How to Start a Diesel Generator That Has Been Sitting for a Long Time

Diesel generators are reliable workhorses when maintained and used regularly. 

However, when a diesel generator has been sitting idle for an extended period, starting it can be challenging. 

Whether it’s been months or even years since your generator was last used, this guide will help you get it up and running safely. 

By following these steps, you can avoid damaging the unit and ensure optimal performance.

Why Diesel Generators Become Hard to Start After Sitting Idle

Diesel generators can develop issues when left unused for a long time due to:

1. Fuel Degradation: Diesel fuel deteriorates over time, forming sludge and contaminants.

2. Battery Drainage: Generator batteries may lose charge or fail entirely.

3. Lubrication Problems: Oil may degrade, lose viscosity, or settle in the engine.

4. Rust and Corrosion: Internal components can rust or corrode when not in use.

5. Clogged Filters: Dust and dirt in the air or fuel filters can lead to blockages.

Understanding these potential problems will help you address them during the starting process.

Step-by-Step Guide to Start a Diesel Generator That Has Been Sitting for a Long Time

1. Conduct a Visual Inspection

Before attempting to start the generator:

• Check for visible damage: Inspect wires, hoses, and belts for wear, cracks, or rodent damage.

• Inspect fuel levels: Ensure the fuel tank is adequately filled with clean diesel.

Pro Tip: Replace old fuel if it has been sitting for more than six months.

2. Test the Battery

• Check the battery voltage using a multimeter.

• Recharge or replace the battery if necessary.

• Clean the terminals to ensure proper electrical contact.

3. Inspect and Change the Oil

• Check the oil level and its condition. If the oil appears dark or has debris, replace it.

• Use the manufacturer-recommended oil type for best performance.

4. Clean or Replace Filters

• Fuel filter: Replace the fuel filter to remove potential clogs.

• Air filter: Clean or replace the air filter for proper airflow.

5. Bleed the Fuel System

If air has entered the fuel system, the generator may not start. To bleed the system:

• Open the bleed screws on the fuel injectors or fuel filter housing. 

• Pump the manual primer or power electric pump from the battery until fuel flows steadily without air bubbles.

6. Check Coolant Levels

Ensure the radiator or cooling system is filled with the appropriate coolant mixture. Low or old coolant can cause the generator to overheat during operation.

7. Test the Glow Plugs (for Cold Conditions)

If your generator has been stored in a cold environment, test the glow plugs. Faulty plugs may prevent the engine from starting. Replace them if necessary.

8. Turn the Generator On Safely

• Set the generator’s controls to “manual” or “start” mode.

• Crank the engine in short bursts to avoid overheating the starter motor.

• Allow the generator to idle for a few minutes after starting to circulate oil and stabilize.

Common Problems and How to Fix Them

If the generator doesn’t start after following the steps above, consider these troubleshooting tips:

Faulty Fuel Solenoid

A faulty fuel solenoid can prevent the engine from getting the diesel it needs. Test and replace it if required.

Clogged Magnetic Pickup

A dirty or faulty magnetic pickup can cause the engine to turn over but not start. Clean or replace it for better performance.

Stuck Valves

Idle periods can cause valves to stick. A professional mechanic can help address this issue.

Dead Alternator

If the alternator is not charging the battery, the generator may fail to start. Test and replace the alternator as needed.

Preventative Maintenance Tips

To avoid starting issues in the future:

• Run the generator monthly: Exercise it for 30 minutes to keep the engine lubricated and the battery charged.

• Use fuel stabilizers: Prevent fuel degradation with additives.

• Store in a dry location: Protect the generator from moisture and dust.

Why Is This Important for Businesses and Homeowners?

Diesel generators are often backup power sources for critical systems. Ensuring that they start reliably during emergencies is essential for preventing downtime and maintaining safety.

Final Thoughts

Starting a diesel generator that has been sitting for a long time requires a systematic approach to avoid damage. 

By inspecting and addressing common issues such as fuel degradation, battery failure, and lubrication problems, you can restore your generator to working order. 

Regular maintenance will ensure that your generator remains a dependable power source for years to come.

For more expert tips and advice on diesel generator maintenance, visit our blog at Sustainable Maintenance.