Here are the symptoms:
poor/loud running
shudders terribly at idle, and if I don't run it at speed for a few moments it dies completely
strange but faint 'chuffing' or 'puffing' sound from the engine bay - sounds like it's from the fuel pump/air filter area.

I've replaced rings, bearings and stem seals, and adjusted tappets, glow plugs are inoperable at the moment, so running cold.
could be residual air in the fuel system, and the timing could be out. Other than these two things I don't know where to start. I'd like to upload a video - but can't unfortunately.

Cheers,
Luca

Have you had the injectors checked?
where is the injector pump timing ie is it at end of range could be chain stretched.

Blackburn said:

Have you had the injectors checked?
where is the injector pump timing ie is it at end of range could be chain stretched.

Click to expand...

Injector pump is slightly anti-clockwise of the pointer - maybe 1mm or so. I think a local guy has a pop tester for injectors, I'll swing round and get them tested in the next few days hopefully.

If looking for a dodgy injector while running crack off an injector nut at the injector and it will stop working, if you do this to each of them in turn and there is no change to engine idle then that could be the faulty one
If you crack off a good injector it might get worse or stall.

steve2286w said:

If looking for a dodgy injector while running crack off an injector nut at the injector and it will stop working, if you do this to each of them in turn and there is no change to engine idle then that could be the faulty one
If you crack off a good injector it might get worse or stall.

Click to expand...

Okay, so 1, 2 and 3 all cause it to stall instantly at idle, with 4 it doesn't stall straight away.
Borrowing a pop tester tomorrow to test spray pattern.

The other symptom seems to be an irregular miss, and unburnt diesel smoke (stinks and burns my eyes). I shouldn't think this would be compression as that would cause a regular missfire wouldn't it?

Cheers,
Luca

Hi Luca
My old series 2286 used to have an irregular miss with a little chuff every few revs, never solved it.
With no 4 possibly being suspect you can now try swapping with one of the others and doing same test to see if the stall happens still on injector 4 but in its new position.
You can also when they are both out connect them up to pipes outside of engine by turning pipes around this let’s you compare spray patterns.

But, for goodness sake, be careful! Don't have your hands near the nozzle, injected diesel results in immediate surgical weight loss. And qualification for consideration in the second Olympic games, after the main one.

I had similar on a 2.5nad, got a compression test done and number 4 was well down on mine. Took the head off and I didn't spot it straight away but the piston crown was slightly lower than the rest. Bent con rod it was.
However,
The air filter area noise you mention...
Can you feel air blowing back out of the inlet manifold?, that makes a chuffing sound, valve(s) not seating properly. Compression test will eliminate lots of head scratching.
Circa 400psi.

Way beyond my technical abilities but I will add to the safety and caution plea. I got to watch a specialist outfit reset my injectors and they were handling the pump, pipes and all things connected as if it was a very fragile explosive device. The lead techie had gauntlets, a face shield and a rubber apron on. Take care.

So, an update.
The 'chuffing' was due to poor tappet clearance, it seems number 5 and 6 had loosened themselves considerably (or possibly the pushrods weren't seated properly when I adjusted them the first time - either way, that solved that issue).

I borrowed an injector tester, and with due caution, tested all 4. I found 3 of the 4 were pretty much perfect, opening at around 135atm (who knows how accurate the pop tester is though). But, number 4 injector (which is the cylinder that seemed to have issues) was very dribbly: when under full pressure the spray pattern was fine, but it permanently leaked fuel. I grabbed another injector from the spare engine I have which opened at the correct pressure, had good spray pattern, and didn't dribble.
and....
no change. absolutely zero. it seems to have a little more power, but smokes just as badly as ever.

to say I am frustrated is a little of an understatement, I'm going to call a local diesel mechanic on Monday, and hopefully, he can shed some light on things.
I'm still leaning towards fuel delivery/return issues as the compression on all 4 cylinders is OK (not amazing, but definitely acceptable) very high 300s, low 400s by memory, would have to check the manual again, but I thought they were supposed to be around 425 - would this be enough of a loss to produce issues? I don't seem to have any other symptoms of low compression, ie, no blow-by (worn rings), rocker cover breather doesn't puff air, and starts first rotation after 10 seconds of glowplugs, and after 3-4 seconds with no glowplugs.

I'm also thinking someone may have stuck the pump in poorly timed at some point - it's the S3 version, so they recommend a tool to get the pump timing correct when replacing, and the red gasket silicone implies someone has removed it at some point.

Cheers
Luca

Sounds like it’s not too far away now, starting good so timing can’t be far away, you can play with settings without special tool, if it’s still shuddering on tickover , could increase the idle rpm, I did this to reduce body vibration, Compression figures good, with new rings in , did you hone cylinders , these may take time to bed in and smoke might then improve

I am hoping things will improve, cylinders were honed.
The other thing is when I got it the stem seal were leaking very badly, so all the intake/exhaust valve areas were pretty oily, whilst I did clean these out as best as I could there is properly some left in there, which will potentially take a while to burn off.

Thanks heaps
Luca