Northern Lights Lugger OM673 User manual

OM673
For Models: M673M, M673D, and M673L
OPERATOR’SMANUAL
Marine Generators | Marine Diesel Engines | Land-Based Generators

Diesel engine exhaust and some of its constitu-
ents are known to the State of California to cause
cancer, birth defects, and other reproductive harm.
— CALIFORNIA —
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Northern Lights
4420 14th Avenue N.W.
Seattle, WA 98107
Tel: [phone]
Fax: [phone]
Copyright ©2009 Northern Lights, Inc.
All rights reserved. Northern Lights™, and
the Northern Lights logo are trademarks of
Northern Lights, Inc.
Printed in U.S.A.
PART NO.: OM673 09/09

OM673 09/09
Read this operator's manual thoroughly before starting to operate your equipment.
This manual contains information you will need to run and service your new unit.
OPERATOR'S MANUAL
for Models
M673M, M673D, and M673L
INTRODUCTION ....................................................2
Models Included .................................................2
Model Numbers..................................................2
Serial Numbers ...................................................2
WARRANTY ............................................................3
SAFETY RULES.....................................................3
COMPONENT LOCATIONS
M673 Marine Generator.....................................4
PANELS
Northern Lights Generator Sets....................5 - 6
OPERATING PROCEDURES
Break-in Period...................................................7
Before Starting....................................................7
Starting................................................................7
Operating ............................................................7
Stopping..............................................................7
Shutdowns and Alarms .......................................8
Spare Parts..........................................................8
SERVICING SCHEDULE CHART.......................9
SERVICING
Lubrication - General........................................11
Checking Oil.....................................................11
Oil Changes ......................................................11
Changing Oil Filter...........................................11
Air Filter .......................................................... 12
V-Belts ............................................................. 12
Valve Clearances.............................................. 12
SERVICING (CONTINUED)
Fuels - General................................................. 13
Fuel Filters....................................................... 13
Bleeding the Fuel System................................ 14
Injector Service........................................ 15 - 16
Injection Pump................................................. 16
Cooling System - General................................ 16
Cooling System Flushing................................. 17
Heat Exchanger ............................................... 17
Raw Water Pump ............................................. 17
Generator Ends ................................................ 17
Electrical System - General............................. 19
Glow Plugs....................................................... 18
Booster Batteries.............................................. 18
Battery Care..................................................... 18
Winterizing / Out-of-Service ........................... 18
AC GENERATOR - TF-276M/ TF-276D
General............................................................. 19
Connections ..................................................... 20
Operation ......................................................... 21
Maintenance............................................. 21 - 22
TROUBLESHOOTING
Electrical.......................................................... 23
Engine...................................................... 24 - 26
DATA SHEETS
Marine...................................................... 27 - 28
WIRING DIAGRAMS
DC Electrical ................................................... 29
AC Electrical ........................................... 30 - 32
Proprietary Information
This publication is the property of Northern Lights, Inc.
It may not be reproduced in whole or in part without the written permission of Northern Lights, Inc.
© Northern Lights, Inc. All rights reserved. Litho U.S.A. Publication number OM673 09/09
Table of Contents
1

OM673 09/09
The servicing of marine engines and generator sets
presents unique problems. In many cases boats
cannot be moved to a repair facility. Marine engines
cannot be compared to the servicing of automo-
biles, trucks or even farm equipment. Failures often
occur in remote areas far from competent assistance.
Marine engines are taxed far more severely than
auto or truck engines; therefore, maintenance
schedules must be adhered to more strictly.
Failures begin with minor problems that are
overlooked and become amplified when not corrected
during routine maintenance.
As operator, it is your obligation to learn about your
equipment and its proper maintenance. This is not a
comprehensive technical service manual. Nor will it
make the reader into an expert mechanic. Its aim is to
aid you in maintaining your unit properly.
Introduction
M - Northern Lights marine generator set Model number of engine block
Bore Cylinders
67 mm 3
Serial Numbers
MODELS INCLUDED
This manual covers the operating instructions for:
M673M, M673L, and M673D marine generator sets.
Model Numbers
Model numbers give the unit's application, block model, aspiration, and RPM:
+
Unit Identification
Northern Lights marine diesel generator set with a 673 engine, TF-276M generator end,
and an automatic voltage regulator.
Northern Lights marine diesel generator set with a 673 engine, TF-276D generator end,
and an automatic voltage regulator.
Northern Lights marine diesel generator set with a 673 engine, TF-276D generator end,
and an automatic voltage regulator.
M673M
M673L
M 673
=
=
Your set has three serial numbers: 1 an engine number stamped
on the block, 2a generator number, and 3a generator set number.
Use the serial number on the generator set data plate when ordering
parts or in correspondence. The generator set data plate is found on
the service side of the generator and resembles the drawing in
Figure 1.
Figure 1: Generator set serial number data plate.
2
M673D =
AC Generator Data
Generator Set Data
Northern Lights, Inc., WA USA
www.northern-lights.com
Model No.
Serial No.
DUTY
KW
KVA
RPM
HERTZ
PHASE
°C RISE
RULE
WIRE
INSUL
AMB°C
PF
VOLTS
VOLTS
AMPS
AMPS
Set Serial
Set Model

