Onan 12.5K Generator - Fuel Filter Replacement

[LWBAZ]

The Onan 12.5K generator in our 2018 Cornerstone just hit 1,000 hours. I've completed an oil change (including installation of a Femco drain valve to make that particular job easier in the future), oil filter replacement, and air filter replacement.

Next up on my generator to-do list is replacement of the fuel filter. I have experience replacing fuel filters on the virtually identical Onan 10K generator that was in our 2010 Tiffin Allegro Bus, so I'm familiar with the basic procedure. But Entegra's sliding tray is different than the one Tiffin uses, with its air cylinder impeding access a bit.

Any tips/advice regarding the best way to accomplish this fun little job will be appreciated!

[Hayman]

Hi Larry , As I'm sure you already know removing the side panel gives you access to view the fuel filter and the filter housing is bolted in place to a bracket.
Unbolt the filter and pull/work ( fuel lines are flexible ) the filter up and out of the generator frame where you'll be able to undo the lines from the filter. Reverse process for replacing the new filter. Easier then it looks just be prepared to skin a knuckle or two !

[BobG88]

Larry,

Here are a couple of links that may help:

https://www.irv2.com/forums/f278/ona...ml#post4515632

https://www.irv2.com/forums/f278/cha...-443585-2.html

BG

[Gary.Jones]

Yep, don't remove the fuel filter..... rather, remove the fuel filter bracket holding it to the generator engine.

Gary

[buddy110]

Originally Posted by LWBAZ

The Onan 12.5K generator in our 2018 Cornerstone just hit 1,000 hours. I've completed an oil change (including installation of a Femco drain valve to make that particular job easier in the future), oil filter replacement, and air filter replacement.

Next up on my generator to-do list is replacement of the fuel filter. I have experience replacing fuel filters on the virtually identical Onan 10K generator that was in our 2010 Tiffin Allegro Bus, so I'm familiar with the basic procedure. But Entegra's sliding tray is different than the one Tiffin uses, with its air cylinder impeding access a bit.

Any tips/advice regarding the best way to accomplish this fun little job will be appreciated!

Unbolt the piston on the right side and pull it out of the way. IIRC that's all that was needed.

[LWBAZ]

Thanks to all of you for the responses and recommendations.

With all this great advice, I do believe I'm armed & dangerous!

[Hayman]

Originally Posted by LWBAZ

Thanks to all of you for the responses and recommendations.

With all this great advice, I do believe I'm armed & dangerous!

DANGEROUS at least ! 😄

[LWBAZ]

Originally Posted by Hayman

DANGEROUS at least ! 😄

All day, every day!

[Jolar01]

Not that you didn’t get the fuel filter changed earlier, but based on guidelines it should be changed at 450 hours waiting till 1,000 is living on the dangerous side. Wishing you well, I always struggle getting the damn filter out, it’s always a hassle.

[LWBAZ]

Actually the maintenance interval for the fuel filter is 500 hours rather than 450, according to the Cummins-Onan Operators Manual applicable to my 12.5K generator (see images below from that manual).

Either way, I haven’t changed it so far and didn’t plan to until the generator hit 1,000 hours. If it was an easier job I might do it sooner, but this is the fourth RV diesel generator we’ve owned (one Generac and three Onans) and I’ve never changed fuel filters earlier than 1,000 hours.

I’m very religious about oil, oil filter and air filter changes, but not that worried about fuel filters. I say that because the generator draws its fuel from the same tank as the main engine and I make it a practice to purchase fuel only at the major truck stops (Love’s, Flying J, Pilot, Petro & TA), which minimizes the chances of getting contaminated fuel.

I’ve considered doing what a friend of mine did, which was to install a spin-on fuel filter in the fuel line leading to the generator, mounted in a location that makes it easy to replace. The idea being that if you change that filter on a regular basis you could go a long time before needing to replace the hard-to-access fuel filter inside the generator.

My friend installed a small Parker Racor filter like the one in the photo below, but a Gar-Ber filter like the ones on most Aqua-Hot installations would work equally well.

[Jolar01]

I agree that the 10K & 12K Onan generator fuel filter change interval is 500 hours as you indicated, I misread the chart and quoted information from a different generator. As to extending the service interval to 1,000 hours I would be careful and always carry a spare filter and not be mad or upset that while boondocking the generator stops. Of course it will be in the middle of the night, miles from anywhere.

I have had the filter go bad once, the codes were straight forward if I remember correctly this was about 600 hours or so. I didn’t have a filter at the time of the second oil change so ordered one then forgot to install it.

Your idea of installing a spin off filter is excellent, finding a place that is secure and accessible may be a challenge, also Cummins warranty issues may require some attention.

Larry

[rpasetto]

I like @LWBAZ idea of a spin-on filter. It is a PITA to change now, especially on the older 12.5k models which have a metal fuel line from lift pump to the filter so filter cannot be moved up to change it.

I was planning replace the metal fuel line with a hose, like I've seen on some of the newer Onan models. But while I'm at it, why not put a small spin-on filter in there... If someone has done that I'd sure like to know.

[LWBAZ]

Originally Posted by rpasetto

I like @LWBAZ idea of a spin-on filter. It is a PITA to change now, especially on the older 12.5k models which have a metal fuel line from lift pump to the filter so filter cannot be moved up to change it.

I was planning replace the metal fuel line with a hose, like I've seen on some of the newer Onan models. But while I'm at it, why not put a small spin-on filter in there... If someone has done that I'd sure like to know.

Rick, I doubt you'd have room for a spin-on filter and associated top plate inside the generator. My friend mounted his spin-on filter outside the generator itself, about halfway between the coach fuel tank and the generator.

He left the original filter inside the generator, but another approach would be to remove that filter and connect its input and output lines together with flexible fuel hose. The idea being to end up with only one fuel filter that is quick & easy to change.