Very good advice.
If that doesn't fix it. I think the 17a still has a plate on the side of the injection pump housing that you can remove and watch the plungers go up and down.
If you have one stuck up, it will have the rack locked and that will be a big problem if you were to start it. Spray the stuck one with WD-40 or similar and pry it gently back down and up etc until it works freely with the spring keeping the lifter on the cam at all times as the engine rolls over. The rack should also move freely back and forth. If not, gently work it loose while spraying the bushings on either end of the housing.
Is the engine missing on that cylinder ????