OM673 09/09
CAUTION: This symbol is used throughout
this book to alert you to possible danger areas.
Please take special notice of these sections.
A warranty registration certificate is supplied
with your set. It entitles the original purchaser of
our equipment to a warranty covering material
or assembly faults. The extent of coverage is
described in the Limited Warranty Statement. We
recommend that you study the statement carefully.
NOTE: If the warranty is to apply, the servicing
instructions outlined in this manual must be
followed. If further information is needed, please
contact an authorized dealer or the factory.
CAUTION: Accident reports show that careless use of engines causes a high percentage of accidents.
You can avoid accidents by observing these safety rules. Study these rules carefully and enforce them on the job.
• Use caution in handling fuel. Never refuel a hot
or running engine. Do not smoke while filling
fuel tank or servicing fuel system.
• Keep your hands, feet, hair and clothing away
from power-driven parts.
• Check for any loose electrical connections or
faulty wiring.
• Engines should be operated only by knowledge-
able, qualified personnel.
• Look completely around engine to make sure
that everything is clear before starting.
• Do not operate an engine that isn't in proper work-
ing order. If an unsafe operating condition is noted,
tag the set and control panel so others will also
know about the problem.
• Provide first aid kits.
• Never leave engine without proper security.
• Turn the coolant tank cap slowly to relieve
pressure before removing. Add coolant only
when the engine is stopped and cool.
• Mount a fire extinguisher near engine.
• Always disconnect the battery ground strap
before making adjustments.
• Operate engines in properly ventilated areas.
• Keep trash and other objects away from engine.
• Escaping fluids under pressure can penetrate
your skin. Use a piece of cardboard or wood,
not your hands, to search for leaks.
• Avoid wearing loose clothing without a belt
when working around engines.
• Do not oil or grease engine while it is running.
Safety Rules
Warranty
3

OM673 09/09
1. Heat Exchanger End Cap
2. Coolant Fill
3. Heat Exchanger/Expansion
Tank/Exhaust Manifold
4. Lube Oil Fill- Top
5. Wet Exhaust Elbow
6. Generator End Cover
7. Base and Drip Pan
15. Air Filter Housing
16. Fuel Injector
17. Fuel Injection Pump
18. Fuel Lift Pump
19. Lube Oil Drain
20. Sea Water Pump
21. Lube Oil Fill- Side
8. Starter Motor
9. DC Regulator
10. Belt Guard
11. DC Alternator
12. DC Circuit Breaker
13. Generator Control Box
14. AC Circuit Breaker
22. Lube Oil Dipstick
23. Block Drain
24. Lube Oil Filter
25. Secondary Fuel Filter
26. Control Panel Plug-In
27. Fuel Inlet and Return
28. AVR Circuit Breaker
Marine Generator Component Locations
4
Figure 2: M673 Non-Service Side.
Figure 3: M673 Service Side.

OM673 09/09
Figure 6-B: Series 3 Generator Control Panel
Control Panels
Figure 6-A: Series 1-B Generator Control Panel
Figure 6-C: Series 4 Generator Control Panel
5
1. SHUTDOWN BYPASS-PREHEAT SWITCH
There are three functions built into this switch:
preheating the engine, flashing the generator field, and
bypassing the engine safety shutdown circuit enabling
a start. Hold the switch in the ON position for approxi-
mately 10 to 20 seconds before starting a cold engine.
Holding the switch ON for too long can burn out the
glow plugs.
NOTE: Three position Engine Control switches must be
in the RUN position during preheating. Preheat switch
must be held in ON position during starting.
2. ENGINE CONTROL SWITCH
To start the engine, hold this switch in the START posi-
tion until the engine is running.
NOTE: Excessive cranking of marine sets equipped
with water lift muffler systems can cause engine
damage. See page 7.
After the engine starts, release the switch and it will
return to RUN position. To stop the engine, hold the
switch in the STOP position.
NOTE: The rocker switch is used on Series 1 panels
only, and has a light that glows when the set is running.
3. HOUR METER
Keeps track of engine running time.
4. OIL PRESSURE GAUGE
Shows the oil pressure in the engine lubricating system.
5. WATER TEMPERATURE GAUGE
Registers the temperature of the cooling water.
6. D.C. VOLTMETER OR AMMETER
When the engine is stopped, the voltmeter indicates the
condition of the battery. When the engine is running, the
voltmeter indicates the voltage output of the alternator.
For Series 4 Control Panels Only:
7. A.C. VOLTMETER
Shows the generator output voltage.
8. FREQUENCY METER (Hertz)
The frequency meter indicates engine speed: 1200 or
1800 RPM (60 Hz), or 1500 RPM (50 Hz).
9. AMMETER SELECTOR SWITCH
Used to check each phase for load condition.
NOTE: Always leave this switch in the ON position
while the unit is running.
10. A.C. AMMETER
Shows the generator load on each phase. The phase is
selected with the Ammeter Selector switch (Item 9).

