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Northern Lights L673L Engine

The Northern Lights L673L is a 0.76 L 3-cylinder naturally aspirated engine rated at 1800 rpm, producing up to 7.38 kW. It powers generator sets from Northern Lights, including the M673 and NL673. It holds 3.1 L (0.8 gal) of oil.

Also known as: Lugger L673L Engine

Part of the Northern Lights 673 engine family — 4 variants share parts & fitment.

0.76 L

Displacement

Cylinders

1800 rpm

Rated speed

7 kW

Gross power

On this pageSpecs Generator sets Maintenance FAQ Service intervals Torque & specs Fluids Fault codes Procedures Wiring

Engine specifications

Oil capacity	3.1 L
Displacement	0.76 L
Cylinders	3
Aspiration	Naturally Aspirated
Rated speed	1800 rpm
Gross power	7 kW

Generator sets powered by this engine

Northern Lights M673 Northern Lights NL673

How to read your Northern Lights engine serial & model number →

Common problems

Engine Hard to Start or Will Not Start
Cause: Improper starting procedure
Fix: See starting section of this manual. Take special note of Bypass Switch operation
Engine Runs Irregularly or Stalls Frequently
Cause: Below normal engine temperature
Fix: Remove and check thermostat
Lack of Engine Power
Cause: Intake air restriction
Fix: Service air cleaner
Starter Inoperative
Cause: DC circuit breaker tripped
Fix: If the breaker is tripped, reset it
Starter Cranks Slowly
Cause: Low battery output
Fix: Battery is too small; Battery cables are too small
Entire Electrical System Does Not Function
Cause: DC circuit breaker tripped
Fix: If breaker is tripped, reset it
Battery Will Not Charge
Cause: Loose or corroded connections
Fix: Clean and tighten battery connections
High Fuel Consumption
Cause: Improper type of fuel
Fix: Use correct fuel for temperature.
Engine Overheats
Cause: Low coolant level
Fix: Fill tank or radiator to proper level; Check hoses for loose connections and leaks.
Engine Emits Black or Gray Exhaust smoke
Cause: Clogged or dirty air cleaner
Fix: Service air cleaner.
Engine Knocks
Cause: Insufficient oil
Fix: Call your dealer.
Engine Emits White Exhaust smoke
Cause: Improper fuel
Fix: Use correct fuel for temperature.
Low Oil Pressure
Cause: Low oil level
Fix: Fill crankcase to proper level.
High Oil Consumption
Cause: Break-in period
Fix: Oil consumption decreases after break in.
Below Normal Engine Temperature
Cause: Thermostats not working properly
Fix: Check thermostats.

Compiled from service & troubleshooting documentation across every generator set that uses the Northern Lights L673L.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Fuel filter	large spin-on fuel filter		24-52020	500 hr	Amazon eBay $24.71 NAPA $15.34
Oil filter	Full flow, spin-on oil filter with bypass		24-08001	250 hr	Amazon eBay $27.44 NAPA $9.09
Battery	Battery charging alternator with solid state voltage regulator and DC circuit breaker		—	50 hr
Belt			40-02002	50 hr	Amazon eBay $46.28
Oil	Trochoid oil pump	3.1 ltr	—	250 hr
Spark plug			—

