fuel in oil 706D

Hello Again. I'm still trying to find the cause of fuel in the crankcase after the engine has been run for several hours. 282 engine with the roosa pump. I've had a tech from the company who rebuilt the fuel pump out this morning to inspect the fuel pump mounted on the tractor. he asked me why the return line was returned to the bottom of the fuel tank. I explained that it came that way. He stated that this could cause pressure from the weight of the fuel in the tank which might cause fuel to bypass the ip shaft seals. Looking at the diag. in the caseih online parts catalogue, the elbow nipple appears to be attached to a tube/pipe going into the tank. The picture does not show the length of the pipe. Does this tube terminate at the bottom of the tank or the top of the tank. I know that I have about 7 gallons of fuel left in the tank and when the return line is removed from the pump, I get a solid stream of fuel. Is this correct. I also found in the trouble shooting section of the operators manual that iol dilution could be caused due to excessive high idle. I have adjusted the throttle control linkage but I still have some problems setting low idle, got to jiggle/manipulate the lever to obtain the engine speed. They took the pump to pressure test it. I greatly appreciate any suggestions, spent alot of money on the engine rebuild. so far I have 64 hrs on the engine and changed the oil 5 times already. each time the level is at least 1 inch over the full mark. When I first caught it I had at least a gallon and a half more than the 7qt system after draining.
Any help appreciated.
Mike

I don't know much, but if your 706 is like my 560, the return fitting on the tank bottom is a check valve. The ball can stick shut and the engine will die. Guys will just remove the ball and things run fine. My first thought was the opposed rubber seals on your inj pump drive shaft are leaking? This would allow fuel to go straight into your crankcase. They can be damaged during pump install. If your trouble is happening while running, it couldn't be the return line since it has to pump fuel to the tank or else she won't run.

One more thought. Did the opposed seals accidently get put on in the same direction?

Return fuel line on bottom of tank is correct, and they did have a check valve in them. This does two things, one is keeps fuel from running(usually drip though) out of tank when you remove return line and it also creates a little back pressure in pump body for better cooling of pump. They seem to run just fine without a check valve though and if it plugs it of course will not run as the pressures equalize on both sides of pumping plungers and they will not take on any fuel. I have seen engines fill crankcases from missfiring, some with bent push rods, very loose valve setting and or badly leaking injection nozzles. This usually happens on a combine engine where operator does not detect a missfire . There are no other places to get fuel in crankcase, has to come from pump seals or through the nozzles. If worse comes to worse, I would fill fuel tank, pull pump off with drive so seals are intact in the housing, fuel supply and return lines on and let her set to see if fuel comes out of end of drive housing.

The weight of the fuel in the tank will exert less pressure on the pump housing than a return line that enters the top of the tank. The pressure is determined by the height of the fuel level above the pump. The amount of surface area of the fuel in the tank will not affect the pressure in the line. A fuel return line going to the top of the tank will always be filled to the uppermost part of the line. A fuel line returning to the bottom of the tank will have a pressure dependent on the level of fuel in the tank. A check valve in the lower tank fitting can increase the running pressure of the pump.

The pump should be sealed to hold the pressure the charge pump develops, somewhere around 60 PSI. I would look for wear in the pilot tube where the seals ride. If the tube has been replaced and not installed with the correct sealant it is possible that the fuel can leak between the pilot tube and pump housing.

Thank all of you who gave me direction. pump checked out good, the pressure tested it at 30psi and it held. I removed #1 injector to verify TDC and installed the injector pump and ddecided to check the #2 injector pre cup position. it was still in the 2 O'clock position (should be 6 O'clock)and was supposed to be corrected during the last repair. I believe this situation causes misfire and cylinder wash-out; is this so, this could be the cause of fuel in the oil. Was told by the repair shop the could not remove the cup so they left it alone. Will penatrating oil and a small slide hammer do? I have'nt tried yet, looking for someone with greyer whiskers than mine.