RV Generator Parts & Maintenance — Cummins Onan Filters, Kits & More
iFJF Direct is your one-stop shop for RV generator maintenance parts. From Cummins Onan filter kits to RV plumbing and appliances, we stock the parts that keep RV owners on the road and off the campground repair shop. Trusted by full-timers, weekenders, and fleet operators — our #1 selling category with US-based inventory and same-day shipping.
Cummins Onan Generator Parts — Our Specialty
The heart of any RV electrical system is the generator, and Cummins Onan powers more RVs than any other brand. We stock maintenance parts for every major Onan series, cross-referenced to OEM part numbers:
- QG 4000 / 5500 / 7000 — The most common RV generators. We carry oil filters (122-0836), air filters (140-2897), fuel filters (149-2513), fuel pumps (149-2341-01), spark plugs, and complete annual maintenance kits.
- Marquis Gold / Platinum — Older but widely used in Class A motorhomes. Filter kits, voltage regulators, carburetor rebuild kits, and ignition components.
- MicroQuiet 4000 — Compact generators for smaller RVs and toy haulers. Full filter sets, exhaust gaskets, and replacement fuel lines.
- KY / KYD Series — Entry-level generators. Oil change kits, air filter elements, and spark arrestor replacements.
Onan Generator Maintenance Schedule
| Service Item | Interval | iFJF Part |
|---|---|---|
| Oil & Filter Change | Every 150 hours | 122-0836 Oil Filter |
| Air Filter Replacement | Every 300 hours | 140-2897 Air Filter |
| Fuel Filter | Every 500 hours | 149-2513 Fuel Filter |
| Spark Plugs | Every 500 hours | 167-1637 Spark Plug |
| Fuel Pump Inspection | Annually | 149-2341-01 Fuel Pump |
Pro tip: Stock up on our complete maintenance kits to save 15-20% vs buying individual filters. One kit covers a full season of generator service.
RV Parts by Category
Appliances & Climate
Norcold and Dometic refrigerator control boards (N611/N811/N821), soft start kits for rooftop A/C units, water heater elements and thermostats (Atwood, Suburban), furnace ignitors and sail switches.
Plumbing & Water Systems
Dometic and Thetford toilets and replacement parts, Shurflo water pumps (2088/4008 series), PEX fittings and crimp tools, sewer hose kits with clear adapters, black tank treatments and rinse wands.
Electrical & Power
Automatic transfer switches (30A/50A), Progressive Industries surge protectors, battery disconnect switches, solar charge controllers (MPPT/PWM), LED interior and exterior lighting upgrades.
RV Generator Parts FAQ
How do I identify which Onan generator model I have?
Look for the data plate on your generator — typically located on the side of the unit or inside the access door. It will show the model number (e.g., 4KYFA26100K), spec letter, and serial number. The most common RV generators are the QG 4000 (4.0kW gasoline), QG 5500 (5.5kW gasoline), and QG 7000 (7.0kW gasoline). Diesel pushers commonly use the QD 7500/8000/10000 series. Match your model to our product listings for guaranteed fitment.
Can I use automotive oil filters on my Onan generator?
Technically yes — many Onan generators use the same thread pitch and gasket diameter as common automotive filters. However, we strongly recommend using OEM-spec filters like the 122-0836. Generator-specific filters have different bypass valve pressures and anti-drainback specifications optimized for small engine operating conditions (higher RPM range, frequent start/stop cycles). The cost difference is minimal compared to potential engine damage. Every iFJF filter is cross-referenced to the exact Onan specification.
What signs indicate my Onan fuel pump is failing?
The classic symptom is your generator starting, running for 10-30 seconds, then shutting down — this usually means the fuel pump cannot maintain fuel pressure. Other signs include: generator cranks but won't start, surging RPMs under load, extended cranking before firing, and no audible ticking from the pump when the generator is priming. The Onan fuel pump (149-2341-01) is a common replacement item, typically lasting 600-1,000 hours depending on fuel quality.
Do your Onan maintenance kits work for generator models outside RVs?
Yes — our Cummins Onan filter kits are compatible with Onan generators used in commercial trucks (APU), food trucks, emergency vehicles, mobile medical units, and construction equipment. The same QG and QD series generators power many non-RV applications. Filter specifications are identical regardless of the generator's installation environment. Just verify your model number against the fitment guide in each product listing.
Common Problems & Diagnosis: Troubleshooting Your Onan Generator
Onan generators are reliable workhorses, but no machine is immune to wear and age. Here are the most common failure patterns and how to diagnose them before they strand you at a dry-camping site:
Generator Cranks But Won't Start: The most frequent cause on gasoline models is stale fuel — fuel in the generator's carburetor bowl evaporates over time, leaving behind varnish deposits that clog the main and idle jets. If your generator has sat unused for more than 3-4 weeks, drain the carburetor bowl (most Onan carbs have a drain screw) and refill with fresh fuel. Add fuel stabilizer to your RV's fuel tank if the generator will sit for extended periods — especially important for ethanol-blended fuels that absorb moisture. Other causes include: a fouled spark plug (remove and check for wet, black, or eroded electrodes), a clogged fuel filter (149-2513 — try starting with starting fluid sprayed into the air intake to isolate fuel vs. ignition problems), or a failed ignition coil (test with an inline spark tester).