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Service intervals

Item	Action	Hours	Months	Notes
Battery electrolyte	Check	50 hr	1 mo	First service — SP17; or once per month; daily per chart
Battery electrolyte level	Check	50 hr	1 mo	SP17; or once per month
Cylinder head bolts	Adjust	50 hr		First service — Retighten after first 50 hours when engine is cold
V-belt tension	Check	50 hr		First service — After first 50 hours and every 50 hours
valve clearances	Adjust	1000 hr		First service — SP6; after first 50 hours
valves	Adjust	50 hr		First service — After first 50 hours; adjust valves
Battery cables and terminals	Clean	100 hr		Clean and tighten every 100 hours
Battery, cables and terminals	Clean	100 hr
Engine oil and filter (industrial)	Change	100 hr		Every 100 hours industrial only
Radiator fins	Clean	100 hr		Remove debris daily; clean every 100 hours in dusty applications
batteries, cables, terminals	Clean	100 hr		SP18-19; check and clean every 100 hours
Air cleaner	Check	250 hr		Text: inspect every 250 hours; more often in dusty conditions
Engine oil and filter	Change	200 hr		First service — Text also states every 250 hours after the 100-hour change
Engine oil and filter (marine)	Change	200 hr		Every 200 hours marine only
Primary fuel filter element (Racor)	Change	500 hr		Text: every 250 hours or as necessary
Secondary fuel filter	Change	500 hr		Text: every 250 hours
primary fuel filter element	Change	200 hr		Servicing text SP7-9 states change as necessary or every 250 hours.
Batteries	Test	600 hr		Hydrometer check; SP18
Battery condition	Test	600 hr		With hydrometer
Fuel system	Other	250 hr		Bleed; SP10
Lube oil filter	Change	250 hr		First service — Every 250 hours; SP3
engine oil	Change	250 hr		First service — SP2; every 250 hours; with oil filter; perform yearly even if hours not reached
lube oil filters	Change	250 hr		First service — SP3; every 250 hours; perform yearly even if hours not reached
radiator filler cap	Check	250 hr		SP16; every 250 hours
Battery state of charge	Test	500 hr		With hydrometer
Exhaust elbow	Inspect	500 hr		SP21
Injectors	Check	1000 hr		Text: injectors checked every 1000 hours
cooling system	Clean	2500 hr	12 mo	Check and flush; servicing text SP14 states every 2500 hours or every 12 months, whichever comes first.
cooling system	Other	2500 hr	12 mo	SP14; check and flush every 500 hours per Servicing Schedule Chart
Battery state of charge (hydrometer)	Check	600 hr		Every 600 hours (SP19)
Cooling system	Check	600 hr	12 mo	Check and flush every 600 hours or every 12 months, whichever comes first (SP14)
Impeller in raw water pump (marine)	Change	600 hr		Every 600 hours or as needed (SP17)
Raw water pump impeller (marine)	Change	600 hr
Air cleaner element	Change	1000 hr		SP4
Air cleaner element	Check	1000 hr		SP4; possibly replace
Fuel injection pump	Check	2500 hr		Settings, max speed, idle speed and exhaust smoke checked every 2500 hours
Raw water pump impeller	Change	1000 hr		SP16
air cleaner element	Replace	1000 hr		Note 6: replace element every 1000 hours.
radiator	Clean	1000 hr		SP16; check and clean radiator every 1000 hours; remove debris daily; clean every 100 hours in very dusty applications
valve clearances	Check	1000 hr		SP6; every 1000 hours or as needed

