Onan 4000 and Seafoam for Surging/Revving on Startup

Harvester · 09-22-2022, 06:25 PM

On our 2020 Minnie Winnie 22R, we have the Onan 4000 generator. It's been pretty reliable, and I'm pretty good about starting it up about once a month. However, I had to let it sit in storage for two months during this summer in Texas heat while on a trip overseas. When I returned home, the next day I went to the RV storage and started the generator, and noticed that it was surging/revving for about the first 3-5 minutes. I then put it under load with the A/C, and it smoothed out after 5 minutes. Decided to visit the RV a couple more times over the next week, and the surging/revving now happens on each startup.

One other thing I should mention, is the carburetor was replaced under warranty by Cummins/Onan when I bought the RV new. It had apparently sat on the showroom floor for about a year, and no one started it up during that time. So its had a new carburetor since two years ago, and now has about 45 hours of run time.

In any case, consulted with YouTube and found several helpful videos using SeaFoam and a gallon of gas in a separate container. Disconnect the main fuel line, and run a fairly concentrated mixture of SeaFoam with premium gas (91 octane). All of the videos have different mix ratios, so I'm guessing it's not that critical to be exact. They run the generator for about 30 minutes, "hot soak", and then run it again for another 15-30 minutes.

As it would happen, I was on the phone to Lichtsinn RV talking to the service department about another topic, but brought my surging/revving issue up in the conversation. They suggested that on my next RV trip, run all the regular gas out of the fuel tank, and fill up with premium gas. Once I'm sure the tank has only premium, then add a can of SeaFoam. At that point, just run the generator for some period of time - maybe 30 minutes. Let it sit for a while, and then run another 30 minutes. Then after that, then just go back to filling up with regular gas.

This idea of just filling up with premium and pouring SeaFoam in the main gas tank would be easier. As it turns out, I'm planning about a 2000 mile trip pretty soon, and it's something I could do along the way. Of course I'll pay a bit more for fuel on those premium gallons of gas, but for the convenience of this alternative procedure would be worth it - if successful.

Before doing idea #2, I had some questions for the forum:

1. Are there any issues with running premium fuel and SeaFoam on the Ford V-10 engine? I should note that the engine has about 21K miles, and is running very good.

2. If the answer to the question above is no, what gas-to-SeaFoam ratio should I use? The gas tank has a 55 gallon capacity, but it seems like I should have something less than that.

3. Should I not consider this idea, and go with one of the YouTube video procedures?

Thanks!

Morich · 09-22-2022, 07:35 PM

Personal opinion as that is about all anyof us have to offer?
Considering the two spots where you got advise, I would definitely put the U-tube way down the list.
One place is a well know group who deals with this type question a lot. All it takes to make a video is a camera and lots of brass----knowledge not required!

I often think of the vid by the guy who made his own arc welder! He set a few things on fire and nearly killed himself but still posted the "advise" !

But they are both aiming the same thing from different directions, so they want to clear any deposits fouling small passages or combustion areas. That explains why there is no firm formula as there is no way to say how much you want to remove!
Kind of like how much scrubbing it takes to clean a bathtub? How dirty and what's on it!

For running higher test in the engine, it will not hurt it, in fact it may clear a few spots there and you may get better results there at the same time. The problem is if you find you like it so much you wish you used the high priced all the time!

I might go for less than a full tank and then just use the recommended amount from the bottle directions.

SgtB · 09-23-2022, 08:15 AM

Have heard and read a lot about this stuff, but have never used it in any of my engines, gas or diesel. Guess I have never had a reason to try it, as I do not store gas or diesel for long periods without an additive like Stabil. Any comments on it's usefulness beyond what this thread speaks to?

mduff · 09-25-2022, 07:19 AM

Echo Richards’s suggestion “ might go for less than a full tank and then just use the recommended amount from the bottle directions”, the amount of Seafoam for a full tank will be significant. The varying amounts of Seafoam to add are provided in the directions and depend on regular maintenance (10ml per litre) versus trying to fix an issue (15ml per litre).

Morich · 09-25-2022, 08:13 AM

Quote:

Originally Posted by SgtB

Have heard and read a lot about this stuff, but have never used it in any of my engines, gas or diesel. Guess I have never had a reason to try it, as I do not store gas or diesel for long periods without an additive like Stabil. Any comments on it's usefulness beyond what this thread speaks to?

I don't remember ever using that brand as there are several and I have used others but then it is one of those cases where we have two lines of thought!
Way back in history, I used a fair amount of time trying to clear bad carbs of gunk. For that I think we used transmission fluid poured slowly in the carb as we revved it.
Mostly it did clear some of the gunk out of the small passages and valves so things ran better but the neighborhood took a few hours to clear the smoke!

Finally it occured to me that I could save a lot of trouble if I just kept things from getting that gunk in the carb! DUH!

So when I store things, I add something to keep the gunk from happening and Stabil is the one I use most.

One good reason to exercise the genset more often? I see ads telling me the really low hours on the generator as if that was a good thing? Really just tells me the thing may not run very well as it is likely to be gunked up!

Harvester · 09-26-2022, 07:21 PM

Here is a link to a PDF from SeaFoam explaining the procedure for RV generator cleaning. They essentially recommend a gas can/hose method:

https://seafoamworks.com/uploads/201...ose-Method.pdf

I'm continuing to exercise the generator in the meantime, and ran it for over an hour yesterday, stopping at 30 minutes and starting again. On the first startup, it revved for about 3 minutes, and became stable after that. I ran it under load with the A/C. On the second startup, it ran smooth from the beginning.

We're planning a trip to Big Bend National Park this weekend, and plan to exercise the generator - likely every day. When we get back, I'll be doing my annual oil change on the Onan 4000. Since that's already on the agenda, will consider doing the SeaFoam method from above link, if the generator hasn't improved from the repetitive exercising.

Thanks for the replies, and I'll update this thread with my experiences and process as they unfold.

Thanks again!