12HT getting better economy as it gets older? (1 Viewer)

[Greystroke]

Hi all. Been about 150k km since the last engine rebuild, the old girl is running a little weird again, hoping someone can shed some light. 12HT engine, the last month or so it has been progressively sounding noisier and running rougher, but at the same time getting better fuel economy (3 weeks ago at 12L/100km now at 10L in the same conditions)!? Not something most people complain about but it's making me wonder what the cause is. It's developed a bit of a lumpy feel too, sort of like a faint miss, possibly new injectors needed. Also seemed to have stopped using oil as much as it used to. Definite power loss though, running at 10psi but feels like 2. Hopefully someone might have some clues.

 

[gerg]

Getting starved of fuel? I'd replace your fuel filter.

 

[Greystroke]

Oh wow just re read my post, I must have been tired when I wrote that, it hardly makes sense. Replaced all the filters only 500km ago, maybe I got a bad one, will try replacing again. While I were there I also checked the inline mesh filter at the pump, was clean as the day I bought it so doesn't seem to be any big things floating around in the tank.

 

[ozcrusier]

Have you drained the water trap they can fill with crap and slowly block the fuel flow.

 

[Greystroke]

Checked it about 10k km ago was clear, check again today was clear, no water. Now I'm noticing an almost metallic rattle coming from somewhere around the turbo unit. Seems to be fair bit of play (maybe 1/2mm at most) on the turbo shaft itself, but only laterally, nothing in or out. Can't find any reference material for the CT26 to see if this is within spec.

 

[mudgudgeon]

a little lateral shaft play is normal for the CT26, if you have any play in and out, check it for spec carefully. axial play is potential fatal to your turbo and possibly engine.
is there any sign of contact between the compressor wheel and the housing?

In regards to loss of power, my first thought was air in the fuel lines?
have you tested for this? If air is being sucked in it can definitely cause a "miss" or rough running, and loss of power

 

[Greystroke]

No signs of contact, the blades are are not burred and no grooves anywhere. The sound is suspiciously similar to this video of wastegate rattle so I'm hoping this may be the culprit and not something more serious.

As for checking for air leaks, I'm assuming I just replace all the fuel lines with clear

 

[Greystroke]

In relation to the wastegate, the boost isn't erratic but does seem to take a bit longer than I remember to spool up.

 

[Greystroke]

So I've cleaned it up a little bit I believe. Turned out to be a vacuum leak and a slightly stuck waste gate. Might have to start looking into new turbo units anyway, this one is getting on a bit.