Watt’s Up

Photographer: Chris Hemer


Learning how to properly maintain a built-in or portable generator can save time, trouble and money


As a trailer owner, it probably took you only a few camping trips in the boonies to realize that your home on wheels wasn’t really designed for long-term camping without electrical hookups. Hey, you’ve got a battery (or two), right? How much power could a few lights and a refrigerator take, anyway? As it turns out, quite a bit. And if your trailer is outfitted with all the comforts of home, like a microwave, television and air conditioning, they’ll be little more than electronic paperweights without a steady supply of 120-volt AC power from a humble generator.

Whether you power up with a small portable unit or own a toy hauler or fifth-wheel with a built-in model, you rely on a generator every time you camp off the beaten path. Yet, paradoxically, most of us don’t maintain our generators properly. You wouldn’t think about buying a tow vehicle, driving it a few miles each summer and then ignoring it for the rest of the year, but that’s precisely what a lot of RVers do. A generator is comprised mainly of an engine — one that shares a lot of similarities with other engines including a carburetor (or a venturi in LP-gas generators), air and oil filters, belts and other components. You may have grown accustomed to that power plant roaring to life whenever you pull the cord or push the Start button, but all it takes is a few months of neglect, and your generator could go on strike when you need it most.

To get some expert advice on generator maintenance, we visited Smith Powerhouse, Inc. in Bellflower, California, a factory-authorized service and warranty center for Cummins Onan, Honda, Kohler and Generac generators. Owner David Voloshin and shop foreman Matt Rudametkin are certified master generator technicians who have nearly 50 years of experience between them, and they’ve seen it all.

By far the most common built-in RV generators in use today are the 4,000-watt Cummins Onan (known as the MicroLite 4000, MicroQuiet 4000 and RV QG 4000), its 3,600-watt LP-gas variant (MicroLite, MicroQuiet and RV QG 3600 LP) and the larger Cummins Onan Marquis Gold 5500 and 7000 (also known as the RV QG 5500 and RV QG 7000), and their propane counterparts, the Marquis Gold/RV QG 5500 LP and 6500 LP, so these will be the focus of this article. There are a lot of good choices for portable generators as well, but from our experience, the most popular model among RVers is the 2,000-watt Honda EU2000i, so we’ll be covering maintenance tips on this model as well.

Now, while the most frequent types of maintenance, such as oil/filter and spark-plug changes, shouldn’t prove too challenging for most DIYers (and can save some time and money), Smith Powerhouse recommends against more advanced maintenance procedures for two important reasons. One, you will likely do more harm than good if you don’t know exactly what you are doing, and two, you can seriously hurt yourself. When it comes to major scheduled maintenance, it’s best to leave the heavy lifting to experts like Smith Powerhouse.

With all that said, let’s take a closer look at what makes our favorite generators tick.