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Service specifications

Type	Item	Value	Unit	Condition
Clearance	Coolant level below filler cap sealing surface	about 1	in. (2.5 cm)	engine cold
Clearance	V-belt deflection at midpoint between fan pulley and alternator pulley	3/16	in.
Gap	V-belt deflection	3/16	in.	at midpoint between crankshaft and alternator pulleys
Gap	V-belt deflection	5	mm	at midpoint between crankshaft and alternator pulleys
Gap	V-belt deflection at midpoint between crankshaft and alternator pulleys	3/16	in. (5 mm)
Other	Cooling water pH level	5.5 to 9.0	pH
Other	Engine oil capacity with new oil filter	3.3 quarts (3.1 liters)	quarts (liters)
Other	Maximum chlorides in cooling water	40	ppm (2.5 grains per gallon)
Other	Maximum dissolved solids in cooling water	340	ppm (20.0 grains per gallon)
Other	Maximum sulfates in cooling water	100	ppm (5.9 grains per gallon)
Other	Maximum total hardness in cooling water	170	ppm (10.0 grains per gallon)
Other	V-belt tension	3/16	in	deflection at midpoint between crankshaft and alternator pulleys
Other	V-belt tension	3/16 in (5 mm) deflection		midpoint between crankshaft and alternator pulleys
Pressure	Coolant filler cap release	0.5	bar
Pressure	Coolant filler cap release	7	PSI
Pressure	Coolant filler cap release pressure	7 PSI (0.5 bar)
Pressure	Cooling system filler cap release pressure	approximately 7	PSI (0.5 bar)
Pressure	Engine oil pressure (normal reading)	20-60	PSI	after a few seconds of operation
Pressure	Engine oil pressure minimum	above 15	PSI	operating
Pressure	Engine oil pressure normal	20-60	PSI	after a few seconds of operation
Pressure	Maximum exhaust back pressure	48	in H2O
Pressure	Minimum oil pressure	above 15	PSI	engine running
Pressure	Normal oil pressure	20-60	PSI	after a few seconds of operation
Pressure	Oil pressure	20 - 60 PSI		normal operation; minimum above 15 PSI
Pressure	Oil pressure	20-60	PSI	normal reading after a few seconds of operation
Pressure	Oil pressure	above 15	PSI	running
Pressure	Oil pressure minimum	15	PSI	operating
Pressure	Oil pressure normal	20-60	PSI	after a few seconds of operation
Pressure	Oil pressure normal reading	20-60	PSI	after a few seconds of operation
Pressure	Radiator filler cap pressure valve	7	PSI	approximately
Pressure	Radiator filler cap pressure valve release	7	PSI (0.5 bar)	approximately
Pressure	Radiator filler cap release pressure	approximately 7	PSI (0.5 bar)
Resistance	A-B resistance	0.25	ohm	at 20°C (68°F)
Resistance	AVR J-K resistance	16.6	ohm	at 20°C (68°F)
Resistance	Generator A-B resistance	0.25	ohm	at 20°C (68°F)
Resistance	Generator A-B resistance	0.25 ohm	ohm	at 20°C (68°F)
Resistance	Generator J-K resistance	16.6	ohm	at 20°C (68°F)
Resistance	Generator J-K resistance	16.6 ohm	ohm	at 20°C (68°F)
Resistance	Generator U1-V2 resistance	0.56	ohm	at 20°C (68°F)
Resistance	Generator U1-V2 resistance	0.56 ohm	ohm	at 20°C (68°F)
Resistance	J-K resistance	16.6	ohm	at 20°C (68°F)
Resistance	Resistance of A-B	0.25	ohm	at 20°C (68°F)
Resistance	Resistance of J-K	16.6	ohm	at 20°C (68°F)
Resistance	Resistance of U1-V2	0.56	ohm	at 20°C (68°F)
Resistance	U1-V2 resistance	0.56	ohm	at 20°C (68°F)
Speed	Rated speed	1800/1500	rpm	60 Hz / 50 Hz
Temperature	Battery warm before charging frozen battery	at least 16	°C (60°F)	frozen batteries
Temperature	Coolant restart threshold	below 225	°F	after overheating
Temperature	Coolant shutdown threshold	above 230	°F
Temperature	Coolant temperature	167°F to 194°F (75°C to 90°C)		normal operation; shutdown above 205°F (96°C)
Temperature	Coolant temperature shutdown point (industrial sets)	230	°F (110°C)	shut off engine immediately if above
Temperature	Coolant temperature to restart (industrial sets)	below 225	°F (107°C)
Temperature	Heat rise rating	95	°C	50°C ambient
Temperature	Industrial set normal water temperature (must be below)	225	°F (107°C)
Temperature	Industrial set water temperature shutdown limit	230	°F (110°C)
Temperature	Industrial shutdown temperature	230	°F	shut off immediately if above
Temperature	Industrial water temperature	107	°C	below
Temperature	Industrial water temperature	225	°F	below
Temperature	Industrial water temperature gauge	below 225	°F	operating
Temperature	Marine set normal water temperature (must be below)	200	°F (94°C)

