Northern Lights Marine Generator Troubleshooting Guide

Northern Lights Generator troubleshootingNorthern Lights marine generators generally do not have many issues, as long as proper maintenance and changing of filters is kept up with… however, if you are experiencing an issue with your generator, the problems are generally pretty easy to figure out / fix.

In order to help address these common issues, we’ve put together this Northern Lights Generator Troubleshooting Guide.

Below we’ve compiled the main issues that you may face with a Northern Lights generator, and provide you with solutions. Should you have any more questions, or concern about any of these issues, please contact Northern Lights support directly. This advice is meant to help, but not to replace advice from a specialist or Northern Lights support.

IMPORTANT: Make sure to review warnings and safety precautions* below before working on marine generator. If not familiar / comfortable with working on machinery such as a generator, consider contacting an expert.

Battery Not Charging?

  • Loose or corroded connections (clean and tighten connections to battery)
  • Sulfated / worn out batteries (check specific gravity of batteries using a hydrometer, check electrolyte levels)
  • Loose or dysfunctional alternator belt (tighten or replace belt)

Starter Not Working on Marine Generator?

  • Check DC circuit breaker (reset if necessary)
  • Loose or corroded connections (clean and tighten loose battery and harness plug connection)
  • Low battery output (check electrolyte and specific gravity levels)
  • Defective ground wire (replace wire)

Engine Difficult To Start or Won’t Start?

  • Check fuel levels
  • Low battery output (check electrolyte levels and connection, tighten all connections)
  • Crankcase oil too thick (use proper oil, proper viscosity)
  • Improper fuel (consult fuel supplier; verify proper fuel type)
  • Water, dirt or air in fuel system (drain, flush, fill, bleed system)
  • Clogged primary or secondary Northern lights fuel filter element (Clean or replace primary filter element, replace secondary filter element)
  • Dirty injection nozzles (check injectors, replace if necessary)
  • Fuel injection but no ignition (glow plug malfunction, incorrect injection timing, low compression pressure in cylinder)

Marine Generator Engine Overheating?

  • Low coolant, or defective cooling system (refill coolant, check hoses for leaks/loose connections, slipping fan belt)
  • Keel cooling tubes have been painted (remove paint if possible, otherwise replace keel cooling tube)
  • Defective thermostat (check, and replace thermostat if necessary)
  • Defective temperature gauge (check water temperature with thermometer, and replace gauge if necessary)
  • Water pump impeller worn / broken (check water pump impeller, and replace if necessary)

Low Oil Pressure?

  • Low oil level (fill crankcase to proper level)
  • Clogged filter and strainer or worn bearings and oil pump (repair or replace necessary part for your model)
  • Partially plugged oil filter? (replace Northern Lights oil filter)


*Warning and Safety Precautions Before Working On Marine Generator

  • Do not start engine by shorting across start terminal. Start only from operator’s station.
  • Diesel is highly flammable, don’t smoke or be near possible source of sparks / flames
  • Stop engine before fueling. Never fuel a hot engine.
  • Do not wear dangling clothing or jewelry while working on machine.
  • Disconnect battery ground cable before working on generator.
  • Contact with fans, belts, pulley and drives in operation will cause serious injury. Be aware
  • Battery gas is highly flammable
  • Frozen batteries may explode if charged
  • Battery electrolyte can burn through skin or closing, beware
  • Work in an open area
  • Relieve pressure before disconnecting pressurized lines. Escaping fluid under pressure can penetrate skin and cause serious injury. Make sure all connections are tight before re-applying pressure.


These are just some of the most common technical issues with marine generators. Should you have any further issues, please contact a specialist or Northern Lights support.

Have a good one!
1 (800) 766-5256

Extra resources:

  • Quick reference filter chart for Northern Lights oil, air and fuel filters, see here…

Related information:


    Jeff spafford November 5, 2017

    Hello my name is Jeff,
    My northern lights 9k generator which is only 4 years old recently started dropping in volts occasionally. The generator will drop in volts from 110 to around 69 volts for a few hours and then come back up. Any info would be greatly appreciated.

