I've been working on a 87 240 for a few weeks now and its still not running on cyl 4, but heres the strange part: its getting a strong spark on #4, the #4 injector was replaced and its getting fuel, the compression is at 175psi on that cyl, and theres no noises coming from the engine to suggest a floating valve. any ideas?
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restored 1980 264 diesel being modified for a b30, 1967 1800S, and 73 1800 ES

Is it mis-firing badly only at idle, and worse when warm? You may have an intake manifold gasket that has been pulled in on that port. Try feeding some acetylene or propane gas, or WD-40 to the intake runner at the head on number four. If the engine picks up instantly, you have found the problem.

IF you have spark, compression and fuel at #4, how do you know it is not running on #4? Fouled spark plug? Maybe it's a bad plug?
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Gary Gilliam Sumerduck VA, '94 940 na Regina 150k, '86 240 180k

I know its not running on cyl 4 because its running rough, and when I unplug the #4 injector it doesnt make it worse, I've already replaced the spark plugs as well as a intake manifold gasket.
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restored 1980 264 diesel being modified for a b30, 1967 1800S, and 73 1800 ES

Pulling the injector plug is not a good diagnostic, pulling a plug wire is. All injectors on the B230 fire at once, the fuel vapour stays in the manifold until that cylinder goes to intake stroke. When you remove an injector there is still fuel vapour in the manifold from the other injectors so you will not necessarily see the dramatic change in the running as when you pull a plug wire. How much of a change will depend which injector plug is pulled.

Having said that have you tried swapping the injector plugs from say 4 to 3.

You do not state the problem except to say not running on #4, to me that is a questionable diagnosis. Can you describe what is actually happening.
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David Hunter

ok, the engine is shaking excessivly, there is a lack of power, and the exaust manifold is cold coming right out of cyl 4.
and yes I have switched injector plugs, but the problem still stays in cyl 4

If that is the case (spark, fuel and compression), then you must have some unusual situation, or one of the new parts ( plug,intake gasket) are bad.

That would suggest a spark that is too weak to ignite the mixture, bad wire or plug. A catastrophic cam failure , like a totally wiped lobe or a breakage. Or bad rings, that are oil fouling the spark plug.
What does the #4 plug look like when you pull it after it has run? Dry ,or wet with gas or oil? Carbon,soot covered?
My money is on a wonky wire.
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Gary Gilliam Sumerduck VA, '94 940 na Regina 150k, '86 240 180k