I appreciate any help that might be offered.
This 1994-era engine
was pulled from my boat
and is in my shop. As an exercise, I am taking it apart and trying to figure out what is wrong. I have no experience with diesel
engines but have time, space and the manual.
The symptoms when the engine
was pulled are:
1) engine ran roughly with unburned fuel
in the exhaust
and much smoke.
2) I determined one cylinder was not firing using the decompression levers.
3) If I switched injectors on the non-working cylinder with another injector from a working cylinder, the original non-working cylinder continued not working and the other cylinder worked as before. Thus the injectors seem fine.
My first thought was maybe a problem with the valves associated with the rocker-arm assembly. Once I got the valve cover off, I manually spun the crankshaft and observed the valve movements. Everything looked identical on all three cylinders. No obvious problem here.
Next, I proceeded to removed the engine head
. I have attached two pictures - one shows the bottom of the head
and the other shows the pistons. The "bad" cylinder is marked in the photos.
- both parts
are covered in black carbon soot. Is this normal or a sign of the age of the engine.
- the "bad" piston has slightly different wear marks on the top from the other two but I don't know what this means.
- all three pistons move as expected when I rotate the crankshaft. However, the piston in the "bad" cylinder might not lift
as high as the other two. The other two pistons essentially are flat with the top of the engine surface at their maximum height. The suspect piston might be a 1/16th or so below this height. However, any difference is not obvious to my eye.
Otherwise - all looks OK.
Does anyone have any advice what to look for next? I thought I would probably have located the problem by now...