I just serviced the fuel system on a recently acquired Hitachi Ex 120-3 and in doing so changed the fuel filter, cleaned the screen and emptied the fuel separator. The prior owner had an inline electric pump that I activated to prime the system. Days later the fuel separator was found leaking so I replaced it with a new one and then primed the machine again. After a couple days use (2-3 hours each day) I noticed the exhaust was spitting black residue - a lot of it. The machine has no loss of power and the turbo seems to work fine. I checked the oil and noticed it appear thin And not as black as it should be. The machine has about 20 hours since its last oil change. Although the level was at the full mark, when I pulled the dipstick, there was oil residue in a couple of places higher…that I thought was odd. Could I have over-primed the fuel system and somehow contaminated the oil? The turbo shows no obvious signs of leaking. The machine has 5600 hours. It is an Isuzu engine. If contaminated oil, is this simply change the oil and filter and see if it still spits residue or is there something else I should look at. I checked the oil pressure exhaust that typically comes from the valve cover but it did not show any obvious signs of being over pressurized. None of the turbo lines appear kinked and the air filter was recently replaced.
That electric pump may have pushed a leak at the injection pump seal. @thepumpguysc is our resident pump master and he may have the answer for you. That is the direction I would lean but I know next to nothing. to check the oil for fuel, pull the dipstick and put a drop of it on a paper towel. As the fuel evaporates it makes an obvious clearer area around a darker oil spot.
Thanks. I tried your suggestion with the paper towel but didn’t see a material difference so I am not 100% sure diesel is in there. Another thing I forgot to mention is that I built a fuel polisher and removed as much of the fuel as I could then drained the tank. There was a lot of crud on the bottom. When I put the fuel back in I added quite a bit of additive to clean the system. Could the oil spots I am now seeing be soot, etc. Just before my latest and most obvious signs of spots everywhere I pumped in a bunch of fuel. Could I have stirred up the remaining crud and that’s what is coming out the exhaust? The stumper is I did not have this issue before cleaning the fuel system or at least I did not notice it.
I'd be looking at the turbo. If its wet at the outlet but not the inlet I'd say the turbo is on its way out.
The oil out the exhaust is likely a coincidence. Once you get the turbo fixed, you will discover another expensive coincidence. Maybe a broken piston ring. Then, it will start overheating coincidently. Then, a hydraulic line will break and you will drop 30 gallons of fairly new oil, on the rhubarb. Keep us posted.
By chance does that electric pump have a psi rating.?? U don’t need more than 25psi.
I'm assuming that's an inline kiko pump, so it operates at a pressure that should be higher than any electric priming pump. You said it's blowing "black residue", that you suspect is fuel or oil, and the oil is thin and not black enough. Sounds all normal to me. I'd get a ten pack of SOS oil sample bottles at the cat dealer, and take an oil sample and send it off, that will reassure you it's fine. Or it could blow up like Coaldust says, we always like pictures when stuff blows up. Take a hydraulic oil sample also so you don't change that needlessly, check the level in the final drives, plan to change the final drive oil, don't bother sampling it because you don't want to know.
So the electric pump label reads 10 psi. We cleaned the residue off and have run the machine for a few hours the last few days…no residue has returned. The muffler is new within the past year and I noticed the stack doesn’t have much of a curve to it. Given all the rain we have had we suspect rain water got into the muffler and the residue is somehow related. This may be wishful thinking as of now we aren’t seeing continued problems.