Northern Lights L673L Engine Engine
The Northern Lights L673L is a 0.76 L 3-cylinder naturally aspirated engine rated at 1800 rpm. It powers generator sets from Northern Lights, including the M673, M673LD3 and NL673L4.
Also known as: Northern Lights L673L
Engine specifications
| Displacement | 0.761 L |
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| Cylinders | 3 |
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| Aspiration | naturally aspirated |
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| Rated speed | 1800 rpm |
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Generator sets powered by this engine
3Common problems
15- Temperature gauge shows temperature within normal range but shutdown is activated
Fix: Check the engine crankcase oil level. If 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. If the oil level is normal, DO NOT restart the engine. Call your dealer for assistance. - Starter Inoperative
Cause: Check DC circuit breaker, Loose or corroded connections
Fix: If the breaker is tripped, reset it, Clean and tighten loose battery and harness plug connection - Starter Cranks Slowly
Cause: Low battery output, Crankcase oil too heavy
Fix: Battery is too small, Battery cables are too small, Check specific gravity of each battery, Check electrolyte level of each battery, Fill with oil of appropriate viscosity, Clean and tighten all battery connections - No fuel
Fix: Check level of fuel in fuel tank - Low Oil Pressure
Cause: Low coolant level, Defective thermostat, Temperature gauge not working properly
Fix: Fill crankcase to proper level, Fill tank or radiator to proper level, Check thermostats, Check water temperature with thermometer and replace gauge if necessary - Lack of Engine Power
Cause: Intake air restriction, Clogged primary fuel filter element, Clogged secondary fuel filter element
Fix: Service air cleaner, Clean or replace filter element, Replace filter element - High Oil Consumption
Cause: Defective thermostat, Defective temperature gauge
Fix: Remove and check thermostat, Check water temperature with thermometer and replace gauge if necessary - High Fuel Consumption
Cause: Injection pump out of time
Fix: See your dealer - Entire Electrical System Does Not Function
Cause: Check DC circuit breaker, Faulty connection, Sulfated or worn out batteries, Improper starting procedure
Fix: If breaker is tripped, reset it, Clean and tighten battery and harness plug connections, Check specific gravity and electrolyte level of each battery, See starting section of this manual, Take special note of Bypass Switch operation - Engine Temperature Below Normal
Cause: Thermostats not working properly
Fix: Check thermostats - Engine Runs Irregularly or Stalls Frequently
Cause: Below normal engine temperature, Clogged primary fuel filter element, Clogged secondary fuel filter element, Water or dirt in the fuel system, Dirty or faulty injection nozzles, Air in fuel system, Improper type of fuel, Overheated engine
Fix: Remove and check thermostat, Clean or replace filter element, Replace secondary filter element, Drain, flush, fill and bleed system, Have your dealer check injection nozzles, Inspect clamps and hoses on suction side of fuel pump for air leak, Consult fuel supplier and use proper type of fuel for operating condition, See “Engine Overheats” in next category - Engine Overheats
Cause: Improper valve clearance, Dirty or faulty injection nozzles, Air in fuel system, Improper type of fuel, Water or dirt in the fuel system, Clogged primary fuel filter element, Clogged secondary fuel filter element
Fix: Reset valves, Best done by dealer, Replace injectors, Best done by dealer, See your local dealer, Service air cleaner, Clean or replace filter element, Replace secondary filter element - Engine out of time
Fix: See your dealer - Engine Knocks
Cause: Defective muffler (back pressure too high), Insufficient oil, Defective temperature gauge
Fix: Have dealer check back pressure, Call your dealer, Check water temperature with thermometer and replace gauge if necessary - Engine has shutdown
Fix: Check the temperature gauge. If above 205°F (96°C) for marine units or 230°F (110°C) for industrial units, shut off the engine immediately. Use the Trouble Shooting Guide on page 24 to isolate the cause of the overheat.
Compiled from service & troubleshooting documentation across every generator set that uses the Northern Lights L673L.
Maintenance schedule
| Item | Spec | Capacity | Part # | Interval | |
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| Fuel filter | large spin-on fuel filter | | — | | find |
| Oil filter | spin-on oil filter with bypass | | — | | find |
| Belt | | | — | | find |
| Oil | spin-on oil filter with bypass | 3.1 qt (ltr) | — | 200 hr | |
Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.
Common questions
What is the displacement of the Northern Lights L673L?
The Northern Lights L673L has a displacement of 0.761 liters with 3 cylinders.
Which generators use the Northern Lights L673L engine?
The Northern Lights L673L powers 3 generator set(s), including Northern Lights M673, Northern Lights M673LD3, Northern Lights NL673L4.
How often should you change the oil in the Northern Lights L673L?
The Northern Lights L673L oil change interval is every 200 hours.
What is a common problem with the Northern Lights L673L engine?
A commonly reported issue on generators using the Northern Lights L673L is: Temperature gauge shows temperature within normal range but shutdown is activated. Fix: Check the engine crankcase oil level. If 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. If the oil level is normal, DO NOT restart the engine. Call your dealer for assistance..