My son and I bought a D4 7J from a widow. "Been sitting at least 7 years", the neighbor said. New fuel lines to pony, clean out carb, and tank, change oils, and pony started! Hours later we discovered air bleeders behind injection pump feeds (buried in grease dirt) After our adrenalin pumped up with first smoke from exhaust,then 2 cylinders, next 3 shaking us and machine, we danced around like little kids when, to our wonder, four cylinders idled sweetly. Drove it on a borrowed gooseneck trailer and got it home. Now to figure it out. Changed all fluids, pumped grease zerks (even one on clutch). Engine overheated. Found a thermostat at radiator end of water pipe from engine and drilled tiny hole in thermostat to release air. No more overheating. After 2 years of playing with and fixing in not enough spare time, we need help finding why diesel fuel replaces the oil in bottom of injector pump. It holds about a quart of oil. The level goes down in an hour and whats left gets thin with deisel. Copper fuel lines connect back of injector pumps, bottom of transfer pump, tops of injectors, and top of fuel filter housing. Are all these connections factory? I read on this forum about fuel dripping out of lines in old days and wondered if one of these lines should be free to drain out. I will try to include pictures and appreciate any input. It might take me a while to respond again since I only use internet at a friends office. Thanks, Sid.

You may have two problems there.The oil may be leaking out of the lip seal where the drive is for the camshaft in the pump and fuel may be getting in from a bad "O" ring seal between the fuel feeding ferrule (tube) to the injection housing.There also is a plug with an "(O)" ring seal on it on the back side of the housing on the end of the internal tube that feeds fuel to the inj. pumps and is toward the top of the housing. The inj. housing will have to be removed to get at both the seals on the front and the governor would need to be removed to get to the rear "O" ring seal.Chances are it could just be the two front seals but not worth taking a chance while your into it.

The drain lines and fittings look mostly original but they should be open (two lines) to drain at the bottom. If you have diesel accumulating in the injection pump housing it can leak past the lifters and down into the pump sump.

Oil from the sump is probably leaking past the seal as SJ mentions.

There is an old school fix of collecting the fuel leakage and routing it into the transfer pump suction line but then you loose the tell tale feature that the drip lines were intended for and may lead to other problems

Congratulations on getting the old gal running again. It sounds like you enjoy these old critters. They can be the source of a lot of fun. .and frustrations at times. Get a set of books for the critter. .and don't be afraid to tear into it as needed. There's nothing really modern (read computer controlled) in 'em, they're really quite simple. Sometimes you'll wonder why Cat did some things the way they did but the reality of it is. .they work.

The folks on here are really good about responding to questions. .there's a lot of knowledge here to tap.

Hi Sidney,
it looks like ALL the drain lines are plumbed together, IF they are not connected back to the top of the fuel tank to drain above fuel level the end result is any injector or transfer pump seal leakage is being directed into the Fuel Injection Pump housing and will contaminate the oil within.
There are fuel pump plunger leak-by catch trays on each pump lifter to direct any leakage past the pump plungers into the DRAINED area of the Injection Pump. This area is above the oil reservoir, BUT, if the drain is blocked and the level rises about 5/8" it will then leak into the oil reservoir.
My belief is that if ALL the drain lines are connected to the Transfer Pump inlet the fuel tank level is above that of the FIJ pump and the same will occur, THERE-FOR ONLY the injector drain lines should be connected thus.
I would sugest to drain and renew the FIJ pump oil and disconnect the lower fittings shown in your pic. and run it and see what happens before I went and did the big job of FIJ pump remove and reseal. If all is OK then I would re-plumb only the Injector drain to the transfer pump inlet housing---where the main tank fuel line comes into the Transfer pump.
Hope this helps.
Cheers,
Eddie B.

Thanks for the response to my injector pump question. Sure is good to hear from people experienced with the old iron. Yes, a set of books would be great. Think I'm going to experiment with the connections of the fuel drip lines first and then maybe pull the pump off and check out those "O" rings. Doesn't sound to complicated. Working on this old girl is almost as much fun as starting it and running it. Just need more spare time!

Don,t worry about getting the housing out of time when you remove it as the drive tang is off set so can only go on one way.

It's been a few months since I had time to conclude this, but thanks again to all. I disconnected the line attached to the bottom of the injection pump housing and plugged it. Then attached another open ended line (drip line) from injection pump housing. I ran engine for an hour or so, and then checked the oil in injector pump housing. Problem is fixed. I detect no deisel in that oil now. I believe that the fuel transfer pump or injector returns were pushing fuel back up into the housing since they were all connected together.

Sounds like a good fix.
Please post of picture of what it looks like after you re-plumed it.