I have battery voltage at the main relay. If I jump the main relay it starts and runs great. I bought a new relay (duralast $112.00) installed the new relay and won't run. Jump the main relay and runs like a champ. I have a new distributor (duralast $180), new coil, plugs, and wires. I'm wondering if I've lost a ground somewhere or maybe it's a bad ecm....

 

Does the starter spin the engine with the ignition switch?
Do you have spark when this is happening?

 

Have you ever replaced the electrical portion of the ignition switch? One can have OK start circuit but the run circuit being bad.

 

any luck with this

 

Bigger knowledge base for B2600i at MazdaTrucking.com, post there.