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Recommended fluids

Fluid	Grade	Standard	Ambient	Capacity	Notes
Coolant	50% water / 50% ethylene glycol antifreeze			2.0 liters	Do not use methyl alcohol based antifreeze; avoid high silicate
Coolant	50% water / 50% ethylene glycol antifreeze mix				Recommended as a good year-round coolant; preferred water is distilled, deionized, soft water. Water quality limits: chlorides max 40 ppm/2.5 grains per gallon; sulfates max 100 ppm/5.9; dissolved solids max 340 ppm/20.0; total hardness max 170 ppm/10.0; pH 5.5 to 9.0.
Engine oil	API Service CC/CD/CE single viscosity oils; API Service CC/CD/SF multi-viscosity oils				Use proper weight oil for average operation temperature; never put additives or flushing oil in crankcase
Engine oil	SAE 30 weight Service CC			3.1 L (3.3 quarts)	Use during the first 100 hours; capacity with new oil filter
Engine oil	SAE 5-20W	API Service CC/CD/CE single viscosity or CC/CD/SF multi-viscosity	below -23°C	3.1 liters	Below -10°F (-23°C) multi-viscosity
Engine oil	SAE 5W	API Service CC/CD/CE single viscosity or CC/CD/SF multi-viscosity	below -23°C	3.1 liters	Below -10°F (-23°C)
Engine oil	SAE 5W (single viscosity) / SAE 5-20W (multi-viscosity)	API Service CC/CD/CE (single viscosity); API Service CC/CD/SF (multi-viscosity)	below -23°C		Below -10°F (-23°C); some increase in oil consumption may be expected
Engine oil	SAE 5W / SAE 5-20W	API Service CC/CD/CE single viscosity oils; API Service CC/CD/SF multi-viscosity oils	below -23°C		Below -10°F (-23°C)
Engine oil	SAE 5W single viscosity or SAE 5-20W multi-viscosity	API Service CC/CD/CE single; CC/CD/SF multi	below -23°C		Below -10°F (-23°C)
Engine oil	SAE 5W single viscosity; SAE 5-20W multi-viscosity	API Service CC/CD/CE or CC/CD/SF	below -23°C		Below -10°F (-23°C)
Engine oil	Service CC 30 weight	API Service CC			Use during the first 100 hours
Engine oil	SAE 10-30W	API Service CC/CD/CE single viscosity or CC/CD/SF multi-viscosity	-23°C to 0°C	3.1 liters	-10 to 32°F (-23 to 0°C) multi-viscosity
Engine oil	SAE 10W	API Service CC/CD/CE single viscosity or CC/CD/SF multi-viscosity	-23°C to 0°C	3.1 liters	-10 to 32°F (-23 to 0°C)
Engine oil	SAE 10W (single viscosity) / SAE 10-30W (multi-viscosity)	API Service CC/CD/CE (single viscosity); API Service CC/CD/SF (multi-viscosity)	-23°C to 0°C		-10 to 32°F (-23 to 0°C)
Engine oil	SAE 10W / SAE 10-30W	API Service CC/CD/CE single viscosity oils; API Service CC/CD/SF multi-viscosity oils	-23°C to 0°C		-10 to 32°F (-23 to 0°C)
Engine oil	SAE 10W single viscosity or SAE 10-30W multi-viscosity	API Service CC/CD/CE single; CC/CD/SF multi	-23°C to 0°C		-10 to 32°F (-23 to 0°C)
Engine oil	SAE 10W single viscosity; SAE 10-30W multi-viscosity	API Service CC/CD/CE or CC/CD/SF	-23°C to 0°C		-10 to 32°F (-23 to 0°C)
Engine oil	SAE 15-40W	API Service CC/CD/CE single viscosity or CC/CD/SF multi-viscosity	above 0°C	3.1 liters	Above 32°F (0°C) multi-viscosity
Engine oil	SAE 30W	API Service CC/CD/CE single viscosity or CC/CD/SF multi-viscosity	above 0°C	3.1 liters	Above 32°F (0°C); use SAE 30W during first 100 hours
Engine oil	SAE 30W (single viscosity) / SAE 15-40W (multi-viscosity)	API Service CC/CD/CE single viscosity oils; API Service CC/CD/SF multi-viscosity oils	above 0°C	3.1 liters	Above 32°F (0°C); engine capacity with new oil filter is 3.3 quarts (3.1 liters)
Engine oil	SAE 30W single viscosity or SAE 15-40W multi-viscosity	API Service CC/CD/CE single; CC/CD/SF multi	above 0°C	3.0 L	Above 32°F (0°C); capacity with new oil filter per SP2
Engine oil	SAE 30W single viscosity; SAE 15-40W multi-viscosity	API Service CC/CD/CE or CC/CD/SF	above 0°C	3.0 L	Above 32°F (0°C); capacity with new oil filter
Fuel	ASTM D975; grade no. 2 diesel above freezing 32°F (0°C); grade no. 1 below freezing and for all temperatures above 5,500 ft. (1500 meters)	ASTM D975			Sulfur less than 1% (preferably less than 0.5%); cetane number minimum 45; do not use domestic heating oils, Class B engine, Class D domestic fuels, Class E/F/G/H industrial or marine fuels, ASTM-D975-60T No. 4-D and higher
Fuel	Grade No. 1 diesel	ASTM D975	below 0°C		Below freezing 32°F (0°C) and all temperatures above 5,500 ft (1500 m)
Fuel	Grade No. 2 diesel above freezing 32°F (0°C); Grade No. 1 below freezing and at altitudes above 5,500 ft. (1500 meters)	ASTM D975; sulphur less than 1% (preferably less than 0.5%); cetane number minimum 45			Do not use domestic heating oils, Class B engine, Class D domestic fuels, Class E/F/G/H industrial or marine fuels, ASTM-D975-60T No. 4-D and higher
Fuel	No. 1 diesel	ASTM D975	below 0°C		Below freezing and for all temperatures at altitude above 5,500 ft (1500 meters); sulfur less than 1% (preferably less than 0.5%); cetane number minimum 45
Fuel	No. 2 diesel above freezing 32°F (0°C); No. 1 below freezing and above 5,500 ft	ASTM D975			Sulfur less than 1% (preferably less than 0.5%); cetane minimum 45
Fuel	Grade No. 2 diesel	ASTM D975	above 0°C		Above freezing 32°F (0°C); sulfur <1% (preferably <0.5%); cetane minimum 45
Fuel	No. 2 diesel	ASTM D975	above 0°C		Above freezing 32°F (0°C); sulfur less than 1% (preferably less than 0.5%); cetane number minimum 45

