The Onan 5500 generator typically uses a two-cylinder gasoline engine, which means it generally has two spark plugs—one for each cylinder. This configuration is common in many portable Onan units designed for RVs, homes, and light industrial use. While two plugs is standard, variations can occur across different production years or model numbers, so it’s wise to verify by checking your specific unit’s service manual or model sticker.
Spark Plug Count for Onan 5500 Generators
In most Onan 5500 generators, you will find two spark plugs located on the engine block. The plugs are positioned to service each cylinder directly, ensuring reliable ignition for the dual-cylinder setup. If your unit seems to have more or fewer plugs, it may be a different engine configuration or a non-standard modification.
How To Identify Your Engine And Spark Plugs
To confirm the exact spark plug count on your Onan 5500, follow these steps: shut off the unit and disconnect from power, remove the outer housing to expose the engine, and locate the spark plug(s) on the cylinder head(s). Count the plugs and note their type and gap. If you’re uncertain, consult the owner’s manual or use the model number plate to reference the correct parts diagram from Onan or Generac.
Spark Plug Types And Replacement Intervals
Most Onan 5500 engines use conventional automotive-style spark plugs appropriate for small engines. Replacement intervals depend on operating conditions but commonly range from 100 to 300 hours of run time, or every season, whichever comes first. When replacing, use plugs specified in the manual or the parts diagram. Always gap the plugs to the manufacturer’s specification before installation.
Maintenance Tips For Optimal Performance
- Regular inspection: Check plugs for wear, fouling, or gap changes during routine service.
- Keep air clean: A clogged air filter can cause rich mixtures and plug fouling; replace or clean the filter as recommended.
- Use the correct fuel: Use fresh gasoline and appropriate stabilizers to prevent deposits that affect ignition.
- Correct torque: When installing plugs, snug to the manufacturer’s torque spec to avoid thread damage.
- Coil and wire checks: Inspect ignition wires and coil boots for cracks or corrosion that can cause misfires.
Common Symptoms Of Spark Plug Issues
Watch for hard starting, misfires, rough running, reduced power, or decreased fuel efficiency. If symptoms persist after replacing plugs, inspect ignition leads, coil packs, and the carburetor or fuel delivery system for underlying problems. Detergent or oil fouling on the plugs can indicate broader engine issues that require professional attention.
Where To Buy Replacement Plugs And Parts
Replacement spark plugs and gapping tools can be purchased through Onan/Generac dealerships, authorized service centers, or reputable online vendors. Always reference the model number of your generator to ensure compatibility. It’s often helpful to buy a small maintenance kit that includes a spark plug wrench, gapping gauge, and spare plugs for future service.