Volvo MD5A Instruction manual

Publ. No. 3061
Dec. 1975
WORKSHOP MANUAL
MD5A
Marine diesel engine
ENGINE UNIT

FOREWORD
This workshop manual contains repair instructions for the MD5A marine diesel engine. The instructions
concerning overhauling describe the most suitable working method to be used with the special tools listed under
the heading “Special tools”.
Both the engine designation and its serial number must be clearly stated in all correspondence concerning the
engine and when ordering spare parts. We reserve the right to carry out design modifications and, for this
reason, the contents of this manual cannot he regarded as binding.
AB VOLVO PENTA
Technical Information Department
NEW UNITS OF MEASUREMENT
Technicians have long since tried to establish an internationally standardized system of
measurements. In 1960 a decision was made to use a system called SI (Systéme International
d’Unites). To a large extent, this system is based on earlier systems but the units have been
made uniform so that no conversions are necessary.
The SI-system is now being applied within industry in Europe, This manual contains the new SI-
units. The units used previously however, are also stated but in brackets.
The new units are:
Output is slated in kW (kilowatts)
earlier unit h.p. (horsepower)
Torque is stated in NM (Newton-metres)
earlier unit kpm (kilopond-metres)
Engine speed is stated in r/s (revolutions per second)
earlier unit r.p.m. (revolutions per minute)
Displacement and volumes are stated in dm3 (cubic decimetres)
earlier unit l (litres)
Pressure is stated in Pa (Pascal)
earlier unit kp/cm2 (kiloponds per square centimetre).
Reproduction permitted if source quoted

CONTENTS
Presentation 2
Dismantling
Electrical system, thermostat housing cylinder head 3
Flywheel, fuel injector pump 4
Oil pump, transmission cover, governor 5
Lubricating oil pump, camshaft, cylinder 6
Crankshaft, cylinder liner, camshaft bearing 7
Overhauling
Lubricating oil pump, sea-water pump 7 –9
Feed pump 9 –11
Fuel filter, crankshaft 11
Centrifugal governor, piston 12 –13
Valve guides, nozzle sleeve 14 –15
Valves, valve seats, rocker mechanism, injector 15 –16
Hand start mechanism, camshaft 17
Assembling
Cylinder liner, crankshaft 18
Cylinder, camshaft, governor 19
Lubricating oil pump, transmission cover 20
Adjustment of control rod travel, assembling
flywheel cover 20 –21
Oil sump, cylinder head, feed cover 22
Fuel filter, injector, thermostat 22
Flywheel, generator, valve adjustment 24
Checking injection angle 25
Bleeding the fuel system, electrical system 26
Wiring diagram 27
Fault-tracing system 28
Special tools 29
Technical data 30 –33

Presentation
1. Connection for hand start
2. Fuse box
3. Thermostat housing
4. Decompression lever
5. Injector
6. Oil filler Cap, engine
7. Water drain tap, gearbox
8. Oil drain plug, gearbox
9. Water drain tap, engine
10. Oil filler, gearbox
11. Sea-water pump
12. Dipstick, gearbox
13. Fuel filter
14. Bleed screw
15. Hand pump, fuel
16. Dipstick, engine
17. Oil filter
2

Repair instructions
Dismantling
1. Drain the cooling water and the oil from the engine. Clean
externally afterwards. Loosen the water hose between the
gearbox and the sea-water pump and remove the gearbox.
3. Remove the rocker cover and the fuel pipe between the
pump and the injector and unscrew the rocker gear. Note!
Pull the rocker gear straight up since it is centred with a
guide pin 1. The other hole 2 is an oil channel.
2. Remove the generator and its drive belt, starter motor,
fuel filter and fuel pump with the drain-off pipe (be careful of
fuel spillage), coolant water pump with hose and thermostat
housing, dipstick, temperature and oil pressure sensors.
Unscrew and discard the oil filter.
4. Remove the push-rods 1, remove the cylinder head and
the cylinder head gasket. Take care of the washers 2 under
the nuts.
3

