Before you buy a used diesel generator, ask for a load bank test, check the engine hours and service records, start it cold, and inspect for leaks, exhaust smoke and stable voltage and frequency under load. A generator that passes these checks will usually give many more years of service. This checklist is the one we follow at IronPower Industries before a unit goes up for sale.
1. Paperwork and history
- Hours. Read the hour meter and compare it with the year and the general condition. Rental-fleet units often have complete service records.
- Service records. Oil, fuel, air and coolant filter changes at regular intervals.
- Data plate. Confirm the kVA or kW rating, voltage options, phase and emissions tier match what you need.
2. Visual inspection
- Oil, fuel or coolant leaks under the engine and around hoses.
- Radiator condition, belts and coolant level.
- Enclosure, doors and sound insulation. Corrosion matters on units that worked near the coast.
- Wiring, breakers, receptacles and the control panel.
- On towable units: trailer frame, tires, lights, hitch and fuel tank.
3. Start and run
- Cold start. It should start promptly without excessive cranking.
- Exhaust. Light smoke at startup is normal. Continuous blue, black or white smoke points to engine problems.
- Sound and vibration. Listen for knocking and check that it runs smoothly.
- Gauges. Oil pressure, coolant temperature, voltage and frequency should be steady.
4. Load bank test
A load bank test makes the generator carry a real electrical load in steps up to its rated output. It proves the unit delivers its rated power, holds voltage and frequency, and does not overheat. It also burns off the carbon left by long periods of light use, a problem explained in wet stacking explained. Ask the seller for the test results, and be cautious with any unit sold without one.
5. Match the size to your load
A generator in great condition is still the wrong purchase if it is too small or far too large. Use our guide on what size diesel generator you need before you decide. As a price reference, used 25 kVA units in our inventory have been listed from $8,500 to $16,500 and 125 kVA units from $20,500 to $36,500.
Frequently asked questions
How many hours is a lot for a diesel generator?
Industrial diesel generators are built for long service lives, so maintenance history matters more than the number on the meter. A well-serviced unit with higher hours is often a better buy than a neglected one with low hours.
What is a load bank test?
It is a test that applies a controlled electrical load to confirm the generator produces its rated output and runs at a stable voltage, frequency and temperature.
Should I buy a towable or a skid-mounted generator?
Towable units are best when you move between jobsites. Skid-mounted units suit permanent or long-term installations.
Every unit in our used diesel generators for sale is inspected and load tested. Contact us for test results or a freight quote.
