What to Do When Your Backup Generator Won’t Start

Power outages are stressful enough. When your backup generator won’t start, suddenly you’ve lost the safety net you were counting on for lights, heat, and food protection. The good news is that many “no start” problems come from a few common culprits like fuel supply, battery health, or an automatic safety shutdown.

This guide covers safe checks you can do from the outside using your owner’s manual and basic visual inspection. Let’s start by going over the most common reasons a generator fails, since that quickly narrows down what to check first.

The Most Common Causes of Backup Generator Failure

A generator not working usually has one of these issues:

• The battery is weak, dead, corroded, or loosely connected
• Oil level is low, triggering a protective shutdown
• Fuel is empty, shut off, stale, or not flowing correctly
• The generator breaker is tripped, the fuse is blown, or the controller shows a fault code
• The air filter is clogged, or the spark plug is worn or fouled
• The standby system has a transfer switch or control problem

Note: Generator safety matters during troubleshooting. Portable generators should run outdoors only, well away from doors, windows, and vents.

What to Check When Your Generator Won’t Start

Start with safety, then work through a simple checklist. Skip opening electrical panels or the generator’s internal wiring compartment. Those areas can hold dangerous voltage and create shock or fire risk.

Safety Steps Before You Check

• Turn the generator OFF and let it cool
• Run portable units outdoors only, on a flat surface
• Keep it at least 20 feet from the home and point the exhaust away
• Follow your manual for fault codes and reset steps
• Stop if you smell fuel or see a leak

Note: Never backfeed power into a home through a wall outlet or panel. Use a properly installed transfer switch or interlock.

Generator Inspection Checklist

1. Confirm the emergency stop is released, and the unit is in the correct mode
2. Check the controller for a fault code or warning light
3. Confirm the generator breaker is ON
4. Verify fuel level and open fuel valves
5. Check the oil level and look for low oil indicators
6. Listen during start: Clicking or slow cranking often points to a battery issue, while no sound can point to a switch setting, breaker, or control problem

Fuel System Inspection

Fuel issues are a top reason a generator may not start after months of sitting.

• For portable generators: confirm you have fresh fuel, the fuel valve is open, and the choke is set correctly for startup. If the fuel smells sour or looks dark, it may be stale. Follow your manual for safe draining and refilling.
• For standby generators: confirm the natural gas shutoff is open, or the propane tank level is adequate. If there is a strong gas smell, stop and contact a professional right away.

Oil & Battery Checks

Oil and battery problems are two of the biggest reasons a generator won’t start, and they are also two of the easiest things to check without taking anything apart.

Note: Work slowly, follow your manual, and keep everything clean and dry.

• Oil: Many generators won’t start when oil is low because the system is protecting the engine. Check the dipstick and top off only with the oil type listed in your manual.
• Battery: If starting is slow, the battery may be weak. Check for corrosion on the terminals and make sure connections are snug. If the battery is aging, replacement is often the most reliable fix.

Air Filter, Spark Plug, & Controls

If the fuel and battery seem fine, the next step is making sure the engine can breathe, ignite, and read the right settings. These checks are quick, and they catch a lot of “it ran last season” problems.

• Air filter: A clogged filter limits airflow and can prevent starting. Replace it if it looks dirty.
• Spark plug: On portable generators, a worn plug can cause no start or rough running. Use the exact plug type listed in your manual.
• Controls: Confirm the unit is set correctly. Standby systems typically need AUTO for normal operation. Portables often need RUN plus the correct fuel valve and choke settings.
• Fault codes: Write down the code and message before you reset anything. That detail helps if troubleshooting moves beyond DIY.

DIY Fixes For When Your Generator Isn’t Working 

If the checklist points to a simple issue, these fixes are usually safe:

• Recharge or replace the battery
• Clean light corrosion from terminals
• Replace the air filter
• Replace the spark plug if your manual allows it
• Reset the controller using the manufacturer’s steps
• Clear leaves and debris around the unit for ventilation

After it starts, let it run for a few minutes before adding load. Then, add power gradually to avoid bogging the engine down.

When to Call a Professional for Generator Repair or Replacement

Some problems need trained diagnostics, electrical testing, or fuel system work. 

A professional generator repair service is the right move when any of these show up:

• The generator starts, then shuts off quickly
• Fault codes keep returning after a reset
• Power does not transfer correctly during an outage
• Strong fuel odor or suspected leak
• Visible wiring damage, melted parts, or heavy corrosion
• You suspect a transfer switch issue on a standby system

Transfer switches keep utility power and generator power separated. That separation helps protect people, equipment, and line workers. Backfeeding and unsafe connections are a serious hazard.

If repairs are stacking up on an older unit, replacement can be the better long-term plan. A licensed electrician can help you size the system, confirm fuel supply, and make sure the connection method is code-compliant.

Keep Your Backup Power Ready for the Next Outage

Once you’ve worked through the checks above, you should have a clearer idea of what stopped your generator from starting. If it still won’t run, stop and avoid repeated attempts that can drain the battery or add wear. Instead, have the system tested properly for startup, load performance, and transfer operation. 

Backup power is more dependable when it gets regular attention: a yearly inspection and a quick test run. At Rhema Electric, we offer our Safety and Savings Membership for that very reason. It includes:

• Annual residential electrical inspection
• Priority scheduling for service calls
• 15% off standard installation and repair (some exclusions apply)
• A reduced dispatch fee
• Lifetime labor warranty on workmanship (for fixtures installed by Rhema)

Keep it maintained and tested, and your generator will be ready when your home needs it most!

Call Rhema Electric in Western Washington for Generator Troubleshooting, Repair & Replacement

Can’t get your generator running again? Reach out to Rhema Electric for the best electrical service in Western Washington. Our experienced electricians can pinpoint the issue, explain what failed in plain language, and recommend a solution that fits your home and your backup power goals. Get straightforward pricing and a clear plan, so you can stop guessing and get back to normal.