7.3 IDI Return Cap #2 & #8 won't seal

[JHolt55]

I've been battling this issue for the past 3 weeks on my truck, its always a major pain every time I do the return caps on this thing. But the caps for #2 & #8 won't seal up for more than a day no matter what I do. I am using number 111 Viton "o" rings, and have tried two different brands of caps both had no burs or damage. I have tried using engine oil when installing the "o" rings and the caps, as well as my old method of white lithium grease. I tried replacing the individual caps that are leaking as well as the entire bank of caps, and have cut the hoses so there is not bending between them. After one day of driving the caps start leaking. Here is my return line routing that worked best in the past, I have the fuel filter return removed. The IP return does not enter the cap system since I believe it was causing more leaks with the added volume of fluid to move. I believe the issue is vibrations from the line between cylinders 1&2 that causes #2 too start leaking, and I would like to remove this cross over but I can't find a 1-way dead end late style cap. Would the 1-way early style barb cap work with the newer size hose? The leak for #8 I believe is caused by the short line between its cap and the factor 3 way block bolted to the intake. I can't figure out a better way than it already is, I have the block rotated so it shouldn't be putting pressure on the cap.

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Anyone have a better routing method?

 

[Old Goat]

the line from #1 - #2 could be eliminated.
Cut a short piece of hose and insert a bolt with spring clamp.
I doubt there would be vibration between 1 & 2 to cause a leak.

If you are using rubber hose from an auto supply, it will retain
it`s curve when cutting the short pieces. Place one with the
curvature one way, the next the other way etc... this will keep it
all in line w/o any stress on the Nip ple connections.
Mine is this way. Bought Gates rubber hose from O`Really`s.

Now if you have one leaky cap/O Ring, removing just that one
for the fix, you will cause the next to leak etc...
Been there.
I just remove the whole side, replace the O Rings or what ever,
and replace the whole side as an assembly.
Be sure to grease the O Rings when installing on the Injectors. Place
first one on top groove, then roll the 2nd one over it to eliminate
any possible nicks in the rubber, if it were to happen.
Be sure to grease the inside the caps also. Any grease will work.
Well has for me.

I do not have the return from the filter to the Injector Cap. Been
that way a long time. There was a Ford TSB several years ago to
remove it. Was causing problems with some engines.

Early style caps and later style use different size return hose.

Keep the cap`s you replaced, they may not be bad. Might need one,
one day.
I have a container full I got from PNP at different times, some brand
new. Even kept the Spring Clamps. I have seen the regular screw
clamps used, forget it. the Springs clamps keep constant pressure on
the hose.

Goat

 

[Kdo58]

These are the best I've used
The YouTube video

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[Old Goat]

Diesel Tec Ron, has a lot of video`s on the Power Stroke.
I think this is the only one on the IDI engine.
He loved helping people.
He was killed one morning in his VW going to work.
The family is keeping his video`s up to help others.

This is a great video.


Goat

 

[JHolt55]

Thanks for all the information guys, I think I will try out the washer on top of the cap since that seems to be some of the problem. Interestingly the leak has mostly self healed, and only leaks a little bit during the first 20 mins of use everyday after that it "heals" itself and stops. I haven't noticed any air intrusion but I do run a Dura-Lift pump so that could be covering it up. I guess my next step is taking off the driver side cap line and resealing, deleting the front cross over and adding in copper washers on top.

 

[Sparks-IDI]

I was having the same issues as you with the leaky caps. I then tried using a square section viton oring. That provided more rubber surface contact and sealed my leaky caps right up. Just provide a bit of grease on the injector as you carefully twist the cap on. I bought them from McMaster Carr Dash no. 111, part no. 1170N53. About $15 for a bag of 10.

Give them a try if your still fighting this problem. Worked for me.

 

[ROCK HARVEY]

The only thing I would add is to make sure your steel injector lines aren’t bent out of shape. When they’re unscrewed from the injectors they should naturally want to sit right above them, not an inch or two to the side. That’s the only time I’ve had trouble getting o-rings to seal.

 

[WrenchWhore]

First thing i'll ask is are these the OE return line caps or aftermarket? If you put a micrometer on the inside of the cap where the O-rings seal and it's like (.010") different it's probably an oversized return line cap. I battled this when I couldn't get my aftermarket return lines to seal. The aftermarket straights were fine but the turns were all oversized and leaking. I ended up going back to the original caps because they were tighter fitting. Zero leaks and has been for over a year. Did a new motor recently with the same caps and still zero leaks even with the cheap O-rings. Lots of aftermarket junk out there. Use grease when installing. Diesel IMO isn't thick enough. The best chance to not damage the O-rings is grease. Next make sure you blow compressed air over the leaky ones and make sure it's leaking from the actual return line cap and not from the hard injector line. Hard lines can be over torqued, crack, and LOOK like it's a return line cap/o-ring. Good luck.

 

[danda]

also, its very important that you not look at them funny. Or at all, really. they are very sensitive.