Top 10 Most Common Portable Generator Repair Questions Answered

Why won’t my portable generator start?

When a portable generator won’t start, the issue is usually simple: fuel, spark, or air. Begin with the basics:

1. Check fuel level and age. Old gasoline (over 30–60 days) can cause hard starting. Drain and refill with fresh, stabilized fuel.
2. Inspect the ON/OFF and fuel valves. Make sure the engine switch is ON and the fuel shutoff valve is open.
3. Check the choke position. Use FULL CHOKE for a cold start, then gradually move to RUN once it fires.
4. Examine the spark plug. Remove it, clean or replace if fouled, and ensure the wire is firmly connected.
5. Confirm the oil level. Many generators won’t start if oil is low.

Call a professional if there’s fuel and spark but it still won’t start, or you smell strong fuel with no ignition (possible carburetor or ignition coil issue).

Why does my generator start but then shut off after a few seconds?

This symptom often points to fuel delivery, low oil, or overload protection. Common causes:

• Low oil level triggering the low-oil shutdown sensor 🛢️
• Clogged carburetor jets or dirty fuel
• Blocked fuel vent in the gas cap (creates a vacuum in the tank)
• Overloaded with too many devices plugged in

Quick checks:

1. Verify oil is at the correct level.
2. Loosen the fuel cap slightly while it runs—if it stays on, the cap vent may be clogged.
3. Temporarily unplug all loads and restart. If it runs fine with no load, you were likely overloading it.
4. Add fuel treatment or clean the carburetor if it sat with old gas.

Call a technician if it repeatedly stalls even with proper oil, fresh fuel, and no load.

Why is my generator running but not producing power?

If the engine runs but there’s no electricity, the problem is in the alternator or outlets, not the engine.

1. Check the breaker(s). Many generators have resettable circuit breakers—make sure they’re not tripped.
2. Confirm the main power switch or output switch is ON (some models have separate AC ON/OFF switches).
3. Test multiple outlets with a known-good device or outlet tester.
4. If it sat unused for months, the generator may have lost residual magnetism in the alternator.

DIY attempt: Some users restore magnetism by briefly “flashing” the field with DC power, but this can be dangerous and model-specific. ⚠️

Call a professional if breakers are fine and no outlets have power, or if you suspect alternator, AVR (automatic voltage regulator), or wiring failure.

Why does my portable generator keep tripping the breaker?

Frequent breaker trips usually signal overload or a short circuit in the generator or connected devices.

Troubleshooting steps:

1. Unplug everything, reset the breaker, and start the generator.
2. Plug in one device at a time, starting with the smallest load.
3. Check your generator’s rated watts vs. starting watts and compare to your appliances’ labels. Devices with motors (AC units, fridges, pumps) can draw 2–3× their running wattage at startup.
4. Inspect cords and plugs for damage, melting, or burn marks.

If breakers trip with no load, or there’s visible arcing, burning smell, or melted plastic, stop using the generator and call a pro immediately. 🔧

Why is my generator surging or revving up and down?

Surging (engine speed going up and down) points to fuel, governor, or load issues.

Most common causes:

• Dirty carburetor or restricted fuel flow
• Clogged air filter choking airflow
• Unstable or very small load on standard (non-inverter) generators
• Maladjusted governor or throttle linkage

What to do:

1. Run the unit with a moderate, steady load (like a 500–1000W space heater). If surging improves, it may be normal governor behavior at low load.
2. Clean or replace the air filter.
3. Add carburetor cleaner or fuel system cleaner to fresh fuel; run for 20–30 minutes.
4. Check for kinks in the fuel line.

If surging continues under medium load with clean fuel and air filter, or the engine backfires or emits black smoke, get professional service—governor or carb adjustment may be needed.

Why does my generator smell like gas or leak fuel?

Fuel smells or visible leaks are serious 🔥. Shut the generator off, let it cool, and address the problem before using it again.

