2000 cummins leaking fuel @ crossover tubes

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parkland

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I'm trying to help a friend out on this situation.

The lines are leaking fuel, where they tighten on to the crossover tubes.
I have to admit, I'm not familiar with crossover tubes, nor did I know they existed 5 hours ago.

How do they connect to the injector? And how does the fuel return work?

We tried lossening the clips that group the lines together, and tried loosening and re-touring the lines, moving one way or another but fuel is still leaking out around where the line bolts onto the crossover tube sticking out of the cover.

Also, weird part, the fuel doesn't just drip out of the fitting, there are air bubbles.
Could the crank case vent be restricted? you can see vapor coming out of the vent tube??

He says it never leaked until one day, ran out of fuel, and loosened them to try and start it again, to purge air out.
What is the answer here, remove crossover tubes, inspect, replace if burred, new o-rings, and re-install?
The fuel and bubbles are coming from around the threads of the crossover tube.

And just curious, how do the crossover tubes connect to the injectors? o-rings?
 
Transfer tubes are a pressure fit, meaning that the injection line itself provides the pressure to seat the tube to the side of the injector. The tube is conical shaped so to speak.

The transfer tube will have an o/ring. If the 19mm fitting is leaking then the o/ring is to blame. Remove the tube replace the o/ring, lightly lube the o/ring a reinstall and Torq fitting to proper spec.

Now with that being said the line itself could have a small crack at the ferrule that meets the transfer tube. If this is the case the fuel will be leaking out in greater fashion.

Small leak it's the tube....

Big leak it's the line.
 
MAXTORQ said:
Transfer tubes are a pressure fit, meaning that the injection line itself provides the pressure to seat the tube to the side of the injector. The tube is conical shaped so to speak.

The transfer tube will have an o/ring. If the 19mm fitting is leaking then the o/ring is to blame. Remove the tube replace the o/ring, lightly lube the o/ring a reinstall and Torq fitting to proper spec.

Now with that being said the line itself could have a small crack at the ferrule that meets the transfer tube. If this is the case the fuel will be leaking out in greater fashion.

Small leak it's the tube....

Big leak it's the line.
Click to expand...


OK so I'm looking at the transfer tubes, they have an o-ring on the outer body to seal the hole going into the cover, but that o-ring just keeps oil in, and dirty air out, right? Nothing to do with fuel?

Isn't it the line on the transfer tube where the actual fuel leak is originating?

But I'm also curious, why the fuel is bubbling out of the threads, not just leaking.... it must have a pressure buildup in the valve cover, along with bad body o-rings on the transfer tubes right?

Is there an o-ring on the line where it screws on to the connector tube?

Its injector #1 and 4 i think.
4 is weeping, 1 actually drips a bit.
 
Those go into the head. Not the valve cover just an FYI.

And as per cummins service manual. The cross tubes are single use only.

Ok. I know guys retighten them and reuse them. I get that. More often than not get away with it just fine. But the cross tube is made of a slightly softer material than the injection line and injector body. So it's full intention is the crosstube deforms slightly when the nut it torqued. That creates the high pressure seal. Takes up the imperfections. Loosening and Retightening changes the seal surface. The more times you do that the less likely it's going to seal.

That's not to say your injection line isn't cracked though.
 
Are you pushing the tube into your injector with one hand while you are tightening the injector with the other to make sure that when you tighten the injector that is it aligned with the tube? Sounds silly, but I've pulled tubes/injectors in my old truck over a dozen times and not once had a leak. $.02
 
Correct method is to have the injector loose in the head no hold down on top. Then insert the crossover tube pre-tighten the crossover. Then Install the injector hold down and tighten to its torque spec. Then finish torquing the injector lines down.
 
Also, the o-ring seal on the cross over tubes seals/retains the low pressure return fuel in the head. The fuel eventually comes out a fitting at the back of the head and into the external return lines. Bad o-rings will leak fuel because the return system is under 10-20 psi of pressure.

To go into further detail, the crossover tube mates with the side of the injector and direct high pressure fuel down through the body to the nozzle. A certain amount of fuel comes up past the injection nozzle's center needle/guide and runs back up a center passage in the middle of the injector. There is then a small port on the side of the injector body near the middle that spills the overflow fuel out of the injector body and into the return fuel gallery build into the head. The top of the injector body has an oring to seal the injector body to the head on the top side, the bottom of the injector is sealed with a copper washer that seals both fuel above the injector tip and combustion gasses down below the injector nozzle/body nut. Essentially there is low pressure fuel surrounding all (6) injectors, crossover tubes, and a passage running to the back of the head where a banjo fitting transfers the fuel into the return system lines/plumbing.
 
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