Small diesels need more ether. 25% is too low for most diesels. 30% and up is better with the little ones needing 35-40% ether. 20-25% castor oil, 2-3% nitrate ignition improver, and balance kerosene.

If your diesel doesn’t start and your priming regimen is 100% spot on, then your fuel needs to be tweaked. Start with 35% ether and see if that improves starting.

I would encourage you to do some reading and research to see what fuel your engines need.