Volvo MD5A Workshop 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 SI­units. The units used previously however, are also stated but in brackets.

The new units are:

Output is slated in kW (kilowat ts)

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 dm

earlier unit l (litres)

Pressure is stated in Pa (Pascal)

earlier unit kp/cm2 (kiloponds per square centimetre).

Reproduction permitted if source quoted

3 (

cubic decimetres)

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 adjus tment 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

1. Connection for hand start

2. Fuse box

3. Thermostat housing

4. Decompression lever

5. Injector

6. Oil filler Cap, engine

Presentation

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 fu el 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

17. Remove the main bearing caps. Take care of the axial

thrust bearings 1 on the transmission side. Lift the crank shaft
out and the bearing shells afterwards and then the axial
bearing halves.

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).

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 gear wheel 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

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.

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.

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