      Citimarine Store November 6, 2017

      Hi Jeff, sounds like it’s the voltage regulator board. If you provide us with the serial number of your unit, we can get you an estimate for the board.

    Tom November 14, 2017

    We have an M773LW3.3 that has 389 hours on it. It’s been properly maintained and serviced, but it suddenly stopped working in the middle of the night. It will fire up and run for a few seconds, but then it shuts off and the 10 amp breaker ON the generator trips. We cannot attempt to restart it until we turn the breaker (on the generator) off and on, then hit the reset button (also on the generator). There COULD be an issue with the fuel pump, or grounding… but it was running perfectly prior to it shutting down in the middle of the night.

      Citimarine Store November 14, 2017

      Hello Tom, That can be caused by a number of different issues. Would be best to have a specialist take a look at it, in order to better diagnose the problem. A good start would be contacting Northern Lights directly, in order to get a good referral near you: 1-800-762-0165

    Chris December 8, 2017

    Have a 9kw generator will not start after shaking and black smoke then cut out suspect fuel injector pump is faulty becaus Crack lines and fuel just trickling out when cranking. Is there any way to check injector pump

      Citimarine Store December 11, 2017

      In order to check if it is the injector pump, you would need to remove it and send it to a local fuel injection pump repair specialist. If you are getting a lot of shaking and black smoke, you may want to check for something else inside the engine as well.

    David Dunn December 30, 2017

    I have a 8k northern lights generator with over 2300 hrs on it , started blowing oil dip stick out and blowing oil out ,any ideas on what is going on ,generator shut down on low oil pressure ,

      Citimarine Store January 8, 2018

      Most likely you have a bad ring, and that’s the reason you’re getting pressure into the lower system. I will send you more information via email.

    Justin gross January 14, 2018


    I have a older M813-12N(saw series) generator which is producing low voltage. around 79v on both lines. Capacitors test ok. Any ideas where the issue may contribute from?
    Appreciate any assistance you can offer

      Citimarine Store February 9, 2018

      Hello Justin, more than likely there is a bad connection that is causing this I would start there first.

    Gary L Baldozier January 19, 2018

    I have a NL 673L2, recently the cycles per second has dropped from 60 to 57 CPS, the volts between 110 and up. Do I correct both thru the AVR?

      Citimarine Store February 9, 2018

      Hi Gary,

      1. Check all electrical connections

      2. Check the frequency gauge for accuracy

      3. Check fuel filters

      4. The AVR is not able to adjust the HZ

    Dave Calvert January 21, 2018

    We have a 9KW Northern Lights generator. When running, the line voltage needle will flutter back and forth for about 15 minutes at a time. The RPMs decrease when this is happening. What can cause this?

      Citimarine Store February 9, 2018

      Hi Dave,

      1. Check your fuel filter

      2. Check fuel valves

      3. Check for kinked fuel lines

      4. Check for anything that can cause a fuel restriction

    Chris January 24, 2018

    Hi can any body tell me what the cylinder head torque for the northanlights M773lW. 3 engin is also what is the compression on that engine.

    richard gardner February 1, 2018

    8 kw with 56 hrs getting diesel in oil changed oil still smells like diesel over the mark

      Citimarine Store February 9, 2018

      Likely to be a leaking injector, leaking lift pump or leaking injector pump

    Gary Hollenbeck April 7, 2018

    I have a norther lights PX312K1 The gerenerator start but after running for 5 minutes shuts off. It acts like the fuel cuts off or overheats. I have changed the filters and it does not overheat. Any suggestions. Thanks, Gary

      Citimarine Store April 13, 2018

      Did you change both, the primary and the secondary filter?

      If you did, please check your water exhaust temperature sender, you may have a faulty sender.


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