Generators are the unsung heroes of countless RV adventures, job sites, and emergency preparedness plans. And when you're relying on a workhorse like the Onan 5500, understanding its Onan 5500 Generator Parts, Accessories & Upgrades isn't just helpful – it's crucial for maximizing its lifespan and ensuring reliable power when you need it most. This isn't just about fixing things when they break; it's about smart maintenance, informed choices, and even enhancing your generator's capabilities.
Consider this your comprehensive guide, meticulously crafted for the Onan 5500 owner who values dependability and wants to know the ins and outs of their power plant. We’ll delve into everything from the spark plugs that kickstart your day to the specialized components that keep it humming efficiently, whether it’s fueled by gasoline, EFI, or LP gas.

At a Glance: Your Onan 5500 Essentials

  • Routine Maintenance is Key: Regular checks and replacements of air filters, oil filters, fuel filters, and spark plugs are non-negotiable for longevity.
  • "Spec" Matters: Your generator's specific "Spec" (e.g., A, B, J, K) is vital for ordering correct parts, especially for fuel systems and controls.
  • Fuel Type Dictates Parts: Carbureted, EFI, and LP gas models have distinct fuel system components; don't mix and match.
  • Engine Overhaul Options: From piston rings to entire replacement engines, options exist to breathe new life into your unit.
  • Strategic Upgrades: Beyond basic repairs, consider enhancements like better mounting solutions or even remote monitoring.
  • Original vs. Aftermarket: Weigh the benefits of genuine Onan parts for guaranteed fit and performance against third-party alternatives.
  • Documentation is Your Friend: Always consult your generator's manual and note down your model and spec number before ordering.

The Heart of Reliability: Why Your Onan 5500 Deserves Attention

The Onan Marquis Gold 5500, particularly models like the 5.5HGJAB, has earned its reputation as a robust and reliable power source. But like any sophisticated machinery, it thrives on proactive care. Ignoring the signs of wear or postponing crucial maintenance can quickly turn a minor fix into a costly repair. Understanding the components that make up your Onan 5500 empowers you to diagnose issues, perform routine maintenance, and make informed decisions about repairs and upgrades.
When it comes to keeping your generator in top shape, think of it as a finely tuned engine – because it is! From the smallest O-ring to the largest stator, each part plays a critical role in producing the consistent power you rely on. If you're looking for an even broader overview, you can explore All about Onan 5500 generators.

Essential Maintenance Parts: Keeping Your Onan 5500 Gold Running Strong

Think of these as the lifeblood of your generator. Regular replacement prevents breakdowns, maintains efficiency, and extends overall life. Don't skimp here.

The Filters: Air, Oil, and Fuel

These are your generator's first line of defense against contaminants.

  1. Air Filter: The ONAMAX 30W - QUART AIR FILTER is designed to protect your engine from dust and debris, ensuring clean airflow for proper combustion. A clogged air filter chokes your engine, reduces power, and increases fuel consumption. Check it regularly and replace it when dirty.
  2. Oil Filter: Part number 140-3116, this filter keeps your engine oil clean, preventing harmful particles from circulating and causing premature wear. Always replace the oil filter whenever you change the engine oil.
  3. Fuel Filter: Whether you have a carbureted or EFI model, a clean fuel filter (P/N 149234101 for many carbureted models, or specific EFI fuel filters) is paramount. It prevents impurities in your fuel from reaching and damaging delicate components like carburetors or fuel injectors.

Spark Plugs: The Ignition Point

The spark plug (P/N 167-1638) is where the magic happens, igniting the air-fuel mixture. Ensure yours are gapped correctly at 0.60MM for optimal performance. Worn or improperly gapped plugs lead to misfires, rough running, and reduced fuel efficiency. Keep a spare set on hand.

Oil: The Lubricant of Life

While not a "part" in the traditional sense, engine oil is arguably the most critical consumable. Always use the grade recommended by Onan, often a quality 30W or multi-viscosity oil, ensuring it meets the specified API service category. Regular oil changes, coupled with a new oil filter, are the single best thing you can do for your engine's longevity. Remember, proper lubrication prevents friction, dissipates heat, and cleans internal components.

Diving Deeper: Engine Component Replacements

Sometimes, simple maintenance isn't enough, and you need to look at internal engine components. The Onan 5500 engine is serviceable, offering options from minor repairs to complete overhauls.

Top-End Overhaul: Cylinder Heads, Valves, and Gaskets

The cylinder head assembly, including intake and exhaust valves, springs, and seals, is crucial for combustion. If you notice a loss of compression, excessive oil consumption, or unusual smoke, a top-end refresh might be in order. Parts like cylinder heads (1 & 2), guides, studs (M8X1.25X30), and valve seals are available. Don't forget the specialized rocker cover and cylinder head gaskets for a tight seal. An overhaul kit, including O-rings for the stator housing (P/N 5090420), is a smart purchase for comprehensive work.