Generator Starts Then Dies Under Load: The generator fires up, runs smoothly at no-load, but stumbles or shuts down when the air conditioner compressor kicks on. This pattern points to one of three issues: (1) A clogged air filter (140-2897) — a restricted air filter causes an over-rich mixture that bogs under load. Remove the filter and test-run briefly; if the generator handles load without the filter, replace it. (2) A failing fuel pump (149-2341-01) — the pump can deliver enough fuel at low demand but cannot maintain pressure when the governor opens the throttle under load. (3) A slipping generator belt (if equipped) — inspect the belt connecting the engine to the generator head for glazing, cracking, or improper tension.
Generator Produces Power But Voltage Is Low or Flickering: The engine runs normally but lights dim and appliances cycle erratically. This is a voltage regulation problem: (1) The voltage regulator has failed — Onan regulators are sensitive to heat and vibration, especially on generators with high hours. (2) The brushes (on brushed generator heads) are worn past their service limit — remove and measure brush length against the specification in your service manual. (3) The slip rings on the rotor have accumulated carbon deposits from worn brushes — cleaning the slip rings with a commutator stone restores clean electrical contact. Any voltage irregularity should be addressed immediately — low voltage can damage your RV's air conditioner compressor (the most expensive appliance to repair) and refrigerator control boards.
Generator Surges or Hunts at Steady Load: RPM fluctuates up and down rhythmically even when the load is constant. This is almost always a governor or carburetor issue: (1) The governor linkage is binding or the governor spring has weakened — clean and lubricate all linkage pivot points with a dry-film lubricant. (2) The carburetor's idle circuit is partially clogged while the main circuit is clear — this causes surging when the governor transitions between the idle and main fuel circuits. (3) A vacuum leak at the intake manifold gasket or carburetor base gasket introduces unmetered air, leaning the mixture erratically. Spray carburetor cleaner around the intake joints while the generator is running — an RPM change indicates a vacuum leak at that location.
Buying Guide: Building Your RV Generator Spares Kit
Smart RV owners don't wait for a breakdown — they prepare for it. Here is how to build a generator spares kit that keeps you independent of repair shops:
Essential Spares (Carry These Always): (1) One complete oil change kit — oil filter (122-0836), 2 quarts of 15W-40 diesel oil (for QD series) or SAE 30 small-engine oil (for QG series), and a drain pan. (2) One air filter (140-2897) — air filters on generators operating in dusty campgrounds and unpaved roads clog faster than expected. (3) Two spark plugs (167-1637) — a fouled spark plug is the #1 field-repairable cause of generator no-start. (4) One fuel filter (149-2513) — small enough to carry and critical to generator operation. (5) A spare fuel pump (149-2341-01) — the fuel pump is the most common component-level failure on Onan generators and is easily replaced with basic hand tools.
Recommended Tools: Spark plug socket (13/16" or 5/8" depending on model), ratchet with 6-inch extension, 10mm and 12mm combination wrenches, inline spark tester, multimeter (for diagnosing voltage regulation and starting circuit issues), and a can of starting fluid (for fuel system diagnosis). A dedicated generator tool roll stored in the generator compartment ensures you have what you need when you need it.
Fuel Management: The single most important practice for generator reliability is fuel rotation. Run the generator under load (at least 50% rated capacity) for 30 minutes every month. This exercise burns the fuel in the carburetor bowl, circulates fresh fuel through the pump and lines, boils moisture out of the oil, and keeps the generator head's slip rings clean. Set a recurring calendar reminder — monthly exercise prevents 80% of the generator problems RV owners experience. For seasonal storage (3+ months), add fuel stabilizer, run the generator for 15 minutes to distribute stabilized fuel through the system, then drain the carburetor bowl.
Installation Tips: DIY Onan Generator Service
Onan generator maintenance is well within the capability of most RV owners with basic mechanical aptitude. These model-specific tips will make your service go smoothly:
Oil Change: Warm up the generator for 5-10 minutes before draining — warm oil flows faster and carries more contaminants. The drain plug is typically located on the bottom of the oil pan, accessible from underneath the generator. On some models, Onan provides a drain hose that extends to the edge of the generator tray for easier access. The oil capacity is small (typically 1.5-2 quarts) — add oil slowly and check the dipstick frequently to avoid overfilling. Overfilled oil causes crankshaft whip that aerates the oil, reducing oil pressure and potentially damaging bearings.
Air Filter Replacement: The air filter housing is typically secured by a single wing nut or spring clip. Before removing the old filter, vacuum or wipe away loose debris around the housing to prevent it from falling into the intake. If the filter foam pre-cleaner is present, wash it in warm soapy water, dry completely, then lightly oil it with foam filter oil (not engine oil — engine oil degrades the foam). A dry foam pre-cleaner does not trap fine dust effectively.
Spark Plug Replacement: Always use a spark plug socket with a rubber insert — a standard deep socket can crack the ceramic insulator. Gap the new plug to specification (typically 0.025-0.030 inches for Onan generators) before installation — factory pre-gapped plugs are sometimes knocked out of spec during shipping. Apply a small amount of anti-seize to the threads (keeping it off the electrode and insulator), thread in by hand to avoid cross-threading, then torque to specification (typically 15-20 ft-lbs). Over-tightening crushes the crush washer excessively and can strip the aluminum cylinder head threads — a $200+ repair for a $5 spark plug.
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