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Fault codes

Code	Name	Meaning	Action
04	Actuator drive wire disconnected	Detected when Engine ECU Power ON or Cranking.	Lamp action only when ECU power on; engine does not start during cranking
13	Oil pressure SW failure or wire disconnected	Lamp code 13: Long, Short, Short, Short. Detected when Engine ECU Power ON (EG Start Enable).	Go to Low Power Mode
15	Speed Sensor Failure or wire disconnected	Detected during Cranking or Engine Running.	Engine does not start during cranking; Go to Low Power Mode when running
22	Pressure Sensor failure or wire disconnected	Detected when Engine ECU Power ON (EG Start Enable) or Engine running.	Go to Low Power Mode
33	Pressure Sensor failure or wire disconnected	Detected when Engine ECU Power ON (EG Start Enable) or Engine running.	Go to Low Power Mode

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Procedures

Adjusting valve clearances adjustment

Tools: Feeler gauge, Wrench

Engine must be cold and NOT running.
Bring No. 1 cylinder to top dead center on compression stroke by aligning timing marks.
Remove rocker arm cover.
Loosen lock nut and adjust intake and exhaust valve clearance to 0.008 in. (0.2 mm).
Repeat for each cylinder.
Replace rocker arm cover and tighten nuts to 5 - 8 ft/lbs.

V-Belt Adjustment adjustment

Tools: thumb

Check tension and wear daily.
Press thumb at midpoint between fan pulley and alternator pulley.
Correct tension: belt depresses about 3/16 in. (5 mm).
Loosen alternator tensioning arm bolt and mounting bolt.
Pivot alternator toward engine left or right as required.
Tighten mounting bolt and adjusting bolt.
Recheck tension after tightening.
Recheck after running five minutes at low idle.

V-Belts (SP5) adjustment

Press on the belt at the midpoint between fan pulley and alternator pulley with your thumb.
Tension is correct if the belt can be depressed about 3/16 in. (5 mm).
Loosen the alternator tensioning arm bolt and the alternator mounting bolt.
Pivot the alternator at the mounting bolt toward the engine left or right side as required.
Tighten the mounting bolt and the adjusting bolt.
Recheck belt tension after tightening and again after running 5 minutes at low idle.

Valve Clearance Adjustment adjustment

Adjust after cylinder head bolts are retightened; engine cold and not running.
Turn engine by hand until #1 cylinder inlet valve starts to open and exhaust starts to close.
Turn crankshaft one more full turn and adjust both valves for this cylinder.
Loosen lock nut and adjust clearance between rocker arm and valve guide.
Set clearance to 0.008 in. (0.2 mm) for both intake and exhaust.
Repeat for each cylinder individually.
Replace rocker arm cover and tighten cover nuts to 7.2 - 8.7 ft/lbs.

