Archived Help, Fuel Leak

[REFLOYD]

Finished putting transmission in today and started it after being down about 3 weeks and now there is a fuel leak. Can anyone tell me where to check for the leak I have seen it drip and I am including a diagram with an arrow pointing to where the fuel was dripping from.



[/IMG]#ad




I have taken this line off and there is no hole in it. There was no signs of fuel coming from above it. the only thing that I could find was a rubber sealing thingy was kinda chewed up but that was on top of the prefilter, and as you can see the line goes up and the loops and goes back to the back of the engine. Any help is appreciated.

 

[EKlem]

There are a couple of things right around there that tend to leak fuel. The common ones are the electrical connection to your fuel preheater, the rubber line between the preheater and the lift pump and some people have had problems with the rigid lines developping cracks if they have been putting force on them. I believe that most of these parts are downhill of what you have circled in the diagram so I am not sure whether they could put fuel up there.



Is the truck running right now? If so, a large leak on the output side of the injection pump should be pretty easy to find because there is good pressure there. A leak on the other side of the pump would be harder to find. Are you having starting issues because of air getting in?



Good luck.

 

[Joe G.]

The "rubber sealing thingy" is a known problem. One member found that was his problem when he took the whole mess shown in your diagram and put some air pressure to it. When he dunked it in a bucket of water, air bubles came out that fitting.



Normally that part of the system leaks air not fuel. Another place you might check that could drip fuel there is the banjo fitting (#5 in the diagram) that is the input fitting to the fuel filter.

 

[Missouri Mule]

Possible place could be the water in fuel sensor it would be above this line.

How is the engine starting?

 

[REFLOYD]

EKLEM: no it is not running right now, the fuel linbe is off of it. I started it for the first time today in 3 weeks and it started like normal. (fired right off). I also checked ther preheater and the rubber line before i saw the fuel dripping from that line.



Joe G. : The line that the banjo fitting is on is dry as a bone. the line that I have circled is the highest point on the engine that had fresh fuel on it. we cleaned it off with brake cleaner and let it dry then started the truck and saw it dripping from about where I drew the arrow in the drawing, so we took it off and found no hole only that the little rubber sealing thingy was messed up.

 

[Joe G.]

That line is on the suction side of the lift pump so if there is a leak it should be sucking air not leaking fuel while it is running. It might drip fuel after it is shut down. What is above that line? The fuel system has pressure after the lift pump, but before it is suction.

 

[REFLOYD]

That line is on the suction side of the lift pump so if there is a leak it should be sucking air not leaking fuel while it is running. It might drip fuel after it is shut down. What is above that line? The fuel system has pressure after the lift pump, but before it is suction.

Well we know that but there are no signs of leaking above that. and really the only thing above it is the fuel filter and the return line that is back there. also as lokking at it the injection pump is just above and to the left of it.

 

[Joe G.]

You might put it up on stands. Let it run while you search around above and below with your fingers and a mirror looking for the source of the leak. Have a shop towel to wipe things to help see where the fuel is comming from. I've had to do that to find leaks.

 

[REFLOYD]

anyone else have some suggestions???? I need to get this thing running as soon as possible.

 

[EKlem]

Unfortunately, I think that Joe G has the best suggestion. I would put it back together and get it running and start looking around. If you are sure that the line you took off is not leaking but there is fuel ending up on it, it seems like the fuel must be coming from above. If it is a line that is leaking, you should have a hard start condition.



Sorry I can't provide any better suggestions. Good luck.

 

[RON'S RAM]

I would replace the rubber fuel lines to start with. They are known problems so if not leaking now they probably will. I have seen tiny pinholes that spray a fine mist onto nearby objects which makes you think they are leaking. My rubber lines had to be replaced due to leaking. Good luck. Ron

 

[Andy Redmond]

# 13 is the fuel supply line coming up from the tank. Ck. your rubber return fuel line (feel underneath the cylinder head), directly behind the fuel water seperator. If its weepy and wet a 6mm socket, 7mm socket a razor blade and about 8" of 30R7 rated 5/16" id hose will solve that problem. Fuel injection hose will last a long time, a marine hose that is silcone lined will last almost indefinitely. Its easiest to access the line with the fuel water/filter canister removed two M8 bolts (w 10 mm heads at the intake).



Also ck. the bushing in the preheater, to assure its not loose.



Do you have an aux. bed mounted fuel tank, if so, is it full and is the the switching valve selecting the aux tank, if so, enough pressure may exist to cause a leak with/w/out the engine running?



The rubber seal inside the compression nut is bad about tearing after along time, also the one to the right of the "10" in the diagram will leak fuel too.



I thought I had a part number for those seals, but I notice that I have a couple of those lines in inventory and they have the seal with them, so the bad news might be to purchase the line. I'm betting a call to cummins with your engine serial number is most reasonable. You might mention the diagram number in the bottom right of the QuickServe illustration, they will likely be unfamiliar with what you seek.



Good luck and let us know what you find.