Common leak sources:

• Cracked fuel lines or primer bulb
• Loose hose clamps
• Leaking carburetor bowl gasket
• Overfilled tank or venting near the cap

Steps to take:

1. Move the unit outdoors, away from any flames or sparks.
2. Inspect under and around the carburetor, fuel lines, and tank.
3. Tighten any obvious clamps; replace brittle or cracked fuel hoses.
4. Do not use open flames to look for leaks—use a flashlight.

If fuel drips heavily, you see puddles, or smell is overwhelming, stop using the generator and call a technician. Do not store it indoors until repaired.

Why is my generator so loud, and can that mean something’s wrong?

Portable generators are naturally loud, but sudden increases in noise can indicate a problem.

Normal vs. concerning noises:

• Normal: Steady engine hum, exhaust noise, slight increase under heavy load
• Concerning: Metallic knocking, rattling, hissing, or sharp pops/backfires

Things to check:

1. Inspect muffler and spark arrestor—loose or damaged parts can increase noise and fire risk.
2. Make sure all panels and bolts are tight; vibration can loosen hardware.
3. Listen for knocking that gets louder under load—may indicate internal engine wear or running low on oil.
4. Confirm you’re using the correct fuel and oil grade.

If you hear loud knocking, grinding, or the generator suddenly becomes much noisier, shut it down and have it inspected. Internal damage can be costly if ignored.

Why does my generator keep shutting off when I plug in my RV or home transfer switch?

If your generator dies when powering an RV or home circuit, it may be due to overload, improper connection, or backfeeding issues.

Key checks:

1. Confirm your generator’s rated and surge wattage can handle the combined loads (AC, microwave, fridge, etc.).
2. Turn off major RV or household breakers, start the generator, then turn on circuits one at a time.
3. Ensure you’re using the correct RV or transfer switch inlet (30A vs 50A) and proper cables.
4. Verify the choke is in RUN and engine is fully warmed up before applying heavy loads.

If you suspect wiring or transfer switch issues, do not attempt DIY fixes inside your panel—hire a licensed electrician.

Why is my generator hard to start in cold weather?

Cold temperatures make engines harder to crank and fuel harder to vaporize ❄️.

Common cold-start issues:

• Thick oil causing drag on the engine
• Choke not used correctly
• Old fuel less volatile
• Weak battery on electric-start models

How to improve cold starts:

1. Use the manufacturer-recommended winter oil (often 5W-30 instead of 10W-30).
2. Store the generator in a sheltered but ventilated area (never living space) to keep it slightly warmer.
3. Always use FULL CHOKE when first starting, then move gradually to RUN.
4. Keep the battery charged with a maintainer on electric-start units.
5. Use fresh, winter-grade fuel with stabilizer.

If the pull cord is almost impossible to pull, or the engine backfires heavily, wait for warmer conditions or get a technician to check compression and ignition timing.

How often should I change the oil, and what happens if I don’t?

Oil is critical for the small, high-RPM engines in portable generators. Neglected oil leads to overheating, premature wear, and engine failure.

General guidelines (always check your manual):

• First oil change: After the first 5–10 hours (break-in)
• Ongoing: Every 50–100 hours of use or at least once per year
• Change more often in dusty, hot, or heavy-load conditions

If you skip oil changes, contaminants build up, viscosity breaks down, and the engine can seize, often making repair more expensive than replacement. If the oil is very dark, thick, or smells burnt, change it before the next use. If the engine shuts off and won’t restart, and oil is very low, call a professional—internal damage is likely.

Helpful Tips for Keeping Your Portable Generator Running Smoothly

1. Run it monthly for 10–20 minutes with a small load to keep fuel fresh in the carburetor and maintain alternator magnetism.
2. Use fresh, stabilized fuel and rotate stored fuel every 2–3 months; avoid ethanol-heavy gas if your manual warns against it.
3. Change oil, air filter, and spark plug on a schedule, and log maintenance dates on a tag attached to the handle.
4. Store the generator dry and covered, but never with a sealed plastic wrap—allow ventilation to avoid condensation and corrosion.
5. Drain or run the carburetor dry before long-term storage to prevent varnish buildup.
6. Inspect cables, plugs, and grounding before each use to reduce shock and fire risks and prevent damage to your appliances.