5. Remove the flywheel nuts. Spanner jaw width 55 mm
(2 5/32”). Use a wooden shaft or something similar as a
counter force in the flywheel spokes.
7. Remove the cover for the injection pump. Note! The
bracket for the cold start is fixed with one of the screws.
Take care of the spring under the cover.
6. Fit tool 884078 to the flywheel. Afterwards screw in the
centre screw on the tool until the flywheel loosens.
8. Prise the lower ball joint free from the pump with a
screwdriver.
4

9. Remove the pump screws. Position the ball in the centre
and remove the pump. 11. Remove the governor by loosening the hexagonal set screw (1), the governor and the gear wheel can then be
withdrawn.
10. Remove the sump and then the transmission cover (13
screws). The lifting eye is fixed one of the screws. The cover
is centralised by guide pins.
12. Remove the screw and the locking washer for the
gearbox drive flange on the crankshaft and remove the
flange with a puller. (Use counter force.) Remove the key
afterwards.
5

13.Remove the lubricating oil pump. Discard the gasket. 15. Remove the gearwheel on the camshaft’s flywheel side
(4 screws). Then remove the camshaft and the gearwheel.
14. Remove the cover (flywheel side), 10 screws. The cover
is centred with guide pins. The screws by the guide pins are
fitted with thick washers.
16. Mark and remove the bearing cap on the crankshaft and
carefully knock out the piston through the cylinder.
6

19. Bearing replacement. Press out the camshaft bearings if
they are damaged or if the wear is too great (see technical
data). Clean the bearing housings and ensure that the oil
channels are clean. Press in the new bearings so that the oil
holes face the corresponding oil channels in the block. When
the bearings are pressed in position they are to be reamed
(see technical data).
17. Remove the main bearing caps. Take care of the axial
thrust bearings 1 on the transmission side. Lift the crankshaft
out and the bearing shells afterwards and then the axial
bearing halves.
18. Mark the cylinder liner’s position in the cylinder so that
the same position can be obtained during assembly.
Remove the cylinder liner. Use tool 884551. Use the long
screw and its nut from the tool 884231 (MD21-MD32). See
page 29 Special tools. Discard the 0-ring. Afterwards remove
the 0-rings in the block which provide a seal for the cylinder
liner and then remove the valve lifters. Wash all the parts
and replace those damaged.
Oilpump
20. Remove the gearwheel’s nuts and pull off the gearwheel
with a puller. The gearwheel sits on a key, take care of this
key.
7

21. Remove the steel wire which holds the filter. Remove
and clean the wire gauze thoroughly. Afterwards remove the
six screws which hold the cover in position. Discard the
gasket.
Overhauling the sea-water pump
23. The sea-water pump is a round flange type pump which
means that it can be fitted in a position best suited to the
coolant water hoses. The new pump is fitted with an 0-ring
which forms a seal against the engine.
22. Remove the gearwheel from the housing. Remove the
split pin for the reduction valve. Remove washer 1, spring 2
and piston 3. Clean and replace damaged parts. Assemble
the lubricating oil pump in the reverse order. Note! Fit a new
gasket 4 between the housing and the cover. Fix the wire
mesh 5 in position with the steel wire 6 and finally lay the key
in position and tighten the gearwheel 7.
24. Remove the cover (6 screws). Change the impeller with
the help of two screwdrivers or something similar. Note!
Protect the edges of the pump housing. See the figure. Prise
out the impeller with the screwdrivers so far that the screw
becomes visible.
8

27. Fit new sealing rings. Note! The sealing rings must face
the right way, see that they do not block the drain hole in the
pump housing. Smear grease on the shaft and fit it carefully
in the housing. Screw it through the sealing rings so that
they will not be damaged. Place the shaft so far into the
housing that the hole for the screw is visible. Fit the impeller
and screw in the screw. Then carefully press in the impeller
so that it touches bottom. Place a new gasket on the cover
and tighten the cover with the six screws.
25. Unscrew the screw and withdraw the impeller from the
shaft. If the sealing rings are to be replaced, the shaft and
the impeller can be removed and the screw subsequently
loosened.
26. Remove the sealing rings 1 and the 0-ring 2 (earlier
engines) and clean the housing and the shaft. (Note! The
pump must be removed from the engine.) Check that there
are no abrasions on the shaft. Note! A new 0-ring is not to be
fitted.
Overhauling the feed pump
28. Depress the pump’s lever (see fig.). If the pump “creaks”
then it is sound. If it is unserviceable the diaphragm must be
replaced which is done in the following manner:
9

