of blockage.

b. Filters are changed if a batch of contaminated fuel/oil has been used.

c. Filters are changed when specified by periodic service schedules

d. Filters are changed for all of the above conditions.

10. “Bleeding of diesel fuel systems involves the removal of air from all lines and components starting at the tank end and ending at the injectors!”

TRUE FALSE

11.       If a petrol marine engine stops because sea-water has found it’s way into the carburettor, what will you most likely have to do?
a.         Drain the sludge filters and re-start the engine.
b.         Get out and push-start the vessel.

c. Drain water from the tank, sludge filters and carburettor bowl, and remove and clean all jets

12. Complete the following statement. “The needle valve and float in the carburettor bowl, is used to:

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ANSWERS THREE

1. (a) Outline the operation of the wet-sump force feed lubrication system
The oil pump draws oil from the sump and pumps it to the engine through a filter. It flows around the engine galleries and lubricates all parts. The oil then drains back and collects in the sump of the engine, ready to be circulated again.
(b) If you start an engine with this lubricating system, and the oil pressure gauge reads very high, state what might be the cause of the problem
The oil pump relief valve could be stuck shut. The oil may be the wrong grade.

(c) If you start an engine with the Caterpillar lubricating system, and the oil pressure gauge reads very low, state what might be the cause of the problem.

No oil, Worn cylinders, Damaged rings, Damaged oil pump, very cold, Oil leak.
(d) What is the main problem if the oil filter should become blocked due to unsatisfactory maintenance?
The bypass valve will open and feed unfiltered oil into critical engine components.

2. (a) What is the function of a sediment bowl or sludge trap, and how does it work?
Water and muck which is heavier than the fuel will sink, and collects at the bottom of the filter. From there it can be removed by undoing a drain valve and draining it into a container.

(b) What contaminants will a sediment bowl collect?
Water, dirt, metal particles, and anything heavier than the fuel.

3.         In the diaphragm fuel pump shown in Figure 30, tick the components which actually force fuel through the outlet.
            Diaphragm and Diaphragm Spring
            Diaphragm and Rocker Arm Lever

4. Some diaphragm pumps have a glass cover over the top. Can you suggest two advantages of a glass cover, rather than a metal one?

You can see if the pump is delivering fuel or pumping air. You can see if water and muck is being pumped from the tank.

5. What could happen to the lubricating and fuel oil systems if a hole or split occurred in the diaphragm of a fuel lift pump? (In the diaphragm fuel pump shown above)
The fuel system and lubricating systems would contaminate each other through the hole in the diaphragm. This could show up as diluted lube oil, or clouds of blue smoke form the exhaust.

6.         You suspect that water and muck may have got into the fuel tank through a bad batch of fuel. Where would you open drains and check filters to find out?
Drains                            Filters
Main tanks..                    Primary fuel filter (sludge filter) .
Service tanks                   Secondary fuel filter
                                       Primary Filters

7. The engine appears to be starving for fuel. Identify the first thing you would check?

a.    Install a pressure gauge and measure fuel pump outlet pressure
b.    Check the level of fuel in the tank
c.    Check pipes and unions for kinks, damage, leakage and tightness
d.    Disconnect the pump and measure fuel flow rate

e. Check filters and strainers

8. “The high pressure output from gear type lubrication pumps is limited to a maximum value by increasing gear clearances!” FALSE

9. Tick the most correct statement below:

a. Filters are changed when they begin to show signs of blockage.
b. Filters are changed if a batch of contaminated fuel/oil has been used.
c. Filters are changed when specified by periodic service schedules
d. Filters are changed for all of the above conditions.

10. “Bleeding of diesel fuel systems involves the removal of air from all lines and components starting at the tank end and ending at the injectors!”

TRUE

11.       If a petrol marine engine stops because sea-water has found it’s way into the carburettor, what will you most likely have to do?
a.    Drain the sludge filters and re-start the engine.
b.    Get out and push-start the vessel.
c.    Drain water from the tank, sludge filters and carburettor bowl, and remove and clean all jets

12. Complete the following statement. “The needle valve and float in the carburettor bowl, is used to - maintain a relatively constant fuel level for the jets of the carburettor, to keep the fuel/air mixture in the correct proportion