I think that you will find your rpm sesnor is not working. Try plugging in your EDT and then make a start cycle, look at the edt and see if the rpm comes up if not there is your problem. The ECU is looking for rpm increase before it will back off the starter and then add the gas for a richening mixture to obtain a light off. It may be just as simple that the rpm lead has become disconneted. It may also be that the rpm sesor has failed.