I have a Onan Diesel RV Generator and I need to start it automatically with my Sol-Ark inverter it is equipped with a 2 wire set of normally open contacts and the generator has a 3 wire start. Momentary on and momentary off.
From a quick search, one line is start, and the other line is stop. You may be able to use a normally closed relay for the stop line that is controlled by the start line. When "run" is requested by the SA, the Stop relay opens, and the start line is closed to request the start.
It stays in start mode until SA no longer requests the generator. At that point, start is open, and the Stop relay closes to activate the Stop line.