Wednesday, May 1, 2013

Nasty Fuel And Air - Changing/Cleaning Your Generator's Fuel & Air Filters

Air Filter Cover
    My generator was starting to do strange things at idle; surging (going up and down RPM-wise) without a load on it. Turn on something (like the A/C) and it worked great. After some research, I decided that I likely had some gunk (that's the scientific word!) in my carburetor and also the fuel and air  filters hadn't been replaced in a long while. I looked up my generator (Generac NP-52G) and ordered new filters. Now all that was left was to install them!  As usual, sounds like an easy thing to do.

First, wipe down the outer surfaces of the generator, paying close attention to the air cleaner housing.
Then, remove the housing covering the air filter elements. On the Generac, (most RV models) it's a simple hand turned screw at the top. Once open you can see the paper element. Mine wasn't too bad, but for the price; $10.90 why not replace it at the same time. I saved the old one "just in case."  I tend to save parts that are not completely worn out, since there is a good chance you could use them in a pinch. The tough part is knowing which ones to take with you and which ones to leave at home!

Once removed I found I actually had TWO filters. The other one is just a piece of foam with a metal mesh on it. Looks like it's for catching any fuel spit out by the carburetor. I didn't have a new one, but I can order one for $1.90 and probably will.  These fit together stacked up. It is a bit of a pain to keep them aligned. Look for tabs on the side of the foam filter and slots on the housing. You may have to war/bend it a bit to get them in, but it will help them seal properly when replaced.

Removing that will expose the cover for the air intake and carburetor. I wiped it down with a soft cloth to remove any dirt and/or grime from underneath. It was pretty clean.

If you ever need to get to the carburetor or linkages to lubricate and or inspect them, the two bolts on the metal plate can be removed for access. Remember there is also a hose that is press fit into the housing on the back! We'll cover cleaning the carburetor in another, more in depth, article. Put on the the new filters and replace the housing. Done.

Old And New Fuel Filter
Next is the fuel filter. My installation puts the fuel line and filter on the right side of the generator compartment, easily accessible from the opening.
This is NOT always the case. A friend of mine had to disassemble the top of his generator to have enough working room to replace the filter! YMMV!!
Usually there are two screw-type hose clamps holding the fuel filter on; one on either side. Loosen each one. Be prepared to catch any fuel remaining in the lines! A simple rag underneath works wonders. You could also clamp off the intake (fuel line side) and run the generator dry. Remove the two hoses from the filter

See The OUT Marking?
MAKE SURE YOU PUT THE FILTER IN THE CORRECT DIRECTION!!! Most filters are marked with an arrow, or like mine with a clearly labeled, OUT. This tells me that fuel will be coming OUT of that end and it should face the generator.

Leave the hose clamps on the hoses.

Make sure the fuel line is in good condition and nothing is obstructing the ends. Then push on both ends of the new filter. Again, make sure the orientation is correct! Once done, tighten the hose clamps to secure it.

That's it. All installed. Start up your generator (it may take a few extra cranks to get fuel back into the lines.) and let it run for a bit. If it's running fine, all is good to go. Make sure you check for any leaks (both fuel and air) before closing everything back up.

Not really all that bad of a basic maintenance item. I also check the oil level and general condition when working in the generator compartment. Look at the wiring and make sure everything is secure and there are no frays or breaks. Could save you a massive headache later in the season.

So, after doing all of this, my generator is still surging at idle. Yup. Murphy was an optimist. Next week I will be removing the carburetor and cleaning it fully. Hopefully it's just a bad old gas/varnish problem. Stay tuned.

Be Seeing You...Down The Road,

Rich "The Wanderman"


  1. John ConnaughtonMay 4, 2013 at 9:45 AM

    Hi Wanderman, if its not too late, before you remove and clean the carb, I recommend trying to clean it in place with SEAFOAM. I was having similar probs last summer and I did this and it cleared it up. After I had cleaned the Air Filter and ordered a replacement Fuel Filter, which I did not wind up using, but have it in my spare parts box, for when I need it.

  2. John,
    Yup...I use Sea Foam all the time. This time, it didn't fully clean the idle jet. Removing the carb (not really that time consuming nor difficult) is the easiest fix.


    Rich "The Wanderman"


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