Your best option obviously is compression test. First cold, dry and then wet, then when hot again dry and then wet. In the absence of the necessary equipment there are still a number tests you can do that will give a very good indication of the engines condition.

I’ll just mention 3 of them here:

1) Idle.
If the engine has a smooth even idle when cold (no missing) this is very good news. This tells you that the pump calibration is 100%, the injectors are at least reasonable and there are no SERIOUS compression problems. Next push back the manual STOP lever slowly letting the revs decrease until it finally stalls. If it keeps firing smoothly on all 5 better news still! A rough idle is not necessarily bad news, could be just one bad injector or pump cal.

With engine hot and idling crack open each injector pipe in turn and retighten. The rough idle when you do this should sound the same on all 5 cylinders.

2) Blow-by.
a)First check that the breather pipe is securely connected to the rocker cover and induction manifold – no leaks
b) With engine hot and off remove oil filler cap. Wipe cover clean and smear grease around the filler hole. Take a piece of thin polythene sheet ( an old bag is fine) and lay over the filler hole sealing with the grease. Start engine and let idle. The sheet should not have blown off. Now increase revs slowly to about 2000 and the sheet should now progressively be sucking into the engine indicating a negative crankcase pressure. In other words the manifold is sucking off the blow-by faster than it is leaking past the pistons. Obviously blow-by vol. increases with engine load but should never be positive.
Briefly if the sheet blows off you have excessive blow-by and consequently poor compression.

3) Oil control rings.
Find a hill steep enough to over-run the engine at 50mph in 3rd gear (2nd for auto) preferably about ½ mile long. Accelerate away on half throttle at the bottom. If you see blue smoke in your mirror you got a problem!!

The 617 engine will give you fantastic service if you look after it -but everybody here knows that don't they? My ’82 300D manual has over 670,000km on the original engine, burns 1 ½ pints of oil to oil change at 5000km and still gives me 7 litres/100km – still as good as the day I bought it!

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Beagle