Valve Clearances adjustment

Adjust valve clearance every 1000 hours, or as needed; engine must be cold and not running.
Turn engine by hand until inlet valve starts to open and exhaust valve starts to close (valves are rocking).
Turn crankshaft one more full turn and adjust clearance on both valves for this cylinder.
Loosen lock nut and adjust clearance between rocker arm and valve guide with adjustment screw.
Set both intake and exhaust valves to 0.008 in. (0.2 mm).
Repeat for each cylinder; adjust each set individually.
Replace rocker arm cover and tighten cover nuts to 5 - 8 ft/lbs (0.8 - 2.3 kg/m).

Valve Clearances (SP6) adjustment

⚠ Valve adjustments should be done after the cylinder head bolts have been re-tightened.

Adjust valve clearance every 1000 hours, or as needed; engine cold and NOT running.
Turn the engine over by hand until the inlet valve starts to open and exhaust starts to close (valves rocking).
Turn the crankshaft one more full turn and adjust the clearance on both valves for this cylinder.
Loosen the lock nut and adjust clearance with the adjustment screw.
Clearance on both intake and exhaust valves is 0.008 in. (0.2 mm).
Repeat for each cylinder; each set of valves must be adjusted individually.
Replace the rocker arm cover; tighten cover nuts to 5 - 8 ft/lbs (0.8 - 2.3 kg/m).

Valve clearance adjustment (SP6) adjustment

Tools: feeler gauge, wrenches

Retighten cylinder head bolts first; engine must be cold and NOT running.
Turn engine by hand until #1 cylinder inlet valve starts to open and exhaust valve starts to close.
Turn the crankshaft one more full turn and adjust both valves for this cylinder.
Loosen the lock nut and adjust clearance between rocker arm and valve guide with the adjustment screw.
Set clearance to 0.008 in. (0.2 mm) on both intake and exhaust valves.
Repeat for each cylinder; each set of valves must be adjusted individually.
Replace rocker arm cover and tighten cover nuts to 7.2 - 8.7 ft/lbs (1.0 - 1.2 kg/m).

Checking glow plugs diagnostic

Tools: D.C. test bulb

Loosen current-carrying flat wire between plus-poles of glow plugs.
Connect a D.C. test bulb between plus-pole of battery and plus-pole of glow plug.
If bulb lights, glow plug is functioning properly.
Check all glow plugs and replace faulty ones.

Flashing the fields diagnostic

⚠ The AVR must be disconnected when flashing fields or it could be ruined.

Tools: 12 volt DC source, voltmeter

If there is no voltage buildup on startup (zero volts measured), the generator may have no residual magnetic field.
Disconnect the AVR before flashing fields or it could be ruined.
Apply 12 volts DC to terminals K (-) and J (+) as indicated.
Reconnect AVR and check voltage buildup.

Soundshield Assembly and Installation installation

⚠ Generator sets with wet exhaust installed near or below the vessel's water line must use a siphon break to prevent backflow of water into the engine, which can ruin the engine and possibly sink the vessel

Inspect all components for damage and check the packing list before assembly
Loosen and rotate down original factory lifting points below the highest point on the engine, then retighten
Select mounting location per IM1000 Installation Manual on a rigid, flat surface above a strong structure
Position the enclosure so its left side and rear are 6 in recommended (4 in minimum) from bulkheads, avoiding corners with blocked overhead
Install toe brackets to each corner of the genset base flanges with machine screws, flat washers, and nylock hex nuts
Install the four vertical extrusions with bolting assemblies; leave loose enough for adjustment during building
Loosely install front and left-hand side panel retainer blocks to the vertical extrusions
Position the pre-assembled top frame with triangular penetration plate toward the front and tighten all bolting assemblies progressively
Install the junction box support cover into the cavity of the support bracket until firmly engaged
Install the rear sound shield panel, engaging top retaining clips and securing the bottom with bolts, flat washers, and shoulder washers
Bend the intake air snorkel hose into the rear panel notch without kinking or restricting airflow
Connect exhaust, sea water, fuel, DC control harness, battery, and AC output leads through the rear panel holes
If installing a siphon break, replace hole plugs with rubber grommets and route hoses per the IM1000 Installation Manual
Start the generator set and run under load to check for leaks of fuel, water, or exhaust gas
Install left side, front, top, and right side panels, and insert foam blocks into the base pan mounting foot pockets

Battery Care maintenance

⚠ Battery gas can explode; keep flames and sparks away from batteries.

