Dave is pointing out the correct feature of concern on the Racor filter arrangement, the vertical plastic tube to the left of the Cat filter. I had done considerable research with Racor going back to getting the original Wynn designer (see below) I had replaced the tube and Orings thinking I had an air leak and it did not resolve the void in the plastic tube...when the purge pump fails you will have to change this unit out and Dave has pointed us to a good alternative.
The Orings age and the plastic ages and can crack. If you see yellowing of the plastic, cracks in the plastic, any fuel seepage this unit needs to be updated. It would be wise given those weaknesses to have a change interval of 10 years in mind for the plastic tube unless a visual inspection shows concern sooner.
From prior posts...
While I know in the world of diesel fuel filter bowls and filtration that they are normally full with no air passing through them and that air is the devil. If you are talking about the 12963 unit with the clear plastic filter and vertical metal screen I can assure you that unit will not be full by design. I had the same questions about that unit and called Racor Tech support, they actually got hold of the Wynn designer and we had a 3 way discussion regarding this unit, how it was designed, and how it functions. If it was a closed plastic housing on the bottom of a filter then it would separate water (water settling at the bottom) and any air would flow out the top fuel exit and the housing would stay full of fuel by design with no air leaks.
The vertical tube with the screen is a large debris filter that was built in in the inlet stream just to supply minimal filtering so the electric purge pump did not get damaged. The fluid by flow characteristics is actually pulled apart creating a void and this is not caused by air coming in. I changed the Orings and plastic housing in mine thinking I had a leak that allowed air in and the results were the same. A new filter with less restriction actually changes the level of fuel in this housing. I think the suction pulling the fuel up out of the housing exceeds the ability of the flow coming in. If you watch closely you will see that there is actually no air within the incoming fuel stream. This is a strange design that goes against all diesel fuel supply logic and I have a hard time visualizing how this works also, but it does...strange but true.
From another post:
The reason for my post was to let folks on the forum know that for the Parker 12963, having the vertical plastic housing with the metal screen inside not be full while running the engine, is unique as far as visible diesel sediment bowls (which this is not) is concerned and that they should not to be alarmed by this, it is due to the design. The only time it is full is when you shut down. Unit in this link.
https://www.parker.com/portal/site/PARKER/menuitem.bb22d5a82bbb5b147cf26710237ad1ca/?vgnextoid=a2d9b5bbec622110VgnVCM10000032a71dacRCRD&vgnextfmt=default&vgnextcatid=2913342&vgnextcat=RK12963%20INTEGRATED%20RETROFIT%20KIT&vgnextdiv=687630&vgnextpartno=RK%2012963&Wtky=These units are not without their flaws. The electric pumps are prone to fail in time, so if you cannot purge this unit it needs to be replaced. The plastic housing for the screen tends to crack with age so that should be changed at some interval, and the Orings on the plastic housing can fail. Any seepage of fuel on these units should get sourced and corrected. My diesel mechanic showed me the fuel void in the plastic housing and told me I needed a new filter unit, he said he had changed out several already for this same problem. I would guess that many of these units have been mistakenly changed over the years thinking they are an air leak source. He was not alone in assuming these units are bad.
If anyone has a 12963 unit that has a full screen housing that remains full while idling let us know. I believe the fuel pull is out the bottom and there is a column of air free fuel leaving the plastic housing as long as there are no cracks or leaking Orings. It is just the nature of the beast by design...
This is a posting about the O-Rings...A little follow up....I changed all of my fuel filters today and installed the 300200 new filter screen in the plastic housing. There are a total of 4 Orings involved if you want to renew what was installed to seal the plastic housing ends. The two that come with the new housing are .609 ID by .139CS and are a Part Number 208 (AS568B Aero Space Standard Sizing). These are the larger CS (cross section) O-rings and reside in a recess at the end of the metal castings that face the plastic screen filter housing. About 1/2 inch inside the housing at the top and bottom is a recess in the casting where the .612ID by .103CS Part Number 114 resides.
The only problem I had was with a full tank of fuel I was getting siphoning and the fuel flow would not stop. In the end I had to tightening the old housing back up and move the RV to park nose down in order to stop the fuel flow. My driveway has about a 16 inch rise from front to rear wheels parked and that did the trick. I called Gerald about my fuel flow issue and he had put new O rings in his when he had less than a 1/4 tank of fuel and did not have the problem. (Gerald thanks for the insight as always) I still think carrying a set of these 4 Orings is a good idea just in case you begin to see fuel seepage from the housing...Hope this helps.
Later Ed