OM673 09/09
Control Panels
6
Figure 7-A: Series 7.1 through Series 7.6 Generator
Control Panels.
Figure 7-B: Status Indicators for Series 7.3 through
Series 7.6 Generator Control Panels.
1. SHUTDOWN BYPASS SWITCH
Manual Start Panels
(S-7.0 and S-7.3)
Hold the switch in the on position for approximately
10 to 20 seconds before starting a cold engine. Hold-
ing the switch on for too long can burn out the glow
plugs. To start the engine the bypass switch must be
held on while moving the engine control switch into
the start position. As soon as the engine starts release
both switches.
Auto Start Panels
(S-7.2, S-7.4, S-7.5, and S-7.6)
When the switch is in the auto start position, the unit
will start upon closure of auxillary contacts. Moving
the switch to the manual position will start the engine
and it will run after the control timers have completed
their sequence.
2. OIL PRESSURE GAUGE
Shows the oil pressure in the engine lubricating system.
3. HOUR METER
Keeps track of engine running time.
4. ENGINE TEMPERATURE GAUGE
Registers the temperature of the coolant.
5. D.C. VOLTMETER
When the engine is running, the voltmeter indicates the
voltage output of the alternator.
6. STATUS INDICATOR PANEL
Engine monitoring alarms and lamps for monitoring
engine functions.
7. ALARM LAMP TEST AND RESET BUTTON
Press UP to test the indicator lights and press DOWN
to reset the alarm.
8. A.C. VOLTAGE ADJUSTMENT RHEOSTAT
Voltage has been set at the factory and should only be
adjusted by factory-trained personnel.
9. AMMETER SELECTOR SWITCH
Used to check each phase for load condition.
NOTE: Always leave this switch in the ON position
while the unit is running.
10. FREQUENCY METER (HERTZ)
The frequency meter indicates alternator current fre-
quency: 60 Hz (1200 or 1800 RPM), or 50 Hz (1500
RPM).
11. A.C. VOLTMETER
Shows the generator output voltage.
12. A.C. AMMETER
Shows the generator load on each phase. The phase is
selected with the Ammeter Selector switch (Item 9).

OM673 09/09
BREAK-IN PERIOD
1. The first 100 hours on a new or reconditioned
engine are critical to its life and performance.
2. Constantly check the engine temperature and oil
pressure gauges (sets with Series 3 or 4 panels).
3. Oil consumption is greater during break-in as
piston rings take time to seat.
4. Break-In Oil Changes: Change engine oil and
filter at 50 hours. Change oil and filter again at
100 hours (consult Lubricants section for oil recom-
mendation).
Operating Instructions:
Maintain at least a 75% load on your generator
set for the first 100 hours. Vary the load will help
seat the rings.
BEFORE STARTING
1. Check the water level by removing the pressure
cap from the expansion tank or radiator. In order to
give the cooling water an opportunity to expand, the
level should be about 1 in. (2.5 cm) below the filler
cap sealing surface when the engine is cold.
CAUTION: Use protective clothing and open the
filler cap carefully when the engine is warm to
prevent burns.
2. Check the oil level in the crankcase with the dip-
stick. The oil level must be in the waffled area on the
stick. Never allow the level to go below this area.
Always add the same viscosity of oil as is already in
the crankcase.
3. Check the fuel tank level and open any fuel valves.
4. Marine Sets: close the sea-cock, check and clean the
sea strainer and reopen the sea-cock.
5. Marine Sets: place the battery switch in the ON posi-
tion.
NOTE: The battery switch must always be kept
ON while the engine is running. If the switch is
turned OFF while the engine is running, the bat-
tery charging regulator could be ruined.
STARTING FOR S-1, S-1B, S-3, AND S-4, SEE
PAGE 6 FOR S-7
1. Hold the Shutdown Bypass-Preheat switch in the ON
position for 10 to 20 seconds before starting a cold
engine. Holding the switch too long can burn out the
glow plugs.
2. While holding the Shutdown Bypass-Preheat switch
in the ON position, push the Engine Control switch
to the START position.
3. As soon as the engine starts, release both switches.
Do not crank the starter for more than 20 seconds
consecutively. If the engine fails to start with the
first attempt, be sure that it has stopped completely
before re-engaging.
NOTE: Excessive cranking of the starter on Marine
sets equipped with a water lift muffler can cause
engine damage. If the engine does not start after
three 20-second cranks, remove the impeller from the
raw water pump. This will prevent the muffler from
filling with water and backfilling the exhaust line and
engine. Once the engine starts, shut it off immedi-
ately and re-install the impeller. Re-start the engine
and check the exhaust overboard outlet for gushes of
water.
OPERATING
1. Units with Series 3, Series 4, and Series 7 Control
Panels: check gauges often. Oil pressure must be above
15 PSI. The D.C. voltmeter should read between 11
and 15 volts at 80°F (25°C) ambient temperature.
The water temperature gauge on Marine sets must be
below 200°F (94°C); on Industrial units, the water
temperature gauge must be below 225°F (107°C).
Check the A.C. voltage and frequency meters (Series 4
and 6 panels). If the gauges deviate from normal levels,
shut down the generator set and investigate.
2. Let the unit run unloaded for a 3 - 5 minute warm-up
period.
3. Add electrical load.
STOPPING
1. Remove electrical load from the generator set.
2. Run the engine for a 3 to 5 minute cool down period.
2. Move the Engine Control switch to the STOP posi-
tion momentarily.
3. Marine Sets: shut off the seacock, fuel valve, and
battery switch.
Operating Procedures
7

