Torque Value for Injector Jumper Tube Nuts with the O-rings seals

[ake1994]

My 87 MC9 with the 6V92 DDEC was making oil. I found the problem with several of the Jumper tubes leaking fuel into the crankcase. Luke at US coach has fixed me up with the parts and I am ready to re-assemble. But I need to confirm what the torque value is for the Jumper tube nuts. MY engine has the newer style of jumper tubes with the O-ring seals, not the tubes with the flair and flair nuts. I have a 2003 Detroit manual and in section 2.3.4 it describes the installation of an electronic Injector and indicates 143 lb-in of torque on the nuts. But the figure shown is of the flair style nuts. This is the same value shown in a table in the 1979 Manual as the torque value for the flair nuts on an electronic injector. This makes me think that the 2003 manual is also referring to the tubes with the flair nuts. A I am having trouble finding conclusive information on the correct torque value for the nuts on the tubes with the O-ring seals.

Thanks folks,

Breck

[luvrbus]

No answers yet ,it is 13 to 17 ft  lbs for the o-ring type  

[eagle19952]

No answers yet ,it is 13 to 17 ft  lbs for the o-ring type  

148 in/lb = 12.3 ft lb.

close enuff for the girls i go with

[Geoff]

Yup, hand tight, light pressure.

--Geoff

[Iceni John]

My DDEC II troubleshooting manual says 12 to 15 ft/lbs, so it looks like we're all in the same ballpark.   When I replaced all 24 jumper tubes' O-rings a few years ago when I overhauled my Jakes, I realized the O-rings cannot get crushed regardless how tight the nuts are.   I was more concerned about over-stressing or bending the thin part of the Snap-On split socket tool for the nuts, so I used a 1/4" t-handle driver in a 3/8" adapter.

John

[ake1994]

Thanks guys,

I finished the job last night. Torqued all 24 nuts to 143 In-lbs. I too was more concerned with over tightening as the sealing is dependent on the o-ring. The old o-rings seemed to be harder or stiffer than the new ones. I know they have been in there for a least 9 years. Ran it for a good while with the Covers off and couldn't see anything obvious leaking like it was. Time will tell as I watch the dip stick.

Thanks again! My manuals were not very clear, but I felt good going with the consensus.

Breck

[luvrbus]

If you ever need a torque value and the manual is unclear the PC Industries will have all the last updated torque values on their web site for the engines,15 lbs is my standard

[ake1994]

luvrbus,

Thanks for the Tip!

[bevans6]

when my engine with those jumper tubes was making oil, I changed a ton of stuff, including those o-rings.  At the end of the day the last thing I changed, and hence the thing I think fixed it and was the problem, was the stand-offs - the 2" or so long pieces that stand up off the head and those jumper tubes attach to.  They have a hardened washer under them, need to be torqued to around 45 ft lbs from long ago memory, and mine were done up "tight".  I took them all off, cleaned them up and checked for burrs, and put them back in with a torque wrench, and the leak went away...

Brian

[Oonrahnjay]

... I took them all off, cleaned them up and checked for burrs, and put them back in with a torque wrench, and the leak went away...

Brian

      Did you have to replace the washers, Brian, or were they OK with just cleaning?

[bevans6]

As I remember they are very thin and hardened steel washers, and I did not replace them.  I might have expected to if they had been crush washers, but they were not crush washers.

[Geoff]

The proper way to test for a fuel leak to the oil is to pressurize the fuel system​ to 60 psi and look at all fuel parts for leaks. I have found fuel stands, injector fittings, and of course, jumper lines.  On another note, I found a bag of the right size "O" rings on eBay that are fuel resistant, something like $5 for 100 O rings.

--Geoff

[B_K]

The proper way to test for a fuel leak to the oil is to pressurize the fuel system​ to 60 psi and look at all fuel parts for leaks. I have found fuel stands, injector fittings, and of course, jumper lines.  On another note, I found a bag of the right size "O" rings on eBay that are fuel resistant, something like $5 for 100 O rings.

--Geoff

We had an 8V92 DDEC that was making oil once we checked everything and could not find the leak anywhere! We tried pressurizing it and even put a dye in it that was supposed to show up with a UV light still couldn't find it.
I was working late at night getting another bus fixed for a morning trip and decided what the heck let's see what I can find in the dark!
So I filled the dye injector, hooked up air regulator, and went inside the bus with the UV light and hokey smokes looked like lightening bolts on 5 out of 8 injectors!
Had all 8 injectors checked out and 6 out of 8 were cracked!
Put new injectors in it and it ran like a top!
  BK 

[ake1994]

Thanks guys,

Lots of good insight as to where to look next if my problem is not cured. Only been about 50 miles and so far the dipstick looks good. My leak was fairly small, so if it's not fixed it will probably take time to show up. I think I was at a couple thousand miles when I noticed the oil was up about a gallon. Want to take a couple of 200-300 mile trips late in June. So I'm hoping I can find out then how it's doing before I go too Far?

Will update everyone after the first trip.

Thanks,

Breck

[B_K]

The 8V92 was making oil so bad I was changing the oil in the hotel parking lot every night until I could get the bus home and get it in our shop!
  BK