Volvo MD5A, Workshop Manual

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FAULT TRACING
The fault finding chart given below only covers the most common faults which occur.
Engine will not start Engine stops The engine does not reach the correct speed at full throttle The engine runs rough or vibrates abnormally The engine becomes abnormally hot
FAULT Note
X Main switch not connected, flat battery, cable
disconnected. See para A
X X Empty fuel tank, fuel tap closed, blocked fuel
filter. See para B
X X X Water, air or impurities in the fuel.
See para B
X X X X
Faulty injector.
See para C
X Boat abnormally loaded, boat bilge fouled with
weedgrowth. See para C
X X
Propeller damaged.
See para E
X Clogged coolant water intake, cooling vanes,
defective pump wheel or thermostat. See para F
A. Check the charge state of the battery with the help of a
hydrometer which shows the specific gravity of the
battery acid. This varies according to the state of the
charge, (see the technical data). (See furthermore
“Electrical system” p. 26.)
B. Change the microfilter by unscrewing the hexagonal
head on the filter holder’s base. The microfilter and its
holder are of a discardable type which means that the old
filter is discarded and a new one fitted. Check that the
face of the cover is completely clean and that the filter
packing is undamaged. Screw the new filter by hand until
the packing contacts the cover. Then tighten the filter a
further half turn. There is a drain plug in the bottom of the
filter holder for draining water and impurities in the fuel.
Bleed the fuel system after draining and after a filter
change and then check for tightness.
Remove the cover on the feed pump and clean the pre-
filter in diesel oil. Refit the filter with the notches upward
and fit an undamaged packing and tighten the cover.
Bleed the fuel system.
Check and drain when necessary the extra fuel filter if
one is fitted. Look out for spilled fuel.
C. Check the injector with reference to opening pressure,
tightness and jet shape. It is recommended that these
checks be carried out after a maximum operation time of
400 hours or once per season. See also paragraphs 55
and 56.
D. To obtain the best operational economy, the engine
speed should be at least 300 r.p.m. less that the
maximum obtainable during extended running periods.
Note! If the boat has been in the water a considerable
time, the maximum obtainable engine speed can
decrease due to growth on the hull’s underside. Use
growth inhibiting bottom paint.
Check and clean the hull regularly.
E. Check that the propeller blades are whole. If any of the
propeller blades are damaged, the propeller should be
changed. A propeller blade can be out of line (twisted)
—
this is very difficult to detect. Place the propeller on a flat
surface and measure the blades. If any blade is twisted
the propeller should be changed.
F. Check the coolant system from the point of view of
leakage, blockage etc.
Check that the thermostat opens at the correct tempera-
ture. The thermostat can be taken out when the
thermostat housing has been dismantled. See also
paragraph 84.
The pump impeller in the sea water pump is made of
neoprene rubber and can be damaged when the water
supply is cut off, for instance if there is a blockage in the
sea water intake. Paragraphs 23—27 should be followed
when changing a pump impeller and sealing rings. Note)
If the boat is in the water the sea cock must be closed
before the sea water is dismantled. Do not forget to open
the cock again.
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