OM673 09/09
Operating Procedures
8
SHUTDOWNS AND ALARMS
1. Your unit may be fitted with a warning horn to
protect it from high water temperature or low oil
pressure.
a. Generator sets have shutdown systems to stop the
engine. They have no warning horns.
b. Other alarms and shutdowns are available as
optional equipment.
NOTE: Do not rely on your warning to the exclu-
sion of careful gauge monitoring. Watching your
gauges can prevent damage to the unit and danger-
ous power losses.
2. Do the following when your warning or shutdown
system is activated:
a. Check the temperature gauge.
If above 205°F (96°C), shut off the
engine immediately.
b. Use the Trouble Shooting Guide on page 25 to
isolate the cause of the overheat.
CAUTION: Do not remove the water fill
cap of an overheated engine. Escaping high
temperature steam can cause severe burns. Allow
the engine to cool and then remove the cap slowly
using protective clothing.
c. Make repairs. Restart your Marine set after the
temperature gauge registers below 200°F (94°C).
d. Watch the temperature gauge regularly and
turn off the unit if the temperature rises above
205°F (96°C) on Marine units.
3. If shutdown is activated and the temperature gauge
shows temperature within normal temperature range:
a. Check the engine crankcase oil level.
b. If the oil level is low, fill with recommended
lubricating oil and restart. Watch the oil pressure
gauge carefully and shut off the engine if it does
not show a normal reading (20-60 PSI) after a
few seconds of operation.
c. If the oil level is normal, DO NOT restart the
engine. Call your dealer for assistance.
SPARE PARTS
1. ADE recommends that you keep the following spare
parts on hand for field service. The parts are
available from your local Northern Lights dealer.
Some marine models already have “On-Board-Kits,”
a handy box that contains the most common parts
you will need.
2. All owners should have the following:
a. Primary and secondary fuel filter elements
b. Oil filters
c. Air filter (industrial units only)
d. Alternator belt
e. Thermostat and gaskets
f. Raw water pump impeller & gaskets (marine only)
f. Glow plug
g. Injector and washer
3. If your set is operating a long distance from a servic-
ing dealer, add the following:
a. Complete set of injectors
b. Copper washers for injector change
c. Complete set of glow plugs
d. Fuel lift pump