Tools: hydrometer

Check electrolyte level daily; add distilled water to manufacturer's recommended level.
Check and clean batteries, cables, and cable terminals every 100 hours.
Clean corrosion with water and baking soda solution; flush with clean water.
Tighten terminals and grease them to inhibit corrosion.
Check battery condition with a hydrometer every 250 hours.

Bleeding fuel system maintenance

⚠ Fuel under pressure can penetrate skin

Tools: cardboard or wood for leak check

Loosen bleed screw A on top of filter.
Pump hand primer B until pure fuel without bubbles escapes.
Tighten bleed screw A.
Loosen bleed screw C; pump until pure fuel escapes.
If engine does not start, loosen one injector fuel line.
Crank until fuel escapes; tighten line; repeat each line.
After start, check for fuel leaks.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Voltage reconnection

Voltage	Phase	Connection	Leads	Notes
120		Connect U1 to U2 and V1 to V2 on the output terminal board	120 volt output leads to terminals U1 and V2	Select 120 volt output by connecting control terminal board to 120
120		Connect U1 to U2 and V1 to V2 on the output terminal board; connect 120 volt output leads to U1 and V2.	U1, U2, V1, V2	Control terminal board set to 120.
120		Connect U1 to U2 and V1 to V2 on the output terminal board; connect 120 volt output leads to terminals U1 and V2.	U1, U2, V1, V2	Control terminal board set to 120. See Figure 20 and Figure 21.
120		Connect control terminal board to 120; connect U1 to U2 and V1 to V2 on output terminal board	U1, U2, V1, V2	Connect 120 volt output leads to U1 and V2
120		Connect the terminals of the control terminal board to 120; connect U1 to U2 and V1 to V2 on the output terminal board; connect 120 volt output leads to terminals U1 and V2	U1, U2, V1, V2	Figure 20 and Figure 21, 120 Volt Output
120	1	Connect V1 and 120 terminals of the control terminal board; connect U1 to U2 and V1 to V2 on the output terminal board; connect 120 volt output leads to terminals U1 and V2	U1, U2, V1, V2	120 Volt Output
120	1	Control terminal board set to 120; output terminal board U1 to U2 and V1 to V2; output leads to U1 and V2	U1, U2, V1, V2	120 volt output
120/240		Connect U2 and V1 on the output board	Output leads to U1 and V2; neutral lead to V1 (or U2)	240 volt output available from leads connected to U1 and V2; divide 120 volt load equally between two 120 volt circuits
120/240		Connect U2 and V1 on the output board; connect output leads to U1 and V2 and neutral lead to V1 (or U2).	U1, U2, V1, V2	240 volt output available from leads connected to U1 and V2. Divide 120 volt load as equally as possible between two 120 volt circuits. See Figure 24 and Figure 25.
120/240		Connect control terminal board for 240; connect U2 and V1 on output board	U1, U2, V1, V2	Output leads to U1 and V2; neutral to V1 or U2; divide 120 V load equally between two circuits
120/240		Connect the control terminal board for 240 volts; connect U2 and V1 on the output board; connect output leads to U1 and V2 and neutral lead to V1 (or U2)	U1, U2, V1, V2	240 volt output available from leads connected to U1 and V2; divide the 120 volt load as equally as possible between two 120 volt circuits
120/240	1	Connect the control terminal board for 240 volts; connect U2 and V1 on the output board; connect output leads to U2 and V2 and neutral lead to V1 (or U2)	U1, U2, V1, V2	240 volt output available from leads connected to U1 and V2; 120 volt load should be divided as equally as possible between two 120 volt circuits
120/240	1	Control terminal board set to 240; output terminal board U2 to V1; output leads to U2 and V2; neutral to V1 (or U2); 240 volt output from U1 and V2	U1, U2, V1, V2	Divide 120 volt load as equally as possible between two 120 volt circuits
240		Connect U2 to V1 on the output terminal board		Select 240 volt output by connecting control terminal board to 240
240		Connect U2 to V1 on the output terminal board.	U2, V1	Control terminal board set to 240. See Figure 22 and Figure 23.
240		Connect control terminal board to 240; connect U2 to V1 on output terminal board	U2, V1	240 volt output selected
240		Connect the terminals of the control terminal board to 240; connect U2 to V1 on the output terminal board	U1, U2, V1, V2	Figure 22 and Figure 23, 240 Volt Output
240	1	Connect V2 to 240 on the control terminal board; connect U2 to V1 on the output terminal board	U1, U2, V1, V2	240 Volt Output
240	1	Control terminal board set to 240; output terminal board U2 to V1	U1, U2, V1, V2	240 volt output

