Oldsmobile/Buick Repair: Diesel Fuel Injection, diesel fuel injection, test jig

Question
My vehicle is a 1986 Chevy Suburban, 3/4 ton with a 6.2 liter diesel. It seems to have a lope at idle, like a weak cylinder, or possibly a bad or dirty injector.  Is there a simple way to test for a bad injector, without having a test jig to "pop" test them?  Or should I just replace them all and see if it helps?  

Answer
Hello Art,
There is a pretty easy way to see at least what cylinder it is.
Where the injector line connects to the injector, while the engine is running, just crack that nut holding the line loose.
A little fuel will squirt out, and that cylinder should act like you pulled a spark plug wire off.
If you have one cylinder that makes very little, or no difference, that is where the problem is.
Now, the problem could be the injector, but it could also be in the injection pump, a valve in the cylinder head not opening, or closing, bad rings, a head gasket leaking between two cylinders, or it could be a glow plug, except if it were, it would have no effect once the engine warms up.

Good luck,
Van