OM673 09/09
SERVICE 50 250 500 1000 2500
POINT PAGE OPERATION DAILY Hours Hours Hours Hours Hours
ENGINE:
SP1 11 Check oil level •
SP2 11 Change engine oil 1) 5) ••
SP3 11 Change lube oil filters 1) 5) ••
SP4 12 Check air cleaner 1) 4) 5) 6) •
SP5 12 Check V-belt tension 1) 4) •
SP6 12 Check valve clearances 1) 2) •
FUEL SYSTEM:
SP7 13 Check primary filter (Racor) 2) 3) •
SP8 13 Change primary filter element (Racor) 2) 3) •
SP9 13 Change secondary fuel filter 1) 3) •
SP10 14 Bleed the fuel system 3)
SP11 15-16 Check injectors 1) 3) •
SP12 15 Check fuel injection pump •
COOLING SYSTEM:
SP13 15 Check cooling water level •
SP14 17 Check and flush cooling system 1) •
SP15 17 Check and clean heat exchanger •
SP16 17 Change impeller in raw water pump 1) 3) •
SP21 Inspect condition of exhaust elbow 1) 4) •
ELECTRICAL SYSTEM:
SP17 18 Check electrolyte level in batteries 1) 4) •
SP18 18 Check condition of batteries with hydrometer 1) 4) •
OUT OF SERVICE:
SP20 18 Winterizing or out-of-service 3)
The Servicing Schedule Chart below shows the service schedule required for proper maintenance of your generator
set. More detailed coverage of each Service Point (SP) is listed on the page noted in the ‘page’column.
DAILY:
SP1 Check oil level in engine
SP5 Check V-belt tension
SP7 Check primary fuel filter
SP13 Check cooling water level
Check sea strainer
SP17 Check electrolyte level in batteries
AFTER FIRST 50 HOURS:
SP2/3 Change engine oil and filter
SP6 Adjust valves
AFTER FIRST 100 HOURS:
SP2/3 Change engine oil and filter
EVERY 250 HOURS:
SP2/3 Change engine oil and filter
SP4 Check air cleaner
SP10 Bleed the fuel system
SP18 Check condition of batteries with a hydrometer
EVERY 500 HOURS:
SP8 Change primary fuel filter element
SP9 Change secondary fuel filter
SP21 Inspect condition of exhaust elbow
EVERY 1000 HOURS:
SP4 Change air cleaner element
SP6 Check valve clearances
SP11 Check injectors
SP16 Change impeller
EVERY 2500 HOURS:
SP12 Check fuel injection pump
SP14 Check and flush cooling system
SP15 Check and clean heat exchanger
1) Perform all maintenance once a year even if hour level has not been reached.
2) Consult manufacturer's maintenance schedule, note on chart.
3) Whenever necessary.
4) More often if necessary.
5) After first 50 hours, and again after first 100 hours, then every
250 hours.
6) Change air cleaner element at 1000 hours.
Servicing Schedule Chart
9

OM673 09/09
Notes
10

OM673 09/09
Servicing
LUBRICATION - GENERAL
1. Use only clean, high quality lubricants stored in
clean containers in a protected area.
2. These lubricants are acceptable:
a. API Service CC/CD/CE single viscosity oils.
b. API Service CC/CD/SF multi-viscosity oils.
3. Use the proper weight oil for your average operation
temperature.
Figure 8: Lube Oils
4. Some increase in oil consumption may be expected
when SAE 5W and SAE 5-20W oils are used. Check
oil level frequently.
5. Never put additives or flushing oil in crankcase.
SP1. CHECKING OIL LEVEL
1. Check the oil level in the crankcase with the dip-
stick. The oil level must be in the waffled area
on the stick. Never allow the level to go below this
area. Follow the lubrication recommendations above.
SP2. OIL CHANGES
1. The set is delivered with special break-in oil.
Change the engine oil and oil filter after 50 hours
of operation. Use Service CC 30 weight oil during
the first 100 hours.
2. Change the oil and filter again at 100 hours using
the oil recommended in the previous diagram. After
this, change oil and filter on marine units every 250
hours.
3. During intermittent cold weather operation, change
oil every 100 hours or six weeks, whichever comes
first.
4. Change oil at any seasonal change in temperature
when a new viscosity of oil is required.
5. Change oil when engine is warm.
6. Dispose of waste oil in an approved manner.
7. Never use a flushing oil.
8. Loosen the clamp on the oil change tube. Remove
cap. Drain oil. Replace the cap and tube.
9. Refill engine with recommended oil.
10. Engine capacity with new oil filter is:
673M, D, & L – 3.2 quarts (3.0 liters)
SP3. CHANGING LUBE OIL FILTER
1. Change the lube oil filter every with every oil
change.
2. Use a filter wrench to remove old filter. Dispose of
filter in approved manner.
3. Make sure the gasket from the old filter is removed
and discarded. Clean mount face.
4. Spread a thin film of engine oil on the rubber gasket
on the new filter and screw it on nipple until gasket
meets the sealing surface.
5. Using hands only – no wrench – tighten filter
one-half turn farther. Overtightening can do
damage to filter housing.
6. Fill engine with recommended oil. Start engine and
check for leakage. Stop engine, wait 3 minutes, and
check oil level. Add additional oil if necessary.
7. Oil filter part numbers are:
673M – #24-02001
673L – #24-08001
Air Single Multi-
Temperature Viscosity Viscosity
Above 32°F SAE 30W SAE 15-40W
(0°C)
-10 to 32°F SAE 10W SAE 10-30W
(-23 to 0°C)
Below -10°F SAE 5W SAE 5-20W
(-23°C)
11

