Hey there, I am completely new to diesel engines, but I have learned a lot in a few days trying to figure out whether my family's latest purchase was a complete failure.

Everything seemed alright, I never looked at it, but i have experience fixing and maintaining a very fun high compression N/A gas automobile, and I think that they were kinda counting on me to be able to fix anything (which I can, but I need help from guys like you )

Well, they brought it back from getting new brakes and said it stalled out while going up a steep hill. I looked under the hood, noticed oil leaking from the valve cover gasket, the oil filler cap and/or the vent hose, couldn't really tell. I pulled the air filter and it looked pretty new but half of it was covered in engine oil, probably from the vent hose.

It sounds great though, idle seems a bit noisy but when given gas in neutral it purrs like it should and the turbo seems to be functioning properly. Exhaust smells clean, slight black smoke after being run for a little bit, and slight white before it warms up.

Next time they brought it back they had no problems, but when i looked under the hood again I noticed that every fuel injector was leaking and some at the pump as well.

My research would tell me that this is most likely a clogged fuel return line, and possibly a pressure relief valve problem and those should be checked first.

My questions are which is the return line and pressure relief valve, so i can check them? and might a clogged return line cause the oil leakage problems as well? Also if there is any other speculation on potential problems, have at, I'm all ears!

I am competent at gas compression testing but I dont know how the process works for diesels but I'm willing to go there, just to be sure there aren't major issues. I also have a vacuum tester/ fuel pressure tester, but i have never done a fuel pressure test and apparently there is no vacuum test for diesels! Please, just give me some starting points, and some pictures. I need to get this thing running right as cheaply as possible for my family.