Curly diesel problems

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I have a rd28 (in a laurel car, but ignore that part for now..) that I'm having trouble with.
To start with a bit of history, a mate of mine had this engine, and it went all good for him before he decided a v8 is more his flavour than the wheezy diesel. So out it came, and sat at my place for 10months or so.
My rd28 had pretty much expired ( so smokey it wasn't funny. oh wait, yea, it was funny how smokey it was hahaha), so out it came, and in went my mates old engine.
When I went to start it, I had heaps of issues, but it fired up pretty quick with a tow down the road (lucky I'd earlier converted it to manual).
Now it goes great---- UNTIL you hit about 3500rpm. Doesn't always do it, but often (usually?) does. And doesn't matter if its under full load, or just revved up in neutral.
What it does is drops a cylinder (sometimes 2), gets real smokey, and runs quite badly. To "fix" it, you just keep it running for a bit, and it eventually clears itsself, and purrs again. I've turboed the beasty, but can't in any logic see how that could cause it.
Could it be an injector seizing and stopping fueling to that cylinder?
Or maybe hydraulic tappet keeping valve open and reducing compressions?
I've checked fuelpump return, and no signs of bubbles in flow.
Anyone got any suggestions, lines of attack etc?
Many thanks,
Nathan

[sibainmud]

Restriction in the supply to the injector pump would be the first thing to check. Does it have a primer on the fuel filter housing? If it does, then get someone to pump the crap out of it while you rev it up. Another way of checking the supply and the internal lift pump side of the injector pump is to put a container of CLEAN fuel on the roof with a pipe/tube directly onto the banjo fitting on the inlet and then run it. Could also be the gauze filter under the "in" banjo bolt. Also make sure that the banjo bolt on the outlet from the injector pump is the one with the small hole in it sometimes marked with out on the head.
That lot should keep ya busy for a while

Cheers,

[Crash bandicoot]

firstly take the pipe of between the turbo and the manifold and go for a drive.

see what happens with the engine in its original N/A form.

If it was not originally a factory turbo the pump will be having supply issues. maybe put a inline fuel pump in it before the injector pump to help boost the feed to it so the injector pump isn't having to suck fuel.

From memory the RD28 commercial was a turbo and employed a different injector pump. used in the Y60 safari

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Mucked round with it abit again after work tonight.
Tried cracking injector pipes while it was running bad, seems number 4 is faulty, and one other that I couldn't pickup. (would pickup from running on 4 to 5 much quicker than 5 to 6).
Whilst I was there thought I'd better replace fuel filter as I can't remember how long I'd had it on (I write km/date on them now )
Was a bit of gunk, but no water or diesel bug in bottom of filter. Haven't yet checked gauzes.
I put some 2stroke oil into filter, and handprimed it up. Also put some in tank and topped up fuel level (was bit below 1/4)
Seemed to run better on way home, but not a long enough drive to know for sure.

Cheers for the tips guys,
Nath

maybe put a inline fuel pump in it before the injector pump to help boost the feed to it so the injector pump isn't having to suck fuel.

Have considered putting a pump in, will check gauzes first tho

From memory the RD28 commercial was a turbo and employed a different injector pump. used in the Y60 safari

Yea, thats the exhaust manifold I've used. And I have the non-turbo (no aneroid) fuel pump