OM673 09/09
Servicing
12
SP4. AIR CLEANER
1. Inspect air cleaner every 250 hours. In dusty condi-
tions, check more often.
2. M673:
Inspect the element. If it is dirty, wash the element
in soapy water. Rinse and dry thoroughly before re-
installing.
NOTE: Make absolutely sure no impurities enter
the engine while changing the element. Do NOT
run the engine with the air cleaner removed.
SP5. V-BELTS
1. Check the tension and wear on the V-belt
daily.
2. Use your thumb to press on the belt at the midpoint
between the crankshaft and alternator pulleys. The
tension is correct if the belt can be depressed about
3/16 in. (5 mm).
TORQUING CYLINDER HEAD BOLTS
1. Tighten bolts when the engine is cold.
2. Loosen the nuts and remove rocker arm cover.
3. Remove fuel injectors and related tubes.
4. Tighten head bolts with a torque wrench in the order
shown in the figure below. Tighten bolts evenly in 2 or
3 passes, ending at the specified torque in final pass.
a. Torque: 26 - 29 ft/lbs (3.5 - 4.0 kg/m)
5. Re-install rocker arm shaft and adjust valves.
Torque nuts to: 7 - 9 ft/lbs (1.0 - 1.3 kg/m)
6. Re-install injectors and tubes and rocker cover.
Torque injectors to: 43 - 51 ft/lbs (6 - 7 kg/m)
Use new injector sealing washers.
Figure 9: 673M Head Torque Sequence
Figure 10: Valve Adjustment
SP6. VALVE CLEARANCES
1. Re-adjust valve clearance after first 50 hours of
operation and every 1000 hours thereafter.
2. Valve adjustments should be done after the cylinder
head bolts have been re-tightened. Engine should be
cold and NOT running.
3. Watch the valves while turning the engine over by
hand. Turn until the #1 cylinder inlet valve starts to
open and the exhaust valve starts to close (the valves
are rocking). Then turn the crankshaft one more full
turn and adjust the clearance on both valves for this
cylinder.
4. Loosen the lock nut and adjust the clearance between
the rocker arm and valve stem of both the intake and
exhaust valves with the adjustment screw (Figure
10). Clearance on both intake and exhaust valves
should be 0.008 in. (0.2 mm).
5. Repeat steps 3 and 4 for each cylinder. Each set of
valves must be adjusted individually.
6. Replace the rocker arm cover. Tighten cover nuts to
7.2 - 8.7 ft/lbs (1.0 - 1.2 kg/m).

OM673 09/09
Servicing
13
FUELS - GENERAL
1. Use only clean, high quality fuels of the following
specifications, as defined by ASTM designation
D975 for diesel fuels:
a. Use Grade No. 2 diesel at ambient temperatures
above freezing 32°F (0°C).
b. Use Grade No. 1 at ambient temperatures below
freezing and for all temperatures at an altitude of
above 5,500 ft. (1500 meters).
2. Use fuel having less than 1% sulphur (preferably
less than 0.5%).
3. The cetane number should be a minimum of 45.
4. DO NOT use these unsuitable grades of fuel:
a. Domestic heating oils, all types.
b. Class B engine.
c. Class D domestic fuels.
d. Class E, F, G or H industrial or marine fuels.
e. ASTM-D975-60T No. 4-D and higher number
fuels.
5. Storing fuel:
a. Keep dirt, scale, water, and other foreign matter
out of fuel.
b. Avoid storing fuel for long periods of time.
c. Fill the fuel tank at the end of each day’s
operation. This will reduce condensation.
SP7-9. FUEL FILTERS
1. Your generator set should have a primary fuel filter
installed. We recommend the Racor brand of fuel
filter-water separators.
a. Check the primary fuel filter daily as
recommended by the filter manufacturer.
Empty the collection bowl as necessary.
b. Change the element as often as necessary or
every 250 hours.
c. If the bowl fills with water, change the primary
and secondary element immediately.
2. Change secondary fuel filter every 200 hours.
a. Remove the spin-on filter by turning it
counterclockwise with a filter wrench. Fill the
new cartridge with fuel and install it after
applying engine oil to gasket surface. Screw on
until the gasket surface comes into contact with
sealing surface of filter base. Then, tighten it
two-thirds of a turn by hand. Do not overtighten.
b. Fuel filter part numbers are:
#24-52020
Found on all M673M, D, & L units

OM673 09/09
Servicing
Figure 11-A: M673 Fuel System.
SP10. BLEEDING THE FUEL SYSTEM
CAUTION: Escaping diesel fuel under pressure
can penetrate skin causing serious personal
injury. Before disconnecting lines be sure to
relieve all pressure. Before applying pressure,
be sure all connections are tight and lines,
pipes and hoses aren't damaged. Fuel escaping
from a very small hole can be almost invisible.
Use a piece of cardboard or wood, rather than
hands, to search for suspected leaks. If injured
by escaping fuel, see a doctor at once. Serious
infection or reaction can develop if proper medi-
cal treatment isn't administered immediately.
1. The fuel system is self-bleeding. However, any
system may need manual bleeding when:
a. A new fuel filter is installed;
b. The engine has run out of fuel;
c. The fuel lines, injection pump or any other fuel
system component has been removed and installed.
2. Loosen bleed screw “A” (Figure 11) on top of the
filter. Pump hand primer “B” on fuel lift pump until
pure fuel (no bubbles) escapes from bleed screw
“A”. Tighten bleed screw “A”.
3. Loosen bleed screw “C”. Pump hand primer “B” on
fuel lift pump until pure fuel (no bubbles) escapes
from bleed screw “A”.
4. If the engine does not start after the above bleeding
process, loosen a fuel line at the injector. Crank the
engine until fuel escapes, then tighten the connec-
tion. Do each line one at a time.
5. After the engine has started, check for fuel leaks.
14