29. Remove the cover’s centre screw, remove the filter 1
and clean it.
31. Depress the diaphragm and shake the pump arm
spindle out until the pump arm is free. Then remove the
diaphragm from the housing.
30. Remove the six screws which hold the upper and lower
pump halves together. Remove the pump’s spring and undo
screw 2 which holds the pump arm spindle.
32. Remove screw 1 and withdraw the manual pump arm 2
and replace spring 3 if it is broken. Note! Be careful of the
rubber seal which is pressed into the housing.
10

33. Clean the pump housing carefully and replace worn
parts. Refit the manual pump arm. Press in the diaphragm
and connect the pump arm to the diaphragm centre pin.
Then push the spindle in and tighten it with the screw. Note!
Do not forget thewasher under the screw.
Lay the gauze filter on the upper housing and screw the
cover and the gasket tight. Press in the pump arm 3,
assemble the two housing halves and fit the spring retainer 2
on the mechanical pump arm 3. Note that the spring retainer
can only be fitted one way. Replace the spring next and the
0-ring 4 which provides a seal for the engine.
Crankshaft
35. Remove the circlip with circlip pliers. Then remove the
gear drive. Use a press or a gear puller. Clean the
crankshaft and carry out control measurements of all the
bearing surfaces. Grind the shaft where necessary. See
technical data.
Fuel filter
34. When the filter insert is changed the centre screw 1 is
removed allowing the filter holder to be removed. Afterwards
remove the filter insert by lifting the plastic loop 4. Wash the
filter holder clean and fit a new filter. Fit a new packing
washer 5 and refit the holder to the cover with the centre
screw.
36. Place the key in the crankshaft’s key slot. Heat the
gearwheel to approximately 1000C (2120F) (no more) and
press it onto the crankshaft. Note! The marking on the
gearwheel shall face outwards. Refit the circlip on the
crankshaft.
11

Centrifugal governor
37. Clean the governor. Check to see if the weights 2 grip
on their spindle or if there is too much movement between
the spindle and the governor weight. Afterwards check that
the pin 1 slides easily in the spindle. Finally check both the
ball bearings 3. Replace the ball bearings if they are tight.
Check that all the movable parts move easily, lubricate and
refit them in the reverse order.
39. Mark the piston and the connecting rod. Remove the
circlips. Press out the gudgeon pin with a drift. (The piston
can be heated first to ease removal.)
Piston
38. Remove the piston rings with the help of piston ring
pliers. Clean the piston and be particularly careful about the
piston ring grooves.
40. Press the bush out of the connecting rod if it is worn or
damaged. Then knock out the connecting rod screws. Note!
The screws must always be changed when the connecting
rod has been dismantled.
12

41. Knock new screws in place and press a new bush in the
connecting rod. Ensure that the lubricating hole 1 in the bush
aligns with the hole in the connecting rod. Ream or diamond
drill the bush to an accurate free fit. Check that the gudgeon
pin slides through the bush due to its own weight. (See also
the technical data.) Fit one of the circlips and oil the gudgeon
pin and connecting rod bush. Heat the piston to
approximately 700C (1580F) and assemble the piston and
the connecting rod according to the marking. Note! The
gudgeon pin must be able to be pressed in easily. Fit the
other circlip.
43. Fit the piston rings with the help of piston ring pliers.
Start withthe oil scraper ring in the lowest groove. The oil
scraper ring can be fitted either way. Continue with the
compression ring which is marked “TOP” on one side. This
marking shall face upwards when fitted. The piston ring with
the chromium insert is fittedlast and can be fitted either way.
Cylinder head
44. Remove the collets, the collars and the valve springs
with the help of a valve spring compressor. Remove the
valves. Remove the valve seal from the inlet valve. Burnt
valves are discarded if worn too much and damaged seats
are to ne machined when necessary. (See technical data.)
The valves and valve seats are to be ground together so that
the mating surfaces provide a complete seal.
42. Control the dimensions of the piston with a micrometer.
Measure at right angles to the gudgeon pin holes at the
piston’s lower edge. Afterwards check the new rings’ play in
the piston ring grooves. (See technical data.)
13

