Fuel Pump Fittings....

[aturner]

OK, I don't want to make a mistake here.....the engine driven fuel pump on my IO-540 had two simple 90 degree fittings, so I am trading them out for the Van's supplied fittings. The outlet side is fine, this is the KB-090 with an O-ring, washer, and jamb nut. I tightened the nut to 23 ft. lbs. (right?), and everything feels secure and tight.


On the inlet side, the plans call for the KB-000, which apparently does not use a jam nut and washer, just an o-ring.

The problem is that the fitting insets into the pump with little resistance until the nut portion of the fitting contacts the fuel pump. I can tighten it, but this just doesn't feel right. Is the O-ring going to seal properly? Will the fitting not back out? Is this right?

[N427EF]

You got it right!
It seals on my installation and 1000's of others.
There is no need for a jam nut on a straight nipple since orientation does not matter.
You'll have a hose in place and the nipple can't back out provided it is torqued correctly in the first place.

[grayforge]

So no safety wire needed on fuel fittings where they are also connected to hose/tubing via an AN Fitting?

I suppose if the AN fitting let go, you'd have the same problem.

What about safety wiring AN fittings?

Thanks,
Russ

[BobTurner]

There are usually no provisions for safety wiring AN fittings. But be sure you tighten them to the specified torque. Recently there have been a few acidents or near accidents where the builder left an AN fitting hand tight only.

[grayforge]

Whew! I was hoping I wasn't missing something. :-)

[jrs14855]

AN fittings are available drilled for safety wire. In the case of the fuel pump this would be a bulkhead fitting with the jam nut drilled for wire. If you want these try places like Spencer Aircraft in Seattle area or Nor Cal Supply in Oakland CA area.
The straight fitting in the picture is not an AN fitting, rather some type of special fitting for this application. Piper years ago used 90 degree AN bulkhead fittings on both sides of the engine driven pump. By doing this, even if the jam nut should come loose, the fitting will not rotate more than a few degrees. It may leak some fuel but it will not be as bad as is the fitting backs out most of the way.
There have been at least two Rocket accidents caused by loose fittings at the fuel pump, one of these was fatal.