OM673 09/09
Servicing
15
SP11. INJECTOR SERVICE
1. Injectors should be checked every 600 hours. Check
should be made by a Northern Lights dealer or local
injection repair station.
CAUTION: Escaping diesel fuel under pressure
can have sufficient force to penetrate the skin
causing serious personal injury. If injured by
escaping diesel fuel, see a doctor at once.
2. Injector removal:
a. Clean loose dirt from around the injectors and
the fuel lines.
b. Relieve high pressure in the fuel lines by
loosening the delivery line flare nuts at each
injector (Figure 12).
c. Remove delivery lines by disconnecting from
injectors and injection pump (Figure 13). Remove
all lines as an assembly; do not remove the
clamp. Cover the ends of the lines, the injector
inlets and injection pump outlets to keep dirt out
(Figure 14).
d. Remove the return line retaining bolts (Figure 15).
Remove the return line (Figure 16).
e. Unscrew and remove the injectors (Figure 17).
NOTE: Do not use pry bars to remove injectors
from cylinder head.
f. After removing the injectors, discard the copper
sealing washers from the injector hole in the head
(Figure 18). Cover holes to prevent dirt and debris
from entering the cylinders.
3. Injector installation:
a. Install a new copper sealing washer in each
injector hole (Figure 18).
b. Screw in injector and tighten to 43 or 50 ft/lbs
(6 to 7 kgm) (Figure 19).
NOTE: Overtightening can damage injector.
c. Installreturnlineusingnewcoppersealingbelow
each connection. Tighten return line retaining
bolts to 22 - 30 ft/lbs.
d. Install delivery lines. Leave loose at injectors for
bleeding.
e. Crank the engine to fill lines. Tighten lines at
injectors.Startengineandcheckforleaksusinga
piece of paper or cardboard.
DO NOT use hand to check for leaks.
SP12. INJECTION PUMP
1. Since operating conditions may vary considerably, it
is difficult to give a definite interval for checking the
injection pump. But as a rule, pump settings, maxi-
mum speed, idle speed and exhaust smoke should be
checked after every 2400 hours of operation. Service
of the fuel injection pump should only be done if
checks indicate pump malfunction.
2. Black smoke can be an indication of pump
malfunction. Before servicing the pump, check other
possible causes:
a. Check cleanliness of air filter.
b. Check valve clearances.
c. Clean and check injectors.
3. Any repair which involves disassembly of the injec-
tion pump must be carried out by specially trained
mechanics with the proper tools and test equipment.
NOTE: All warranties on the engine become null
and void if the injection pump seals are broken by
unauthorized persons.
COOLING SYSTEM - GENERAL
NOTE: Marine sets – be sure to close the sea-cock
before working on the engine cooling system.
CAUTION: The cooling water in the engine
reaches extremely high temperatures. You must
use extreme caution when working on hot
engines to avoid burns. Allow the engine to cool
before working on the cooling system. Open the
filler cap carefully, using protective clothing
when the engine is warm.
SP13. CHECK THE COOLANT LEVEL
1. Check the coolant level each day before starting the
engine. Check the water level by removing the pres-
sure cap from the expansion tank or radiator.
In order to give the cooling water an opportunity to
expand, the level should be about 1 in. (2.5 cm) below
the filler cap sealing surface when the engine is cold.
2. The pressure valve in the filler cap releases when the
pressure is approximately 7 PSI (0.5 bar). Use a cap
pressure tester to check cap if you suspect it is faulty.

OM673 09/09
Servicing
16
Figure 12: Remove delivery line flare nuts.
Figure 13: Remove delivery lines.
Figure 14: Cover lines, inlets and injection pump outlets.
Figure 15: Remove return line nuts.
Figure 17: Unscrew injector.
Figure 18: Remove and replace copper sealing washer.
Figure 19: Reinstall injector. Torque to proper tightness.
Figure 16: Remove return line.

