I have leaks at the injection line nuts at the head on a couple cylinders. it is comming from the threads on the bottom. I cant figure out why. they are tight, and the nuts thread in by hand all the way when i take them off so they are square on there. I just replaced all six lines and injection pump last september and they just started leaking now? the fuel delivery tubes cant go bad can they? i am just puzzled at this and frustrated i need this truck every day to haul trailers. any thoughts would be a help. thanks Jon D.

 

I have the same thing going on with #5. The o rings on the fuel delivery tubes can go bad and cause the leaks. I replaced mine and still have a leak though. What I noticed is that there seems to be a wear spot on the tube where fuel could get through. I think my tube is bad but I reduced the leak by at least 50% by turning the tube 180 degrees so that any imperfections didn't line up. ( don't know if that helped..) The other thing i did was to tighten the line nut and then loosen it several times to try to seat the tube and injector line. With what I think I have (a bad tube) it really helped to reduce the leak.
Hope that helps

 

About 50% of the leaks I see are caused from Over Torque. These lines are only supposed to be torqued to 28Ftlbs. The rest are scuffed or damaged connector tubes and bad O-rings. Make sure you use the cummins o-ring or you'll be changing them often. Also, In the shop we pull the lines all the way off and clean the flares very gently with emory cloth!

 

thanks for the help i will try some new o rings. dose over touqing damage the fuel tubes?

 

Normally just the lines! If the line was installed incorectly against the connector tube it will cause damage. Most times you can get them to reseal though!

 

Wow never heard of using emery cloth before, I would think just blow off with air and wipe ends with clean shop towel. Emery would cause problem if small particles got into the injector even if you blow it off with compressed air.

 

We use it wet and in some cases we'll just do a light wet sand on them. The tubes and lines are well soaked wiped with lintless rags blown off a few times and their good to go. Your NOT removing any material off of the line, Only the light surface buildup seen.
It's more about corrosion and build up. Never had a problem yet. I wouldnt recomend it on a CR truck.