Have a 1968 307 Chev. Cu In in my 1931 Ford. Have developed a problem while starting. Have changed the starter with same difference. Problem is that I have to jump the starter solenoid the first time to get it to start at the key, after the first time, it starts fine. Any help?
Make sure the wiring from the battery to the solenoid (and to the starter, if applicable) is beefy enough to feed the starter! It should be 4-gauge for many applications.
I have been fighting a similar issue with my '65 Impala and strongly suspect it is high resistance contacts in the key switch. I haven't gotten around to actually changing it yet as body work is currently top item on the menu, but I would consider swapping that out. Also make sure you have good ground straps with good clean connections between motor, body, and frame