Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
90 degree fitting on fuel pump ok?
- Thread starter rvator51
- Start date
az_gila
Well Known Member
90 degree fittings are acceptable.
As you know the Lycoming engine pumps use special fittings with a O-ring seal rather than a taper thread. These fitting come in both straight and 90 degree versions.
http://www.aircraftspruce.com/catalog/eppages/gfitting00780.php
http://www.aircraftspruce.com/catalog/eppages/lycomingfitting00782.php
Use the hose you have.
ADDED
An old picture from the EAA Bingelis books -
As you know the Lycoming engine pumps use special fittings with a O-ring seal rather than a taper thread. These fitting come in both straight and 90 degree versions.
http://www.aircraftspruce.com/catalog/eppages/gfitting00780.php
http://www.aircraftspruce.com/catalog/eppages/lycomingfitting00782.php
Use the hose you have.
ADDED
An old picture from the EAA Bingelis books -
Last edited:
Toobuilder
Well Known Member
The general preference is to avoid 90's wherever possible, but it's not an absolute. 90's on the suction side are cumulative, so if you have a bunch already then take a hard look before adding another. OTOH, if this is the only one then you will likely be just fine. Vapor pressure is the issue here, so fuel type and mission of the airplane are considerations too. (High temps, high altitude and auto gas being the worst case)
Michael Burbidge
Well Known Member
Torque
What's the torque value on end that goes into the fuel pump?
Michael-
What's the torque value on end that goes into the fuel pump?
Michael-
They come in 45 deg versions also........
http://www.vansaircraft.com/cgi-bin...0-14-387&browse=engines&product=pump-fittings
deek
Well Known Member
It's a straight thread; no torque. Thread it in until you get the clocking you like and tighten the jamb nut.
Fitting
I have never heard of the fitting coming loose on a Pitts. I do know of two airplanes, I think both Rockets where the fitting came loose and started an inflight fire. One event was fatal to one of the two on board. The 90 degree fitting allows one to reach in and check the integrity any time the top cowl is off. With a straight fitting you will need to put a wrench on it, much more difficult depending on the individual installation.
I tighten the jam nuts pretty tight. It would be a real ordeal to get a torque wrench in there after the engine is on the airplane.
I have never heard of the fitting coming loose on a Pitts. I do know of two airplanes, I think both Rockets where the fitting came loose and started an inflight fire. One event was fatal to one of the two on board. The 90 degree fitting allows one to reach in and check the integrity any time the top cowl is off. With a straight fitting you will need to put a wrench on it, much more difficult depending on the individual installation.
I tighten the jam nuts pretty tight. It would be a real ordeal to get a torque wrench in there after the engine is on the airplane.
deek
Well Known Member
^^^^^^ This; Gud'n'tite. On my first LongEZ I drilled the check nuts and safety wired them. When replacing the failed pump at ~1,200 hours I didn't/couldn't safety wire the nuts. Five planes, 6,000+ hours and never had a an issue with the nuts or the fittings. You need to think through how the motor reacts to torque, and what it does to the fuel lines and fittings over time.
Also a loose intake fitting on the fuel pump
Just this week I pulled my hoses off on my RV4 to change out for some new Teflon lines while I install my flo-meter. I don't know for sure but I'm assuming the lines are original since 1998 and 600 hrs. But to my surprise the straight fitting that goes into my fuel pump was only finger tight. From what I could see it had not started leaking as of yet but probably was not that far off. Mine was a straight fitting and there is no jam nut. Everything else was tight and the O ring looked good.
I bought a new fuel compatible O ring for it and see what happens when I put it back together. If it was sucking a bit of air this might explain the sometimes erratic fuel pressure I was seeing.
Tim
Just this week I pulled my hoses off on my RV4 to change out for some new Teflon lines while I install my flo-meter. I don't know for sure but I'm assuming the lines are original since 1998 and 600 hrs. But to my surprise the straight fitting that goes into my fuel pump was only finger tight. From what I could see it had not started leaking as of yet but probably was not that far off. Mine was a straight fitting and there is no jam nut. Everything else was tight and the O ring looked good.
I bought a new fuel compatible O ring for it and see what happens when I put it back together. If it was sucking a bit of air this might explain the sometimes erratic fuel pressure I was seeing.
Tim
Just to make sure everyone is using the right terminology here...there are "straight" AN fittings, 90 degree AN fittings, straight *threads* on NON-AN fittings.
The Lycoming fuel pumps, as noted above, take "O-ring Boss" straight thread fittings, which can be straight (no jam nut, since it's not necessary, obviously), 45 and 90 degrees (both with jam nuts). All have straight threads on the fuel pump end, AN flare on the other...
I'm sure this is patently obvious to everyone, but there may be some new-to-engine folks here who might be confused with the various use of "straight"
and since fuel systems are critical...Just to make sure everyone is using the right terminology here...there are "straight" AN fittings, 90 degree AN fittings, straight *threads* on NON-AN fittings.
The Lycoming fuel pumps, as noted above, take "O-ring Boss" straight thread fittings, which can be straight (no jam nut, since it's not necessary, obviously), 45 and 90 degrees (both with jam nuts). All have straight threads on the fuel pump end, AN flare on the other...
I'm sure this is patently obvious to everyone, but there may be some new-to-engine folks here who might be confused with the various use of "straight"
Confusing?
I have an O-360 lycoming and I'm assuming it's a Lycoming mechanical fuel pump but being I didn't build the plane and never thought of the pump possibly being different, didn't check (but will) for now I will assume it's a Lycoming.
It was the straight thread butting up onto the "O-ring Boss" that was finger tight. Maybe it does need a jam nut? Maybe it wasn't tightened up when put together? Maybe the o-ring characteristic changed over time relieving pressure on the straight thread butting up onto it?
It doesn't sound like it's a common problem but it has been reported a few times on here so it does raise an eye brow, at least it raised mine as the consequences of this are serious and have been serious in the past to a few people.
Tim
JonJay
Well Known Member
Good on ya for checking and double-checking it. JonJay's link has the right parts for Lycoming pumps. Also, if you're unsure, get a second set of *experienced* eyes on it to make sure.
The straight fitting doesn't need a jam nut, BTW...you just tighten 'er down to the appropriate setting (look in the manual) and then attach the hose on the flared-tube end per standard torque specs.
And note the difference between *straight thread* fittings (like O-ring boss) and NPT fittings...they are NOT interchangeable!
az_gila
Well Known Member
You might want to change the O-ring at the same time. Spruce calls up this part -
The o-ring part number for this would be MS29513-112.
WE use 90*s all the time, but we do plan our fuel systems know that a 90* will be used.
Tom
Tom
Yes, I picked up a black Nitrle O-ring from the Hydraulic shop in town. Will be good to go. Just another check point to pay extra attention to every year. Almost impossible to get too to verify with a wrench but will mark it with a chalk line to assist in the monitoring.
Tim
Tim
