Not all that horribly long ago I had a '94 Firebird with a 3.4 & a year or so after I bought it the starter took a crap so I bought "the very best that Advance had" with a life time warranty, & two more of those crapped out on me also. (And that POS Pontiac was a PITA to replace starters on.) But where I am going by reliving the painful period of that vehicle in my life is to say that I don't think that the quality of a lot of replacement parts is very high a lot of the time. As a matter of fact, I'd say in the case of those starters from Advance, the quality was pretty low.
I think it is possible that your problems simply come down to the quality of the replacement starters that you are getting.
And on edit, rereading your post, if you are starting it by jumping across the large terminals on the starter solenoid, I believe that is a bad starter solenoid on the starter itself. You could check that with a meter: if you are getting voltage to the solenoid (at the small wire) when you have it cranked, but no voltage is getting across to the starter motor, I believe that would mean the solenoid had failed.
I think it is possible that your problems simply come down to the quality of the replacement starters that you are getting.
And on edit, rereading your post, if you are starting it by jumping across the large terminals on the starter solenoid, I believe that is a bad starter solenoid on the starter itself. You could check that with a meter: if you are getting voltage to the solenoid (at the small wire) when you have it cranked, but no voltage is getting across to the starter motor, I believe that would mean the solenoid had failed.
