30 micron Fuel filter, small square O-ring.ISC

[Rodger]

I know it’s in here somewhere I just couldn’t find it. Where does the small square O-ring go on the external fuel filter that’s behind the side door of my 04 Endeavor and has that clear separator bowl on the bottom of it?

Edited August 18 by Rodger

[diplomat don]

It goes on the shaft you thread the filter onto. Make sure the old O ring of before putting the new filter on or you will have a leak. Good luck, Don

[Rodger]

34 minutes ago, diplomat don said:

It goes on the shaft you thread the filter onto. Make sure the old O ring of before putting the new filter on or you will have a leak. Good luck, Don

So I assumed this is where it went. But I noticed this time when I put the O-ring on the shaft it doesn’t have a flat surface to seal against. It’s like it catches on the rib of the housing so I can’t see how it does anything. Unless I have a washer missing or something like that?

[cbr046]

A YouTuber's video his (secondary) fuel filter change and it came with that same o-ring.  He showed the shaft with filter removed and no sign of that smaller o-ring.  THEN 3 MONTHS LATER he shoots a second video showing where it was supposed to go. 

It's odd that Cummins Quickserve parts diagram doesn't show the o-ring on the shaft.

- bob

 

 

@Rodger Just re-read your OP . . . . Not sure if the primary filter (the one behind the side door NOT mounted to the engine) uses the same o-ring on the threaded shaft but it's worth a look.  Keep in mind, like "ScannerDan's" video above, the o-ring may have been missing to begin with.

- bob

[Romeo84]

On 8/18/2024 at 10:09 AM, diplomat don said:

It goes on the shaft you thread the filter onto. Make sure the old O ring of before putting the new filter on or you will have a leak. Good luck, Don

🤣 I have double o ringed one before. Was hilarious because you instantly know what you did and just have to laugh at it. Can't stress that point enough. We always tell ourselves this will only take 5 min.... 

[96 EVO]

51 minutes ago, Romeo84 said:

🤣 I have double o ringed one before. Was hilarious because you instantly know what you did and just have to laugh at it. Can't stress that point enough. We always tell ourselves this will only take 5 min.... 

Couldn't tighten it enough to get the perimeter gasket to seal?

The only thing the small O-ring does is keep unfiltered fuel separated from filtered.

It's the outer gasket that keeps air out.

[cbr046]

1 hour ago, 96 EVO said:

The only thing the small O-ring does is keep unfiltered fuel separated from filtered.

Seems the purpose of a filter to me . . .

- b

[Benjamin]

Yes, the square ring is critical in the final filter.  If there's two filters then the first one is there to extend the life of the second, and the little bit that could possibly make it all the way through the spiral of the small clearance of the threads probably isn't going to plug the secondary filter.  I'd expect the threads to plug in short order with any amount of dirt in the fuel.  96Evo is right that the inner seal is not related to air problems, unless you put two on and can't get the outer seal tight.