Bottom-End: Crankshaft, Pistons, and Rods

These components form the core moving parts of your engine.

  • Crankshaft and Bearings: The crankshaft, along with its main bearings and oil seals, converts the piston's linear motion into rotational energy.
  • Pistons and Rings: Pistons come in standard, 0.25 oversize, and 0.50 oversize options, complete with piston rings and pins. These are critical for creating compression and transferring power.
  • Connecting Rods: These link the pistons to the crankshaft, requiring specific bolts for secure attachment.
    If your engine exhibits severe knocking, excessive oil consumption not solved by a top-end repair, or complete failure, a bottom-end rebuild might be necessary.

Camshaft and Valvetrain

The camshaft assembly precisely times the opening and closing of your intake and exhaust valves. Components include the camshaft itself, tappets, valve springs, collets, retainers, push rods, rocker arms, pivot bolts, pivot nuts, and guide plates. Issues here can lead to poor engine performance and misfiring.

Replacement Engines: EFI vs. Carbureted Options

For significant engine damage, a full replacement engine might be the most practical solution. These are available in both EFI (Electronic Fuel Injection) and Carbureted versions, with or without a PTO (Power Take-Off). Upgrading from a carbureted to an EFI engine can offer improved fuel efficiency, easier cold starts, and better performance at varying altitudes, though it requires a more significant investment and potentially additional control system modifications. You can read more about various aspects of these generators in our comprehensive guide, All about Onan 5500 generators.

Fueling Your Power: Understanding Onan 5500 Fuel System Parts

The Onan 5500's fuel system varies significantly based on whether it's carbureted, EFI, or LP gas. Identifying your generator's specific configuration is paramount for ordering the correct parts.

Carbureted Systems: The Classic Approach

For models running on gasoline with a carburetor, you'll encounter components like:

  • Carburetors: Specific part numbers exist for different specs (e.g., Spec J, Spec K superseded by A062T422) and high-altitude applications. The main carburetor (P/N 5410765) is a common replacement item.
  • Gaskets and Insulators: Intake manifold gaskets and carburetor gaskets/insulators are essential for preventing air leaks and ensuring proper fuel-air mixing. The intake manifold (P/N 154-3067-03) is also available.
  • Fuel Pumps: Mechanical or electric fuel pumps (superseded by A064S965, A047N929) deliver fuel from the tank.
  • Fuel Solenoid Cutoffs: These prevent fuel flow when the generator is off, often a common point of failure causing starting issues.
  • Choke Kits: Choke kits (A043B658) assist with cold starts.
  • Fuel Filters: As mentioned, (P/N 149234101) is common.

EFI Systems: Modern Efficiency

Electronic Fuel Injection systems offer superior control and efficiency. Key parts include:

  • Throttle Body Assemblies: (P/N 146-0782-S0) regulate airflow.
  • Fuel Rails and Injectors: Deliver precisely metered fuel into the engine. Fuel injectors come with O-rings for proper sealing.
  • Sensors: MAP (Manifold Absolute Pressure) and Manifold Air Temperature sensors provide critical data to the ECU (Engine Control Unit) for optimal performance.
  • Fuel Pressure Regulator: (P/N 148-1337) maintains consistent fuel pressure.
  • EFI Fuel Filters: Specific filters for higher pressure EFI systems.
  • Remote Fuel Pump Kit: For certain EFI models (e.g., 600, 1273, 97, 1276), a 15-foot harness remote fuel pump kit is available, enhancing fuel delivery options.

LP Gas Systems: Propane Power

Onan 5500 generators can also run on LP (liquid propane) gas, featuring a distinct set of components:

  • Mixers: Various P/Ns exist for HGJAA, HGJAB, HGJAC models.
  • Converters (IMPCO): Crucial for converting liquid propane to a gaseous state.
  • LP Fuel Filters: (P/N 149-2648) specific for propane.
  • Regulator Assemblies: (P/N 148-1131-S0) manage gas pressure.
  • Shutoff Solenoid Assemblies: (P/N 307-2938-S0) control LP gas flow.
    When troubleshooting fuel issues, always start by confirming your fuel type and generator specification, as this will narrow down the relevant parts list considerably.

Power Delivery & Control: Generator, Drive, and Electrical Components

Beyond the engine, a significant portion of your Onan 5500 is dedicated to generating and controlling electricity.