Cummins Onan MicroLite, MicroQuiet and RV QG 4000/3600 LP

generators-0046 1) This is what most of us are familiar with when we open the generator compartment door: a plastic box that tells us little or nothing about its inner workings. But the popular Onan 4,000-watt gas generators are actually very easy to service — start by turning the two black levers to release the front cover.
 2) The Cummins Onan 4,000-watt generator is a single-cylinder, air-cooled engine designed to run on gasoline. Above the Start/Stop switch (A) is the carburetor (B), which is fitted with a mixture screw (C) at the bottom to allow limited adjustments for altitude. The cover emblazoned with “Onan OHV” is the valve cover. Bottom right is the yellow oil filler/dipstick (D). Note the large brush assembly (E); this acts as a gasket to compartmentalize the engine components when the cover is in place, promoting proper airflow from the fan (at left, not visible) over the critical engine components. It is for this reason that you should never run the generator with the cover off, even in very hot weather. Make sure you have the ID tag info (F) on hand when ordering parts.
generators_0147 generators-0053
  3) The Cummins Onan RV QG 3600 is functionally identical to the MicroLite/MicroQuiet/QG 4000 generator, except that it runs on LP-gas. On the upside, LP-gas-powered generators don’t suffer from a gummed up carburetor if allowed to sit for long periods. On the downside, they don’t produce as much power as their gasoline-burning counterparts, which is why they are derated somewhat. With the covers off, you can see the venturi (A), which functions similarly to a carburetor, and the LP regulator (B).  4) Checking the oil is similar to any other engine; unscrew the cap and note the level. If the generator has been properly maintained and the oil has been changed at the recommended intervals, it should be brown like this, not dark brown or black.
5) Before changing the generator’s oil, run it for at least 10 minutes to get it up to operating temperature, which helps the oil drain easily and completely. Trailers factory-equipped with a generator like this one (or even generator prep) will have an access panel underneath the generator compartment. Simply remove the two screws, and the drain plug will be exposed.  generators-0048
6) Remove the plug and allow the oil to drain into a suitable container. Cummins Onan 4000/3600 LP generators hold only 1.7 quarts of oil, so this process goes pretty quickly. This generator doesn’t use an oil filter, so all you have to do now is replace the drain plug and access panel, and refill the crankcase with the recommended oil.

7) The air filter housing is also clearly labeled, and the element is very easy to inspect/replace. Simply remove the wing nut on the side of the housing, then remove the wing nut that holds the filter in place. The filter can then be pulled free. This one still looks in good condition; a filter in need of replacement will be a dark color. When replacing the filter, be sure to reinstall both wing nuts, not just the one on the housing, or the filter will not be seated properly and will not clean incoming air.

8) To the right of the yellow oil filler is a gray (in this instance) or black spark plug cover boot. Pull it down, and the end of the engine’s single spark plug will be revealed. The plug can then be removed with a common spark-plug wrench and inspected/replaced.
 9, 10, 11) These gas generators also come equipped with a small fuel filter that should be replaced periodically according to the maintenance schedule. Remove the fuel hose clamp (arrow) first, then pull the hose off the filter barb. Next, pull the rubber gasket out of its groove to gain access to the filter. The filter assembly is threaded and can be easily removed with a 9/16-inch-deep socket.

12) An inexpensive upgrade Smith Powerhouse recommends is a second fuel filter (routed inline in an accessible location) to further ensure against dirt and grit entering the fuel system.

13) The most common cause of hard starting (or not starting at all) with an RV generator is lack of use. Smith Powerhouse recommends that you run your generator every four weeks for two hours under load (such as a running air conditioner) to keep it properly exercised. The discoloration at the bottom of this carburetor float bowl means that fuel sat there for several months, and the deposits clogged the tiny orifices in the carburetor. Once allowed to deteriorate to this point, you’re looking at a $300 bill for the carburetor, plus removal/replacement labor. If running the generator regularly isn’t an option, Smith Powerhouse recommends installing a shutoff valve in the fuel line before the generator. Turn the valve off, then run the generator until it is out of fuel. Adding a fuel stabilizer (like Onan OnaFresh) is also recommended.

14) Don’t forget that the generator is more than just an engine — it’s a power-generation system. Letting it sit for long periods can also cause the brushes to stick and the slip ring (shown) to oxidize, causing any number of power-delivery issues. This damage is not easily repairable and will more than likely require the attention of a professional.
 15) The Cummins Onan 4,000-watt gas/3,600-watt LP generator uses an overhead valve engine complete with valve springs and rocker arms. Valve clearance is adjusted in similar fashion, with a pair of wrenches and a feeler gauge. However, neither Smith Powerhouse nor Cummins Onan recommends you try this yourself. For one thing, valves that are too tight or loose will cause engine damage. Plus, an accidental bump of the starter can mean serious injury.

