What does the"O" rings on the crossover tubes seal?  Do they seal oil or fuel?

Fuel.

Be a bit exact. It the return fuel rail in the head. The crossover tube o-rings seal the return fuel in the head. Not lot of pressure.

Thanks, just wondering if that could of been part of my hard start problem.

Yes its possible. If there is fuel weeping out. Is there fuel leaking at the banjo at the back of the head. Last spot is the return tee at the back of engine.

I just replaced the seals on the return and the " T" ,. replaced fuel lines from the tank to the VP.  Also relocated The pump to the frame.  It is working great now #2 injector was still leaking a little replaced the "O" there,. Parked it on the stone pile nose up and it started this morning the first turn at 22*.  1/2 inch line all the way to the tank FP stays at 17.

Thanks for all the help

Do the seals you need for banjo and return tee come in a package from Cummins or do you guys take the seals with you and say, 'please sell me these o rings and this size sealing washer'? It sounds like it is 3 parts or pieces. 

 

Obviously never done this to either of my seconds, but getting very close on the 200k miler.

 

Thinking of laying an old mattress or something over everything to make it a painless job while laying there. Not sure.

Return tee seals, yes, is Cummins part.

 

Crossover o-rings can be picked up many places like DAP has them. 

Can someone remind me why a return fuel leak causes hard starts.

you loose prime and all the fuel drains back to the tank if you have an air leak in the return line.    Kinda like holding the tip of your finger on a straw while in a glass of water and removing the straw.  If you break the seal then the water runs back into the cup

27 minutes ago, Me78569 said:

you loose prime and all the fuel drains back to the tank if you have an air leak in the return line.    Kinda like holding the tip of your finger on a straw while in a glass of water and removing the straw.  If you break the seal then the water runs back into the cup

 

Good explanation of the issue. When the air leak occurs its the pressure side that let's go and returns to the tank. The return rail typically drains out anyways but there is no way for air to enter a sealed system. Following Nick's quote, the return line leaking air in the fuel will drain out the injector lines and the VP44. Now like my truck I'm lucky I've got a mild fuel weep on the 4 to 6 area that keeps the manifold damp but for some reason, it's not allowing air to get back in the system and cause hard starts as of yet.  

I got all my parts from Geno's and everything fit perfectly.  The banjo bolt is not that hard to do my problem was I just had rotater cuff repair and the only arm you can get in there is the left, I didn't have the power to get it tight, the neighbors are good when it comes to stretch.  Sure makes a difference.

OK I get it now, it's not so much return fuel leak in the head but rather draining out VP. Because both lines T in at the back of the head. 

After I relocated my DDRP wish I would of did it earlier FP is solid17 now, I haven't had the 680 hoe behind it yet. Hope it stays this way