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Parts cataloged across the Northern Lights 673 family

Part #	Description	Category
24-28003	Air Filter Element	Air filter
24-28300	Air Filter	Air filter
22-68000	Kit: new DST-61 regulator with fuse, fuse holder parts and two crimp lugs; includes mounting plate adaptor parts	Avr
22-68035	Kit similar to 22-68000 but does not include the fuse parts	Avr
DST-61	New DST-61 voltage regulator	Avr
M673L2	Platform vibration mounts.	Base
22-68304	Brush assembly	Brush
24-52020	Fuel Filter	Fuel filter
360720020	Fuel Filter Element	Fuel filter
052100280	Gasket (Marine application only, formerly #054109013)	Gasket
165996490	Gasket	Gasket
18-72004	Oil Drain Hose	Hose
18-78009	Hose Assembly 3/8" x 15" (used with oil pan 36-78006)	Hose
140406570	Suction Filter	Oil filter
24-02001	Oil Filter	Oil filter
24-08001	Oil Filter	Oil filter
040109059	Bearing	Service part / kit
040126210	Bearing	Service part / kit
110136445	Intake Valve Seat	Service part / kit
115017630	Piston, standard (includes key #16)	Service part / kit
115104050	Ring Kit, standard	Service part / kit
120026810	Camshaft Assembly (includes keys #2 - 6)	Service part / kit
120166370	Intake Valve	Service part / kit
120456320	Push Rod	Service part / kit
198517103	Bearing, Standard Upper	Service part / kit
198517107	Bearing, undersize 0.25 mm (formerly #198517106)	Service part / kit
198517112	Bearing, Standard Lower	Service part / kit
198517116	Bearing, undersize 0.25 mm (formerly #198517115)	Service part / kit
198517119	Bearing, undersize 0.50 mm (formerly #198517118)	Service part / kit
198517312	Bearing, standard (formerly #198517311)	Service part / kit
198517316	Bearing, undersize 0.25 mm (formerly #198517315)	Service part / kit
198517319	Bearing, undersize 0.50 mm (formerly #198517318)	Service part / kit
198517332	Bearing, Standard Upper (formerly #198517331)	Service part / kit
198517336	Bearing, undersize 0.25 mm (formerly #198517335)	Service part / kit
198517339	Bearing, undersize 0.50 mm (formerly #198517338)	Service part / kit
198517342	Bearing, Standard Lower (formerly #198517341)	Service part / kit
198517346	Bearing, undersize 0.25 mm (formerly #198517345)	Service part / kit
198517349	Bearing, undersize 0.50 mm (formerly #198517348)	Service part / kit
198517630	Bearing, undersize 0.50 mm (formerly #198517109)	Service part / kit
22-48011	Fuse for main circuit (M/NL 673)	Service part / kit
22-68305	Generator bearing	Service part / kit
22-68309	Protective Fuse (for AVR)	Service part / kit
28-68003	Adaptor mounting plate	Service part / kit
38-08015	Northern Lights standard spare parts kit	Service part / kit
38-08019	Northern Lights world class spare parts kit	Service part / kit
052109078	O-ring, Relief Valve	Seal
052109113	O-ring	Seal

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.

Common questions

What is the oil capacity of the Northern Lights L673L?

The Northern Lights L673L engine has an oil capacity of 3.1 liters.

What is the displacement of the Northern Lights L673L?

The Northern Lights L673L has a displacement of 0.76 liters with 3 cylinders.

Which generators use the Northern Lights L673L engine?

The Northern Lights L673L powers 2 generator set(s), including Northern Lights M673, Northern Lights NL673.

How often should you change the oil in the Northern Lights L673L?

The Northern Lights L673L oil change interval is every 250 hours.

What is a common problem with the Northern Lights L673L engine?

A commonly reported issue on generators using the Northern Lights L673L is: Engine Hard to Start or Will Not Start. Cause: Improper starting procedure. Fix: See starting section of this manual. Take special note of Bypass Switch operation.