OM673 09/09
Servicing
SP14. COOLING SYSTEM FLUSHING
1. Flush the cooling system every 600 hours or every
12 months, whichever comes first.
2. Marine sets:
a. Remove expansion tank cap and drain engine
block.
b. Leave all drains open.
c. Pour clean water into expansion tank until water
coming from drains is free of discoloration and
sediment.
d. Let water drain completely.
e. Close drains and refill with recommended
mixture.
NOTE: Open sea cock before running engine.
3. Industrial sets:
a. Remove radiator cap and open drain cocks on
radiator and engine block.
b. Pour clean water into radiator until water coming
from radiator is clear of discoloration.
c. Close the radiator drain and continue flushing until
water from engine drain is clear.
d. Open all drain cocks and drain completely.
e. Close drain cock and refill with recommended
coolant mixture.
f. Clean fins on radiator.
4. Coolant Specifications (marine and industrial):
Use 50% water / 50% ethylene glycol antifreeze
mix. Antifreeze mixture is recommended as a good
year-round coolant.
5. Check hoses and connections and repair any leakage.
SP15. HEAT EXCHANGER
1. Clean the heat exchanger core once a year or after
2400 hours of operation.
2. Drain expansion tank and heat exchanger.
3. Remove heat exchanger end covers and remove
core.
4. Clean the inside of exchanger core tubes using
a metal rod. Flush, inspect and clean again if neces-
sary.
5. Reassemble. Fill the cooling system, start the engine
and check for leaks.
SP16. RAW WATER PUMP
1. Change the seawater pump impeller every 1000
hours, or as needed.
2. Remove the pump end cover. Pry out the impeller
using needle-nose pliers or two screwdrivers.
Be sure you remove all pieces of failed impeller.
NOTE: Place some kind of protection under the
screwdrivers in order not to damage the pump
housing.
3. Clean the inside of the housing.
4. Press in the new impeller and place the sealing
washers in the outer end of the impeller center if this
has not already been done.
5. Replace the cover using a new gasket or o-ring.
NOTE: Make sure that there is always an extra
impeller and cover gasket in reserve on board.
GENERATOR ENDS
The maintenance and operation recommendations
for the generator end are located on pages 19-22
under the heading “AC Generator”.
ELECTRICAL SYSTEM - GENERAL
1. Never switch battery switch off or break the circuit
between the alternator and batteries while the engine
is running. Regulator damage can result.
2. Do NOT reverse the polarity of battery cables when
installing the battery.
3. When welding on the unit, disconnect the AC and
DC voltage regulator and battery. Isolate the leads.
4. Disconnect the battery cables when servicing the
D.C. alternator.
5. Never test with a screwdriver, etc., against any ter-
minal to see if it emits sparks.
6. Do not polarize the alternator or regulator.
7. A D.C. circuit breaker protects your control panel
and wiring harness. It is located in the side of the
generator junction box.
17

OM673 09/09
GLOW PLUGS
1. Each cylinder is supplied with a glow plug which
serves to heat the combustion chamber for starting.
2. To check the glow plugs, loosen the current
carrying flat wire between the plus-poles of the
glow plugs (Figure 20). Connect a D.C. test bulb
between the plus-pole of the battery and the
plus-pole of the glow plug. If the bulb lights up,
the glow plug is functioning properly.
3. Check all glow plugs and replace any faulty ones.
Figure 20: Glow plugs.
BOOSTER BATTERIES
CAUTION: Battery gas can explode.
Keep all flames and sparks away from batteries.
1. Before changing or using booster batteries, check bat-
tery electrolyte level. Add distilled water if necessary.
2. Booster and main batteries must have the same volt-
age rating.
3. First, connect positive (+) terminal of booster bat-
tery to positive (+) terminal of main battery. Then,
connect negative (-) terminal of booster battery to
ground on the engine block (see Figure 21).
4. Remove booster battery after starting engine.
5. Sealed batteries: See manufacturer charging and
booster instructions.
SP 17-18. BATTERY CARE
1. Check electrolyte level every 50 hours or once per
month. Add distilled water to manufacturer’s
recommended level.
2. Batteries, cables and cable terminals should
be checked and cleaned every 100 hours.
Clean corrosion with a water and baking soda solu-
tion. Flush with clean water. Tighten terminals and
grease them to inhibit corrosion.
3. Check the battery condition with a hydrometer every
600 hours.
SP19. WINTERIZING / OUT-OF-SERVICE
1. Drain fresh water and seawater cooling systems
completely. Remember to shut off seacocks
before opening drain cocks if the vessel is in the
water.
2. Drain water supply lines and wet exhaust line.
3. Loosen the seawater pump cover and drain pump.
4. Change the crankcase oil and filter.
5. Loosen the alternator belt.
6. Disconnect and clean battery. Remove to warm
storage place if possible.
7. Clean outside of unit. Paint any scratched or
chipped surfaces. Put corrosion preventative on
all exposed metal surfaces.
8. Fill the fuel tank or add biocide as per
manufacturer’s instructions.
18
Figure 21:
Battery connections.
Servicing