Hello all
An interesting development today with my D4 7U. I'll tell you what happened first, then what led up to it, and maybe confirm my suspicions, so I can fix it. Today, I removed the hour meter, and the cavity behind it was full of diesel. 

So, I didn't expect this, though I have been having a variety of fuel issues for awhile. This machine had been setting for many years, but I got it running this summer. Fuel pressure has been low, it drips a bit, but runs very well. Lately though, it keeps losing it's prime. And the oil level went way up. I changed the oil, it did it again, 1 gallon overfull in 2 weeks. I have long suspected transfer pump seals, but once tried to remove the pump. The collar is stuck, but I guess with enough 'persuasion' I can get it out and replace seals. 

My question is, can the fuel find a way into the area behind the hour meter from any other source?  What might cause fuel bleed down, besides transfer pump seals.
Thanks
Ron

You are probably getting fuel into the crankcase also and it can create major problems. It probably comes from a leak of the ferrule and O ring that is between the fuel housing and the injector pump housing. It can be replaced by removing the injection pump. Not a problem that should be overlooked as it can ruin an engine with oil diluted with fuel.

Well, this was the information that I suspected. To add one more observation, I noticed with leaving the leaving meter 'loose' last night, that there was quite an amount of diesel on the gravel. By the way, this has a secondary fuel shut off near the engine, since the tank valve does not fully shut off. So, I know the fuel is shut off, and the leakage is from the fuel system, somewhere. Today I ran the dozer a few minutes to move it around, and when shut down, there was again a pint of diesel in the cavity; seems mixed with oil, too. I drained it, wiped it with a towel, and a bit later it had a lot of fuel again. I dried it, and again it was accumulating diesel.

Just wanting to confirm what I am also thinking, that this is the seal by the injector housing and tower, and not the transfer pump. However, shouldn't the drain on the side of the pump drain the cavity above the transfer pump?
Thanks,
Ron

Sir I do not know a whole lot about your machine but I feel like I understand the principles of the process you described.  It seems to be siphoning the fuel from the tank while it isn’t running. And you know you might crack a fitting and break the prime and isolate the leak, maybe. But if it were simple to just take a guess and change that prong I would do it. I just wanted to share an unprofessional opinion and maybe keep the ideas coming.  I do hope you let us know what was wrong. Good luck Mike Hudson 

changhe the seals on the injection pump shaft and the transfer pump then you know its right.

You're right there! That's my plan, starting today.

Those new O-ring seals can be kind of difficult to get into place without nicking or tearing them. Be carefull or you may be back doing them again. When I did mine they seemed to be too large but they did solve the problem. 
Bruce

Hi All,
I use a proper rubber grease when I put orings back in, i have had no issues at all and makes it so easy

Regards

rocol make a good silicone base oring grease. dow corning also have a good one too. you dont need a lot but it makes life easier. and use proper seal tools not screw drivers.

Amazing, I was able to get all the parts at my local Cat dealer. WOW. Now, one question remains. A good answer might save me a lot of time. HOW is a good method to access the nut and bolt behind the injector housing? The manual makes this all sound too easy.
Thanks,
Ron