Flywheel & Drive System: The Mechanical Link

This system transfers power from the engine to the generator head.

  • Flywheel Assemblies: Crucial for engine balance and power transfer.
  • Drive Pulley Assemblies: With bearings, these transmit power via belts. Note that these and bearing sleeves are distinct for Spec A & B versus Begin Spec C.
  • Belts: Specific belts are used for 5.5KW models and different ones for 6.5KW & 7.0KW models. Using the correct belt ensures proper tension and longevity.
  • Generator Fans & Backplates: (e.g., A030C572 for fan backplates) keep the generator cool.
  • Tensioner Components: Bushings (190-0754), springs, and tensioner arm assemblies with pulleys (190-0758-S0) maintain correct belt tension.

Governor System: Precision for Stable Power

The governor system meticulously controls engine speed to maintain a consistent electrical frequency (e.g., 60HZ). Components include the shaft, lever, needle bearing, tension spring, throttle link, governor lever, and specific governor springs for 7.0KW 60HZ (Gold) and 5.5KW 60HZ (Silver) models. A malfunctioning governor can lead to unstable voltage or frequency, damaging sensitive electronics.

Rotor, Stator, & Brushes: The Electricity Makers

These are the core of the generator head itself.

  • Stator: (5.5KW 80MM, P/N 220-4544-S2) the stationary part where electricity is induced.
  • Rotor: (5.5KW, P/N 201-3638-01) the rotating part, including bearings and a collector ring. Rotor/stator kits (80MM, Spec A-G) are available for comprehensive replacement.
  • Brush Blocks, Generator Brushes, and Springs: These transfer current to the rotor. Worn brushes are a common cause of no-output issues and are usually simple to replace.

Control Systems: PCBs, Switches, Circuit Breakers, and Harnesses

This is the brain and nervous system of your generator.

  • Control Covers and Switch Covers: Protect the delicate electronics.
  • PCB Control / Control Cards: (e.g., PCB for Spec A-E, control card for Begin Spec J) these are the main circuit boards that manage generator operation, safety shutdowns, and diagnostics.
  • Rocker Switches: For start/stop and other functions.
  • Circuit Breakers: (30/30AMP, 20AMP, 25/25AMP) protect your generator and connected devices from overcurrents. Always replace with the correct amperage.
  • Engine Harnesses: Detailed harnesses with specific connectors (e.g., 23-pin P1, 8-pin J2), terminals, housings, seals, and fuses (7.5 AMP) connect all the electrical components. These can be complex, and specialized tools may be needed for repair.
    Understanding these components can help you diagnose electrical issues and ensure the safe operation of your Onan 5500. For more detailed information, especially regarding your specific model, refer back to All about Onan 5500 generators.

Exhaust System: Keeping it Quiet and Clean

The exhaust system manages hot, noxious gases, and significantly impacts noise levels.

  • Exhaust Manifolds: (e.g., A026H890 for Spec A-E, Begin Spec J) channel exhaust gases. Different manifolds exist for unhoused HGJAC models.
  • Exhaust Manifold Shields: For HGJAA & HGJAB models, these protect surrounding components from heat.
  • Exhaust Manifold Gaskets and Insulation: Essential for a leak-free seal and heat management.
  • Exhaust Baffles: (A030C565) specific for LP Vapor/Gasoline and LP Liquid models, these help reduce noise.
  • Mufflers: Different mufflers are listed for HGJAA and HGJAB to dampen sound.
  • Exhaust Installation Kits: Various kits (front outlet, rear outlet, side mount front/rear outlet) allow for flexible mounting options in different applications.
  • Exhaust Silencers and Temperature Sensors: Further enhance noise reduction and monitor critical temperatures.
    A healthy exhaust system isn't just about noise; it's about efficient engine operation and preventing dangerous carbon monoxide leaks.

Beyond the Basics: Accessories and Strategic Upgrades

While parts focus on repair and maintenance, accessories and upgrades enhance functionality, protection, and user experience.

Enclosure Parts: Protection and Sound Dampening

  • Generator Enclosure and Cover: (P/N 405-6915-01 black, green complete; cover P/N 405-6916-01) These protect the generator from elements and contribute significantly to noise reduction. They vary by specification.
  • Door Assemblies: (Spec A P/N 405-6601; Spec B-E P/N 405-6918-01 black) allow access for maintenance.
  • Insulation: Specialized insulation further reduces operational noise.
    Replacing damaged enclosure parts not only restores aesthetics but also crucial protection and sound attenuation.

Mounting Solutions: Underfloor Kits

For RV applications, underfloor mounting kits (405-6698, 405-6699 for HGJAA & HGJAB) are popular accessories. These kits securely position the generator, often reducing vibration and optimizing space. Proper mounting is essential for safety and performance.

