how to tell if injector is leaking

try to find place washed with fuel. Less oil on metall.

If I can see I use car electric fuel pump, and push fuel from bottle to cyl head (i usually separate fuel line from delivery pump). Pump must be good becouse pressure may rise up to 15 bar and pump goes bad soon (LOL).

But if you get fuel in oil problem - just replace ALL cooper injector sleeves and ALL injector o-rings)

 

When you say under the rocker cover, do you mean lower on the outside of the engine, or did you actually take off the rocker cover and look inside? Any internal fuel leaks end up in the oil pan. If your engine is making oil that will confirm a leaking injector. Leaking injector cups usually lead to fuel in the coolant, or coolant in the oil. I can't see anything fuel related leaking like that and still looking like oil. It probably is oil. M11 are known for leaking between the head and rocker box housing.

 

No, but almost. Everything comes off down to the head. The rocker box housing is also the intake manifold. To get that off all the rockers have to come off. I think the injectors can stay in, but now is the time to take them out too and put new orings on them. That gasket isn't very wide around the perimeter and kinda like a stiff paper type. They just break down and leak. How bad is it?