Well, I've officially joined the 'I should have winterized properly' club! Left our 2017 Winnebago Travato 59K with its Onan Cummins HGJBB 2.8 generator sitting for almost a year (oops), and now it's throwing a tantrum. It's running rougher than a shopping cart with a wonky wheel, and the moment I try to put any load on it - like actually using it for something useful - it just gives up and dies on me.
I removed the carburetor, and my friend helped me clean it in a sonic cleaner. Now I'm stuck because I'm not sure if the throttle and choke linkage are correctly positioned when I reinstalled it. I've confirmed fuel is getting to the carburetor, but it won't start. I took some pictures showing the wire connections and mounting, hoping someone can help me figure out the precise linkage setup.
I'm pretty sure I know what's wrong (thanks, old gas and my laziness with fuel stabilizer), but I'm wondering if anyone can confirm my suspicions about what happens to these carburetors when they sit with stale fuel. Is this the classic 'your carburetor is now a museum of varnish' situation? And if so, what's the real deal on getting it cleaned up and running again?
Year of storage without stabilizer causes carburetor varnish. Carburetor needs thorough cleaning or rebuild - soaking, jet cleaning, new gaskets. Running rough and stalling under load are classic symptoms of blocked jets from old fuel residue.
Your Onan HGJBB 2.8 generator uses electronic fuel injection (EFI), not a carburetor. The rough running and starting issues after storage are likely related to fuel system problems, clogged fuel injectors, or EFI system faults rather than carburetor linkage issues. This generator has a throttle body assembly that controls airflow, but fuel delivery is managed electronically. The good news is that you was right about the easy removal - these HGJBB units in the 2017 Travato 59K are accessible from underneath, and the carburetor linkage setup is actually fairly straightforward once you understand the connections.
Since you mentioned the generator was getting fuel but won't start after reassembly, the issue is likely related to the EFI system, throttle body position sensor, or fuel injection components rather than choke systems (which don't exist on EFI engines). The plastic arm lock you referenced in your photo is likely the throttle control linkage, and there should be a separate wire or linkage for the choke system.
Carburetor linkage problems after cleaning are incredibly common because there are multiple connection points that need to be reassembled in the exact right sequence and position. On your HGJBB 2.8, the throttle linkage connects the governor system to the carburetor throttle shaft, while the choke system has its own separate actuator. When these connections aren't properly aligned, the generator's control system can't properly manage the air-fuel mixture during startup and operation.
Extended storage without fuel stabilizer can cause fuel system problems in EFI generators, including clogged fuel injectors and fuel line deposits. However, since your HGJBB 2.8 uses electronic fuel injection, there are no carburetor jets or choke linkages to clean or adjust. Even being off by a few degrees on the throttle shaft position can prevent the engine from getting the right amount of air during startup.
The challenge with working under the van is that you can't easily see the reference marks or positioning that would normally guide proper reassembly. Most technicians who work on these regularly know exactly how the linkages should look when properly connected, but without that visual reference, it's easy to get things crossed up.
You'll need a basic tool set including screwdrivers, needle-nose pliers, and a small flashlight or headlamp for better visibility under the van. More importantly, you'll want to download the service manual for your specific HGJBB 2.8 from Cummins' website - it has detailed diagrams showing the correct linkage positions. If possible, get a friend to help so one person can work the linkages while the other observes the carburetor throttle and choke plates.
Before making any adjustments, take several clear photos of the current linkage setup from different angles, even if they're not perfect. These will help you return to the current position if needed. Have some aerosol carburetor cleaner on hand in case you need to clean any connections, and avoid using starting fluid since you've confirmed the generator is already getting fuel - focus on linkage adjustment instead.
Safety-wise, make sure the generator is completely cool, ensure you have adequate ventilation when working. Position yourself comfortably under the van with proper support - you'll likely need to make several small adjustments while testing, so comfort matters for precision work.
Start by locating the throttle body assembly - it should have electronic connections and a throttle position sensor. With the generator off, the throttle plate in the throttle body should be in its default position. Note that this is an EFI system, so there is no carburetor throat or traditional carburetor components. The plastic arm lock you mentioned should be connected to this throttle linkage system, and when properly adjusted, it allows the governor to control engine speed under load.
The HGJBB 2.8 uses electronic fuel injection and does not have a choke system. Cold start enrichment is handled electronically by the EFI system. Look for electrical connections to the throttle body, fuel injectors, and engine control module rather than mechanical choke components.
To test your current setup, have someone turn the key to the start position while you observe both the throttle and choke operations. The choke should close completely, and the throttle should open slightly (not wide open, but more than the idle position). If neither is happening correctly, you'll need to adjust the linkage connections. Start with the throttle linkage first - disconnect it and check that it moves freely through its full range, then reconnect and adjust the linkage connection point for proper throttle opening during start attempts.
If the engine fires with starting fluid and manual throttle control, your throttle linkage just needs proper adjustment. Reconnect the linkage and adjust the connection point until you get the right throttle opening during start attempts. For the choke, if it's not closing properly, check that the linkage isn't binding and that any electrical connections are clean and tight. The goal is to have both systems working in coordination - choke closed and throttle slightly open for starting, then choke opening and throttle responding to the governor as the engine warms up.
If you've tried the linkage adjustments and the generator still won't start, there might be internal carburetor issues that the sonic cleaning didn't resolve. Sometimes the small passages in the carburetor require more aggressive cleaning or replacement of internal components like the float, needle valve, or jets. At this point, you'd be looking at either a complete carburetor rebuild (which requires special tools and expertise) or replacement with a new unit.
The $650 quote for a new carburetor is actually reasonable for OEM Onan parts, though you might find aftermarket options in the $300-400 range. However, before going that route, consider having a small engine shop or generator specialist take a look at your cleaned carburetor - they might be able to complete the rebuild for $150-250, which would be much more cost-effective than replacement.
Another option is to contact an RV mobile service technician who specializes in generators. Many of these techs have worked on Travato installations specifically and can usually sort out linkage issues quickly. The service call might run $150-200, but they'll have the experience to get your generator running properly and can advise whether your carburetor cleaning was sufficient or if additional work is needed. Given that you've already saved the $400-500 in labor costs by removing and cleaning the carburetor yourself, having a professional handle the final adjustment might be a smart investment to get back on the road reliably.
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