Replacing valve guides
45. The valve guides must be replaced if there is too much
play between the valve stem and the valve guide. (See
technical data.) Press out the valve guides with tool 884538.
Nozzle sleeve
47. Remove the injector sleeve with tool 884541. Insert the
expanding screw in the nozzle sleeve and screw anti-clock-
wise until the screw has expanded and gripped the sleeve.
Tighten hard so that the threads bite into the copper. Fit the
yoke onto the studs which hold the nozzle. Screw on the nut
and tighten until the sleeve is removed.
46. New valve guides are fitted with tool 884549. Use a
press. This tool gives the guide the right height above the
cylinder head’s valve spring seat surface. Check the dimen-
sion “A” -this must be 9 mm (0,3543 in.) when the guide is
pressed into place.
48. Remove the 0-ring which provides a seal between the
sleeve and the cylinder head. Clean carefully and dry with
compressed air and then dip the new 0-ring in a soap
solution to facilitate assembly. Lubricate and fit the new
nozzle sleeve with tool 884557. Knock in the sleeve until it
reaches bottom.
14

Valve and valve seat grinding
51. Machine the valve seats by milling or grinding them.
Grind no more than is necessary to give the seat the correct
shape and a good mating surface. The seat angle C shall be
45°and the width “B” approximately 1 mm (0,0394 in.). The
width is adjusted with a 39°and a 60°miller respectively or
a grinding disc. Clean the valves and grind them in a
machine. The valves’ face angle D shall be 44,5°. The
sealing surface is ground no more than is necessary to
“clean” it. If less than 1 mm (0,0394 in.) is left on the valve
edge it is to be discarded. Likewise the valve is discarded if
the valve stern is not straight or if dimension “A” exceeds 2,5
mm (0,0984 in.). Note! If this dimension is exceeded even if
a new valve is fitted, the cylinder head must be changed.
49. Lubricate the mandrel tool 884537 and insert the tool
into the sleeve. (Ensure that the centre screw is sufficiently
unscrewed.) Place some nuts or several washers on the
studs so that the yoke can be tightened in place with the
fixing nuts. Screw in the mandrel as far as the mating face of
the sleeve allows. The mandrel is then withdrawn. Remove
the tool.
50. Adjust the length of sleeve protruding from the cylinder
head face, (length is 0,9 mm) (0,0354 in.) and check that the
sleeve is correctly fitted (dimension 19,5 mm). (0,7677 in.).
Rocker mechanism
52. Remove the circlip from the rocker shaft and remove the
rocker arms. Clean the parts. Be particularly careful when
cleaning the rocker shaft oil channels 3 and the rocker arm’s
oil hole, see also fig. 53.
15

53. Check the wear on the rocker shaft. Also check that the
tappet adjustment screw’s spherical part is neither deformed
nor worn. The threads on the screw and the locknut must be
undamaged.
Oval rocker arm bushes are to be replaced. Pressing in and
out is performed with drift 884560. Press the bush in so that
the oil hole assumes the position shown in the figure. The
bush is reamed to a light push fit after it has been pressed
in. Lubricate the shaft and assemble the rocker mechanism.
Pressure testing the nozzles
55. Check the shape of the jets at an opening pressure of
185 kp/cm2 (2631 p.s.i.). Also check that the fuel spray
discontinues simultaneously at all four holes and that no
subsequent drops appear.
Adjustment of opening pressure
56. The opening pressure is adjusted with adjustment
washer 1, which is available in thicknesses between 1 mm
(0.0394 in.l and 1,95 mm (0.0768 in.) with a difference of
0,05 (0,0020 in) mm between each size. Dismantle the
nozzle and replace the washer with a thinner or thicker
washer depending on whether the pressure is to be reduced
or increased. Assemble the nozzle and check the opening
pressure and jet shape. Continue until a satisfactory result is
obtained.
54. Fit the rubber seal 1 on the inlet valve. Use tool 884497.
Oil the valve sterns before they are inserted in their
respective valve guides. Afterwards fit the valve springs,
collars and collets with the help of a valve compressor.
16

