When trying to start my 1991 honda civic dx sedan if the check engine light is on it won't start. As soon as the light goes out it will start as long as it stays off while cranking. Some times have to wait up to 20 min. for light to go off. Any ideas?

The ECM is failing--guaranteed. Replace it with an exact Honda part no. match and your problem will be solved. This link will help:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post235038