What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Lycoming/Tempest Fuel pump fittings

kjelle69

Active Member
I am thinking of changing my Aluminium fittings to steel.
I have a straight fitting and thats no issue but I also need a AN804-6 fitting.

Looking at the recommended pump fittings when you have an elbow fitting attached to the pump it seems that it's a washer combined with an O-ring that is needed. That makes sense but is the washer of some special type? In the attached image it also seems that there's actually two washers or an O-ring combined with a second washer. I dotn really get this?
 

Attachments

  • fittings.JPG
    fittings.JPG
    87.2 KB · Views: 103
The washer/nut combination is what makes it possible to orient the fitting in the desired orientation by compressing the o ring into the lands of the fitting/pump.
 
Yes I understand this but the combination in the red circle makes me wonder if there's only a washer and an O-Ring. It seems in the second image that there is another washer and that some compression has occured?

This is the solution installed right now and I am not really satisfied with this.
The blue AN804-6D fitting is on the inlet side. The builder have an o-ring and what seems like a composite washer. The nut has a groove in it. I guess the purpose of this fitting is to go through a firewall ond not to be attached to the pump. It has worked for several hundreds of hours tough...

The straight fitting is on the outlet side, also aluminium. The sealing there is the same as in the Vans image.

The washer/nut combination is what makes it possible to orient the fitting in the desired orientation by compressing the o ring into the lands of the fitting/pump.
 

Attachments

  • 20220402_111558.jpg
    20220402_111558.jpg
    240.5 KB · Views: 72
Yes I understand this but the combination in the red circle makes me wonder if there's only a washer and an O-Ring. It seems in the second image that there is another washer and that some compression has occured?.

The fitting includes a nut, washer and o-ring. You install fitting to orientation then tighten nut/washer/o-ring for sealing.

07-00783.jpg
 
The washer/o'ring fitting, or o'ring boss fitting, is actually an industrial hydraulic fitting that Lycoming, Tempest and others use for this application. The washer applies even pressure to the oring when the nut is tightened so the oring seals in the groove of the threaded port.

Yes---you can use a AN union, or a bulkhead fitting with a washer and the proper o'ring. There are 2 versions of the 'industrial' fitting, a brazed version, and a forged version. The brazed looks like a block--like the op's pic with the male JIC side (Yes, JIC, not AN) brazed into the block. The forged version is a 1 piece forged unit that is machined, and it more closely resembles a real AN fitting. Yes, it also has JIC threads, class 2 and not class 3 AN threads, but there is no issues there at all. Certified planes have had these for decades with no problems, as long as you tighten the lock nut after indexing.

Tom
 

Attachments

  • MS bulkhead fitting.jpg
    MS bulkhead fitting.jpg
    395.1 KB · Views: 71
  • 6801-0606NWO.jpg
    6801-0606NWO.jpg
    133.9 KB · Views: 57
Back
Top