Practical Upgrades

While specific "performance" upgrades for an Onan 5500 are limited, consider:

  • Remote Monitoring Systems: If not already equipped, adding a remote panel or even a smart monitoring system allows you to check status, start/stop, and receive alerts without going outside.
  • Advanced Fuel Filtration: For carbureted units, ensuring you have the highest quality fuel filter and routinely draining condensation from the tank can prevent many common fuel-related issues.
  • Enhanced Soundproofing: While the enclosure helps, additional sound-dampening materials can further reduce noise, especially in sensitive environments.

Deciphering Labels & Documentation

Don't underestimate the power of documentation. Your generator will have various labels, including logos, warning labels (installation, operation, fan, B-), caution labels (overheat), and fuel labels (side, supply, return). These are vital for safe operation and identification. Always replace illegible or missing labels.
When you're ready to make a purchase or delve deeper into your generator's specifics, remember that All about Onan 5500 generators is a valuable resource.

Navigating the Onan Ecosystem: Tips for Sourcing Parts

Finding the right part can feel like a maze, but armed with the right information, it's straightforward.

The Importance of Your Spec Number (A-L)

This cannot be stressed enough. Your Onan 5500 model number, followed by its "Spec" (e.g., 5.5HGJAB-1234A, where 'A' is the spec), dictates which parts are compatible. Many fuel system components, control cards, and even some engine components differ significantly between Specs. Always have your full model and spec number ready when looking for parts.

Authorized Dealers vs. Aftermarket

  • Authorized Onan Dealers: The safest bet for genuine OEM (Original Equipment Manufacturer) parts. You're guaranteed fitment, quality, and often, a warranty. They also have access to the latest parts lists and supersession information (when an old part number is replaced by a new one).
  • Aftermarket Suppliers: Can offer more budget-friendly options. Quality varies widely, so research reputable brands. Be cautious with critical components where precise fit and material quality are paramount.

Verifying Part Numbers and Supersessions

Always double-check part numbers against your generator's service manual or a reliable online parts catalog using your full model and spec number. Onan, like other manufacturers, often "supersedes" old part numbers with new ones. A dealer or good online resource will be able to cross-reference these for you.

When to Consult a Professional

While many routine maintenance tasks and basic part replacements are DIY-friendly, don't hesitate to call a certified Onan technician for:

  • Complex engine rebuilds or diagnostics.
  • Electrical system troubleshooting beyond basic circuit breaker checks.
  • Fuel system issues that require specialized tools or knowledge, especially with EFI or LP gas systems.
  • Safety-critical repairs.
    A professional can prevent costly mistakes and ensure your generator is running safely and efficiently.

Common Questions About Onan 5500 Parts & Maintenance

We hear these questions often. Here are some quick, clear answers:
Q: How often should I change the oil and filters on my Onan 5500?
A: Generally, Onan recommends changing the oil and oil filter every 150 hours or annually, whichever comes first. Air and fuel filters should be inspected regularly and replaced as needed, or at least every 150-300 hours depending on operating conditions. Always check your specific owner's manual for precise intervals.
Q: Can I upgrade my carbureted Onan 5500 unit to EFI?
A: While technically possible, it's a significant undertaking. It would require a new EFI engine, throttle body assembly, sensors, fuel rail, injectors, EFI fuel pump, and a compatible control system (ECU/control card). The cost and complexity usually make it impractical compared to simply buying a new EFI generator if that's your primary goal.
Q: What do I need for high-altitude operation?
A: For carbureted models, a specific high-altitude carburetor or re-jetting kit is often required to adjust the air-fuel mixture for thinner air. EFI models typically adjust automatically via their sensors and ECU, making them more adaptable to altitude changes without user intervention.
Q: How do I find my generator's 'Spec' number?
A: The full model and spec number are usually located on a data plate or label on the generator itself, often near the control panel or on the side of the enclosure. It will look something like "5.5HGJAB-1038A" where the "A" at the end is the spec. This is critical for accurate part identification.

Your Path to Peak Performance: Final Thoughts

Your Onan 5500 generator is an investment in convenience and security. By taking a proactive approach to understanding its parts, accessories, and potential upgrades, you're not just ensuring its immediate functionality; you're preserving its long-term value and reliability. From the humble spark plug to the intricate control board, each component contributes to a powerful symphony that keeps your lights on and your adventures powered.
Regular maintenance, using genuine or high-quality replacement parts, and knowing when to seek professional help are the cornerstones of responsible generator ownership. Empower yourself with this knowledge, and your Onan 5500 will continue to be a dependable companion for years to come.