Well, everyone has to start somewhere. Doubtless I've broken every rule by starting a thread about something which has surely been discussed elsewhere, and if so I apologise - my search capabilities leave a lot to be desired.

To the crux of it then. I have a 1981 Series III 88" with a 2.25 diesel engine which I installed just over a year ago. Obviously, I bought the engine second hand, but it came from a very low mileage 1984 ex-navy short wheelbase. It starts very well and ran very sweetly at idle to begin with. It soon became apparent that all is not quite as it seems. When you're driving there is a very harsh metallic tap on one cylinder (not sure which).

The extent of my work so far has been; compression checked (quite low but similar on all cylinders - around 195 PSI vs 400 odd in the book), head off, valves re-seated, head gasket replaced, distributor pump rebuilt, lift pump replaced, fuel filter replaced, pump timing adjusted, tappets adjusted. All this to no avail unfortunately. Interestingly, ran very sweetly with the old distributor pump installed - was only removed and rebuilt by a local diesel specialist to try and get it through the MOT as it failed on emissions. £450 later, I have more black smoke than I did before and with timing set correctly (with DTI) it still appears to be over fueling. This seems to have made the tapping worse, and the engine now sounds very harsh and 'fluffy' around the top - like you'd get when a head gasket blows between cylinders. Adjusting the distributor pump by eye - or nose - will make it run sweeter by turning it back, but then it hazes white/blue at tickover and under load it's just as bad if not worse.

I work for a Land Rover specialist in Dorset and we're all a bit puzzled by what could be causing it. It has been suggested that the timing could have jumped a tooth but what do all you wonderful, knowledgeable people think? Any advice or feedback would be massively appreciated as I'm running out of options. Also, I'm really not keen on swapping it out for a later engine like a 200Tdi as this ruins the original feel of the vehicle for me. Plus I like the fact that it's ancient, slow and generally awful. Adds to the charm in my opinion.

Thanks to you all in advance, and anything I've done wrong forum-wise, please let me know and I'll know for next time. Cheers, Tim.

id check cam timing first using dti on no1 exhaust and checking it ,before just before fully open and mark position then just after (same postion on dti )and mark that ep should be half way between the 2 marks ,pump might not be right even though its been done ,check injectors ,you can feel if cam followers are catching by placing a finger on rocker while engine ticks over,you be really lucky to get anywhere near 400 psi on compression test even with a new 2.5

HI Tim welcome to LZ

Similar problem on my 84 diesel when I got it, i think you may have a dodgy injector, to locate the tapping noise, with engine running slacken off the injector feed pipe at each injector in turn which will stop that injector working, if the noise is still there tighten it back up and move onto next one.

when you come to the suspect one(tapping sound stops), you could remove it from head and reconnect up to injector pipe to check spray pattern, the problem on mine was a solid jet of fuel not a fine spray.

i would take it back to garage if youre not happy after paying that much

good luck

Thanks very much indeed to both of you for your replies.

James, what sort of figure do you think would be normal compression-wise? I was sort of expecting somewhere around the 250 psi mark or is this being unrealistic in practice? Re-ran the test with minimal improvement after doing a top end tidy up and head gasket. Both tests were done with the engine warm I should add. Also, can't seem to read any timing marks on the flywheel? An older 2.25 diesel belonging to a friend has them (3 bearing) but mine is a very late '83 unit with metric head and 2.5 type glow plugs. I have read elsewhere that the marks were not present on later 2.25's but this could be misleading. Either way, very helpful and I'll have another look this weekend.

Steve, I removed the injectors and gave them to the same diesel specialist at the same time as having the pump done. They commented all were producing an acceptable pattern and 'squeak' but I wonder if they missed a dribble on one or perhaps a pin sticking open? Not sure if this is easily spotted with a standard bench test in a cabinet. This would certainly sound about right since the noise can be quite intermittent. Occasionally it appears to disappear altogether on the motorway, only to return a mile or so later. If it was mechanical, it would be more likely to be constant wouldn't you say? Slackening pipes off would also be a good way of testing, but it is only really prominent when you're pulling in gear with the engine under load. It's barely noticeable at idle or free revs, particularly over the rest of the clattering going on.

A colleague at work has a smokey old 3 bearing that runs far sweeter than mine, despite having covered big miles with the pump slots filed out etc. I really am out of ideas! Never mind, picking up a temporary engine this weekend so I won't be without it while I try to find the issue with the old one. I think it just needs a good going over and starting again.

If anyone's bored enough to be reading this far, hotspots are all tight in the head with no evidence of them marking the block or head gasket when the head was removed so I'd say that's ruled out too. Thanks again in advance, Tim.

200 ish depends how you do,it how good starter etc is,id be looking at pump or injectors.i have some bench tested fine but poor in practice,can you borrow some to try ,when testing injectors normally you test for leakage as well ,but ieven new cars have warrenty issue so you can expect older recon stuff to have too

Low compression, worn piston rings?

Mix 50/50 sugar and diesel that should stop your problem

Hazeltine said:

Mix 50/50 sugar and diesel that should stop your problem

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By stopping the engine?

storm99 said:

By stopping the engine?

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It won't be harsh any longer though