Generator repair: what to know

What the job involves, what changes the price, and what to ask a pro.

What generator repair is

Generator repair gets a portable or standby generator running again when it will not start, loses power under load, or runs rough. The technician checks the fuel, ignition, battery, transfer switch and controls to find the failed part. Call when the generator fails during an outage, or when it starts but stalls, surges, or runs with a loud knock.

Signs you need it

  • The generator cranks but will not start, or it starts and then dies within moments
  • The generator loses power under load, or the voltage drops when appliances start
  • The engine runs rough, surges or hunts for speed
  • A standby unit fails its weekly self-test, or the transfer switch does not move to generator power during an outage
  • The generator smells of fuel or shows fuel leaks around the carburetor, pump or line
  • The battery is weak, the charger light is off, or the control panel shows a fault code

What the pro does

  • Check the fuel supply, the fuel filter and the fuel line for restrictions, leaks, or old or contaminated fuel
  • Test the spark plug or ignition module, and check the spark timing with the correct tool
  • Test the battery, the charger and the starter circuit, and clean the battery terminals
  • Test the transfer switch and its control wiring to confirm it moves to generator power under a utility loss
  • Check the voltage and frequency under load, and test the output breaker and receptacles
  • Replace the failed part, run the unit under load, and confirm it holds steady before the job is closed

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Whether the fault is a simple part, such as a spark plug or filter, or a deeper engine or control problem
  • Standby or portable type, and whether the transfer switch is part of the repair
  • Age of the generator and whether the parts are still available
  • Access to the unit, including whether it sits on a roof, behind a fence or in a tight enclosure
  • Whether the fuel system needs cleaning, draining or a line repair
  • Whether the control panel or a board needs replacement

What a written quote should spell out

  • The fault found and the test that confirmed it
  • Each part replaced, with its part number and match to the unit
  • Fuel system work performed, including any leak test
  • Transfer switch test results and the utility-loss test performed
  • A load test result that shows the unit holds voltage and frequency

Questions to ask before you hire

  • Will you check the fuel first, or go straight to the engine?
  • How will you confirm the transfer switch moves to generator power in an outage?
  • Can you test the unit under load, not just with the engine idling?
  • Are the parts you need in stock, or will the unit be down longer?
  • If the engine has major damage, will you tell me before you start a costly repair?
  • Will you show me the fault codes or the test readings before you close the job?

Red flags

  • Replaces the carburetor or pump without checking the fuel quality or the line
  • Says the unit is fixed after an idle run, with no load test
  • Ignores the transfer switch when the complaint is that power did not come on during an outage
  • Recommends a new generator without testing the failed part
  • Leaves fuel residue or a fuel smell in the enclosure after the repair

What you can do yourself

Checking the fuel level, changing the air filter, and keeping the unit clean and outdoors are safe. Opening the fuel system, adjusting the carburetor, and testing the transfer switch involve fuel, hot engine parts and live output, so they need a qualified technician. Never run a generator in an enclosed space or near a window, and never connect it to the house without a transfer switch.

Licenses and permits

Generator repair is commonly done by licensed technicians and, when it involves the transfer switch or the house wiring, by a licensed electrical contractor. Fuel line repair may need a separate license. Check with your state or local licensing agency for the rules that apply to the fuel and electrical parts of the repair.

Generator repair questions

Why does my generator start and then die?

Common causes are old fuel, a clogged fuel filter, a fouled spark plug, or a fault in the ignition or the carburetor. A technician tests the fuel first, then the spark and the air flow before replacing parts.

Why did my standby generator not take over during an outage?

The fault may be in the generator, the battery, the transfer switch or the control panel. A technician checks each of these with the unit under test, so the test confirms the full path.

Is stale fuel a problem if the generator sits for months?

Yes. Fuel breaks down over time and can gum the carburetor, the injectors or the fuel lines. Ask the technician how to store or treat fuel in your unit.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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