Flywheel cover and hand starting mechanism
57. Unscrew nut 1 and remove it and washer 2 holding the
hand starting gearwheel 3. Then remove the gearwheel from
the shaft A. Knock the shaft out from the cover. Loosen the
set screw 5 which holds the spacer washer and knock out the
spacer washer when the bearings 7 has been removed.
Remove key 8, slide off the spacer ring 9 and pull off ball
bearing 10 after which seal 11 can be pulled off. Note! If only
the seal 11 is to be changed, pin 12 can be knocked out, after
which the seal can be removed.
58. Replace damaged parts and reassemble the pin, seal,
ball bearing and spacer ring on the shaft. Fit the spacer
washer into the cover and tighten it in position with the set
screw. Note! Ensure that the spacer washer’s groove faces
the locking screw’s centre. Fit the shaft in the cover. Place the
key in position and then the ball bearing. Fit the gearwheel.
Secure it with a washer and nut. Knock out seal 1 from the
flywheel cover. Press in a new seal afterwards.
Camshaft
59. In such cases (on engines with engine nos. 100-1075)
where a camshaft gear change is necessary, the camshaft
must be changed as well. A new camshaft gear cannot be
fitted to an early type of camshaft. Furthermore this means
that the transmission cover must be machined since the
new camshaft gear is thicker than the earlier gear and
consequently there is not enough space for it in the
transmission cover. The axial guide face distance A must be
filed down by 3mm (0,1181 in.).
If the camshaft is damaged this means that the camshaft
gear must be replaced in this case as well. This also means
that the axial guide face must be filed down by 3 mm
(0,1181 in.).
60. If the transmission cover is damaged and must be
replaced, this means that even the camshaft and the
camshaft gear must be replaced. The replacement is
necessary because the axial guide in the new transmission
cover is shortened by 3 mm (0,1181 in.) which in turn
means that the camshaft will have an axial play of 3 mm
(0,1181 in.).
The camshaft, camshaft gear and transmission cover are
interchangable as of engine no. 1076 inclusive. When
changing camshaft gears of a later type, the camshaft shall
be pressed out of the camshaft gear.
Take care of the key. Check the camshaft for wear. See the
technical data.
Place the key in the camshaft and press on the camshaft
gear. The distance from the camshaft end to the camshaft
gear’s hub must be 136 mm (5,354 in.). See fig.
17

ASSEMBLING
61. Check that the liner is not scratched and that it is in
good condition otherwise. Fit new 0-rings 1 in the block (2
off) and a new 0-ring 2 on the cylinder liner. Turn the mark
on the liner (which was made during dismantling) to the mark
on the block. Lubricate the 0-rings and fit the liner. Be careful
not to damage the 0-rings.
63. Place the main bearing halves with the oil channel holes
in the block. Then place the axial bearing halves in position.
Turn the oil grooves 1 outwards.
64. Oil both the bearing halves and place the crankshaft in
position. Fit the main bearing shells in the bearing housings
and place the axial bearings with the oil grooves outwards.
Fit the bearing housing so that the indentation in the housing
faces the same way as the indentation in the bearing half
already in the block. Tighten the bearing housing with a
torque of 70 Nm (7 kpm) (50 Lbft.).
62. When the cylinder liner is fitted in the block the height of
the liner outside the block must be measured. The height
must not exceed 0,05 mm (0,0020 in.) and must not be less
than 0,01 mm (0,0004 in.), otherwise there is a risk that a
leak can occur.
18