16) Wherever you take your generator for service or troubleshooting, Smith Powerhouse recommends you ask the shop personnel if they have a load bank. Similar to a dynamometer for cars, a load bank can load the generator to different percentages to make sure it’s running properly and producing the correct frequency, amperage and voltage for a given load. Smith Powerhouse conducts this test with every generator it services.


Cummins Onan
Marquis Gold/RV QG 5500 and 7000, 5500 LP and 6500 LP

 1) Other popular Cummins Onan generators are the gas-powered 5,500- and 7,000-watt models (typically found in larger toy haulers) and the 5500 LP/6500 LP found in some fifth-wheels. This is a V-twin engine oriented on its side, with the valve covers facing up (the right cylinder is visible). Though it is a completely different design from the 4,000-watt generators, many maintenance procedures are similar. Note that the oil fill/dipstick is in the same location as the 4000/3600 LP.

2) The air cleaner uses a paper element that is readily accessible from the front of the unit. Simply unsnap the clips, and the cover comes right off. This filter element still looks good.
3) Draining the oil on the 5500 and 7000 is simple, since it uses a petcock instead of a drain plug. Warm the engine for about 10 minutes, then put a pan underneath and open the petcock; the oil is routed underneath the RV through a rubber hose.  generators-0113
 generators-0114-crop 4) Unlike its smaller brother, the Marquis Gold 5500/7000 does have an oil filter (arrow) that looks like a small automotive filter. It is accessed through a hole in the bottom of the generator compartment. Both the replacement filter and handy wrench are available through Cummins Onan dealers.
5) The Marquis Gold 5500/7000 has its spark plugs oriented on the sides of the cylinders (arrow), which can make them a challenge to reach. A swivel socket does the trick here. Removing the left (or Number 1) cylinder spark plug requires the removal of the air-filter assembly first.  generators-0115-crop
 generators-0118  6) Depending on the year and model, the 5500/7000 gas generators may actually have two fuel filters: this secondary one, near the carburetor, and a primary one at the fuel pump. Be sure to inspect your particular generator to see if it has two; replacing one won’t do it.


Honda EU2000i


 1) The popular Honda EU2000i portable generator is not only reliable but easy to service. Popping off the front cover reveals the air-filter housing (A), carburetor (B) and oil fill/dipstick.

2) Removing the single screw reveals the main filter (C), which is made from a higher density foam, and the low-density foam pre-filter (D). Both are washable with a mild detergent and can be reused. The manufacturer recommends that these filters be oiled to help trap dirt,
but be careful not to overdo it.

 generators_0154 3) The Honda EU2000i has another small panel underneath the carry handle, which allows access to its single spark plug. Remove the boot and the plug like any other engine. The plug should be relatively clean and gapped to .025 inch.

4) Changing the Honda’s oil isn’t difficult, but it can be messy — that’s why Smith Powerhouse offers this handy trick. Bend a piece of common cardboard into a trough and wedge it underneath the filler. Then you can tip the oil out of the crankcase and into a pan without it running into/onto the generator.

5) Cardboard is also employed during refill. Why not a funnel? Because the crankcase holds less than half a quart of oil, and since a funnel makes it difficult to see the level, it’s easy to overfill and make a mess. Pouring the oil in using this method allows you to clearly see when the oil is nearing its recommended level. The EU2000i does not use an oil filter.

6) Smith Powerhouse load tests all the portable units it services, too. Here you can see the EU2000i is putting out 122.2 volts, which is right in spec.

7) If you won’t be able to run the EU2000i for a while, it is easy to drain the fuel from the carburetor by turning this small screw underneath the float bowl counterclockwise. Fuel drains down the tube to the left and out the bottom of the generator. Put fuel stabilizer in the tank, keep the unit indoors, and you should be good for the off-season.

Smith Powerhouse | 562-633 1390 | www.smithpowerhouse.com

Cummins Power Generation | www.power.cummins.com

Honda Power Equipment | www.powerequipment.honda.com/generators



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