Injection pump check valve installation

[wwheeler]

I have some quick questions regarding installation.

I am going to install new check valve seals. What torque do I use for the pipe union fittings? I have seen 18 ft lbs. on this site. I looked in the BBB torque chart and for a 280, it shows to be 3.0 KPM (21.7 ft. lbs.). I have also read in Hayne's that you should 1st torque to 29 ft. lbs, back off and then tighten to 25 ft. lbs. Strangely, the BBB (07-13/2) has the proceedure listed and says the same as Hayne's. Why is the BBB proceedure torque spec different from the BBB Torque chart spec? Is it because it is a new seal versus installing an old seal? Which is the best torque?

According to the BBB, the injection pipe couplings should be 2.5 KPM (18 ft. lbs.). The pipe couplings of course should be less torque than the check valve union fittings.

And finally, when I unscrewed the check valve unions, some didn't unscrew easily by hand. When looking at them, it appears that they had some form of thread sealer on the threads. Is this necessary? I would think the seals below would take care of that.

Thanks for the help!

[wwheeler]

One last question:

What is the thread size (12mm?) and the thread pitch of the ball check valves?

Thanks!

[mbzse]

One last question: What is the thread size (12mm?) and the thread pitch of the ball check valves?

if it is the part depicted in this forum posting http://www.sl113.org/forums/index.php?topic=7684.0

the thread on the top part of this pressure valve is M12 x 1 [metric fine pitch]
/Hans in Sweden

.

[wwheeler]

Thanks for the info and link Hans! I looked for a thread but just didn't use the right keywords I guess.

Looking at the valve, I was thinking it was either 12mm x 1.25 or 1.0. So 1.0 it is. I will make a tool for it tomorrow.

While at the hardware store, I was amazed to find (4) different thread pitches for 12mm (1.75, 1.5, 1.25 and 1.0). I always thought metric sizes just had two common pitches. Learn something new......

Any thoughts on the torque values?   

[wwheeler]

Check valve removal tool made and successful!

Pretty easy to make. I used a 12mm x 1.0 nut and hex bolt from the hardeware store. I welded them together but you could also use steel epoxy to secure the two. I then machined the hex nut down to 18mm which just fit in the threaded hole. Grinding the hex points off the nut will also work if you don't have a lathe. Screw the tool on the outside threads of the valve down until the bolt head contacts the valve. Next (a bit crude but effective and cheap), clamp a vise grip plier under the bolt hex head and use a small hammer to tap the valve out.

That's it.

[ja17]

Nice Tool and good idea Wallace.

I use the fittings on the metal air suspension lines of old MB sedans to make the tool. They are the correct thread diameter and pitch.