Onan fuel filter change

[Max Hubrich]

Thought some folks might like to know how I changed my gasoline Onan generator fuel filter.

I was running my generator while the RV park I'm in, was undergoing some electrical upgrades- commerical power was off for about 6 hours. My generator started coughing and sputtering after 30 minutes. Since the fuel filter has never been replaced (118 hrs), in 10 years, I figured that would be the prudent thing to do.

Here are the pics and some things to be aware of if you need to do this to your rig.


Here is my unit-




The fuel filter is located underneath the generator, to the rear of the unit. My generator is mounted in the rear of my rig on the passenger side. My old filter is attached to the rubber supply hose shown here. It screws into the low pressure fuel pump.







I have the Kobalt knife in the pictures only to show the size of the old fuel filter




Use your small vise grip pliers to pinch off the rubber supply line before you do any loosing of the fuel lines!




If you don't, you'll deplete about 60 gallons of gasoline from your gas tank in a hurry- and you'll come out looking like this .
This also answers the age old question for the novice like me, "Is the generator gravity fed with fuel?"- Yes- it is both gravity fed, and it also uses a small, low pressure, 12v electric fuel pump.




Here is the new filter ($12 bucks)-




Use this, or a similar product, that's approved for gasoline usage, and put a small amount on the "screw end" threads that goes into the fuel pump. I didn't- and I had to go out and find some to finish the job. I could not stop the fuel seepage without it-




Job complete and if you look close you can see the small white bead of sealant on the "screw in" fitting end.



Hope this helps you in your future fuel filter install endeavors-

Oh, my generator ran fine for an hour test run after the filter change-


Good luck,

[Midniteoyl]

Good write-up.. thanks!

[CLIFFTALL]

Originally Posted by Midniteoyl

Good write-up.. thanks!

Ditto. Thanks. I carry a spare filter and thought I would ask how to change it when the time came. Now I don't have to.

[Lincolnboy2]

Wow! I'm impressed!

Is it my imagination or is the new filter shorter than the old one?

Mine is a 5500 about 10 years old and the first owners only put about 60 hours on it in 9 years and it probably should be replaced as well. I don't have any problems, the genny purrs along great, but I know it should be done due to the age, anyway.

This is very helpful and I appreciate your sharing the pictures and the procedures!

[Max Hubrich]

Lincolnboy2-

Both are about the same length. The diameter is larger on the new filter.

[Lincolnboy2]

Originally Posted by Max Hubrich

Lincolnboy2-

Both are about the same length. The diameter is larger on the new filter.

Very good....thanks again!

[Dalsn1]

On my Onan the fuel filter was mounted directly to the carb. These were prone to leaking and Onan has released a kit that relocated the fuel filter from the carb to the fuel pump location shown in the post above. I also replaced the short rubber fuel hose.

Steve

[JFGOBUCS]

Great and Informative info...Thanks!

[Max Hubrich]

Steve

You bring up a great point. I think my generator has two filters. I also have what looks like a small filter at the carb.

Here is a picture of the setup-



I just couldn't believe Onan would put two filters on this small engine.

Look at item 18 and the note.

I don't have time to get into this today- I'm in the middle of a TV upgrade install (a 32" Sony LCD HD) in my neighbors '03 Dutch Star DP.

I'll follow up soon--next week.

[Midniteoyl]

Coarse pump inlet filter... fine carb filter

[Max Hubrich]

Okay boys and girls, here is the update ya'll are anxiously waiting for-

It's been a busy week, or so, for me. Installed a 32" Sony HD LCD into a Dutch Star DP, Mardi Gras, bad weather, and today in the ER for pneumonia. I feel good, but my cold got down into my chest (lungs). I'm home now, doing good and feeling good.

The Air Filter housing. The old gas filter is the small gold color looking item right below the silver, vertical mounted clip.




We're now zeroing in on the little devil-




Now remove the 4 bolts (only 3 shown- the 4th is on the right side of the carb butterfly valve- the brass colored "thingy"). The filter cover will come out after tugging a bit on it to clear it off the lower large rubber gromet for the air intake. Note: the Carb is now also loose on long studs- carefully remove the two small spacers (and place in a secure place) and the gasket on the outer ends of the studs.




Pulling the carb outwards slightly will give you ample room to remove the old gas filter. You can forget reusing the OEM clamp. Just cut the hose off and add a new clamp. There is ample gas hose there.
Oh, you don't need to pinch this supply hose off like the one feeding the lower filter.



Sorry the picture is fuzzy- getting old- It was windy, cold, and I was getting sick .




The new replacement part




The new part with both old filters. The really grimmy one was the one down below the unit and subject to more road debris than the carb one. Note: that Onan put a sealing material on the new replacement part- I also added a small bead of my sealant, as I did on the new lower filter.





Walla-- And while your looking at the altitude adjustment on the carb, if you have an erratic running generator adjust this little beauty to your average operating altitude for your use. I operate near sea level in my travels. When I bought this rig my generator was pulsating in RPM's and this cured that. I think it was factory preset for an average altitude, higher than my operating zone.
For example, If your in the Denver or Albuquerque areas your altitude is 5- 6000 feet.







Now folks this is the time to replace the two spark plugs as access is now available to the left cylinder. For the above stated reasons, plus a few more, I didn't do that to my unit. Next oil change I'll attack that project. Also replace the air filter at this time- I had done mine recently.

I find Onan parts on line are very reasonable and processing is outstanding- .

I will cut those two old gas filters open on my lathe when I get home in April- I want to see what's inside them since I had a significant power loss event recently- Stand by for that exciting bit of forthcoming news-

Good luck on your project-

[CLIFFTALL]

Thanks Max. Great explanation and photos.

[Max Hubrich]

Okay--

I got to the home place in NC, and to my shop. I cut the two old gas filters apart on my lathe and here is what I found- Absolutely nothing!!


# 1- is the first one in line from the rigs gas line.

# 2- is the filter mounted on the carb.

They both were clean as a whistle-




I have no idea why I had the generator stumble awhile back.
It had about 116 hrs on it when it did it. I change the oil and clean the air filter yearly.

It's been running fine since I replaced the filter as noted in my previousl threads- Go figure-

[CLIFFTALL]

Originally Posted by Max Hubrich

Okay--

I got to the home place in NC, and to my shop. I cut the two old gas filters apart on my lathe and here is what I found- Absolutely nothing!!

# 1- is the first one in line from the rigs gas line.

# 2- is the filter mounted on the carb.

They both were clean as a whistle-

I have no idea why I had the generator stumble awhile back.
It had about 116 hrs on it when it did it. I change the oil and clean the air filter yearly.

It's been running fine since I replaced the filter as noted in my previousl threads- Go figure-

Thanks for the update. I'm confused as well.