Sounds like you maybe having trouble with the position sensor found at the fly wheel upper left looking up from bottom hard to get out, perhaps some one can tell you if there is a test to check it I just changed mine not to long
ago.I have a 90 mod 420sel.look up some of my post on how I changed the unit,it fixed my no start problem and after much reserch and checking other electrical components it is doing very well. j-n-t