I'm visiting a friend and when we were using his truck (05 Ram ~ stock) to take large pile of trash to the dump, when his #4 fuel line started to leak due to a crack in the line next to the fitting. 

When we went to the dealer for a replacement, they had a few on the shelf and told us this line has had problems of cracking. Per the dealership parts guy, the line is so short, it can't take the vibration over time. This Cummins replacement is different because it is now designed to give a slight flex for the constant vibration.

Installed and it was working perfect. But my friend said this happen before. At 130k the first time and 180k this time. Geno's has a replacement that looks the same.

Does anyone know of this weakness and if these replacements actually work better than the stock fitting ?

 

Is this a common issue and I haven't found any threads about it yet ?

Its very common. What i have seen is the hold down clamps become loose and start to vibrate and wear a hole in the line. A buddy of mine had his truck burn to the ground because of it. I have installed the updated lines but have only about 6 months on it

The holiday is over and during that time I've found many complaints about the line. Had to use several ways to word it before I found all the comments. Seems there is a big problem with the #4 line, but until recently, I've never read anyone having this issue. Thanks for the response, and I guess I'll be ordering one soon for storage under the back seat until needed. 

At the start of this question I wrote Geno's and finally got a response, Andy wrote:
According to the Dodge Factory Service Manual, due to the extremely high fuel pressures required for the injectors, all of the fuel injector lines are the same length, and inside diameter. Because of this, the replacement should look like the original. The only difference we can see between the original, and the new version replacement is that the new version has a bracket molded around a solid rubber cushion, where the original has a blue clam-shell isolator around the line that is attached to the bracket. The current Cummins part number for the new style line is, 5289447.

Whenever I  have  the lines out on any diesel,   I  take   JB  weld  and   'build up'  the area   that is   sitting  in  in  a  support block.    I've  saved  lines  that were very thin  in these  spots...  so thin  in fact  you'd  swear  they  were paper thin.

Is  your friends'  cracking  right behind the  fitting nut,  or    up  in the support area?     I try to make sure the line  'falls' into place, before  actually tightening..  and  sometimes  a  gentle bending is  necessary to  get it  so there is  little  pressure  required to   get   both ends aligned.

 

Short lines  are problematic too,  there just isn't enough  length there  to  dissipate vibrations  and  the  movement  from  heating/cooling/vibration    puts  strain   because the  relief  loop  is  too stiff..