i am in the the process of swapping out my 3.1 to a 350. i have the ecm and wire harness from a 5.0 car. i have 95% everything hooked up and im down to starting it up. but when i turning the key on i hear no fuel pump, and starter doesn't even crank. i checked all the fusible links at the red wires after the links and they get voltage. i put power to the purple wire for the starter and it turns over. so the starters good. i put power to it all the way to the crank fuse ant it still works. and when its turning over it tested for spark at the coil and get nothing. and i don't even get a security when i turn the key on. is it a vats issue? vats worked with the 3.1 in it.

 

I'm not 100% certain here about this , so you will need to do some searching and reading in the V6/V8 swap forum , But , something here sounds familiar that the pin out of the harness where it plugs into the body (The C100 connector , maybe ?) is different between the 6 and 8 cylinder cars . As in , if your still using the 6 cyl dash & body harness and have the 8 cyl engine harness plugged into it that the connectors will physically fit together but that the connections will be wrong due to the different pin out ? Like I said , I'm not 100% certain on this , It's just something I thought I remembered reading someone else here running into during a 6 to 8 swap , so research it and see if the possibility exists of a mismatch between the connectors . Good Luck with it .

PS , don't know what ya mean by " 95% everything hooked up" , you should not even be connecting a battery to it till ya think ya got it 100% hooked up , and then troubleshoot from there .........

 

Either that, or one of the 2 (or 3? however many) fusible links at the starter, is bad or not hooked up.

Given that one fusible link powers one wire which goes to one cavity in C100 which goes to one big red wire under the dash which goes to the ign sw... all ya gotta do is start at the ignition switch and work your way back upstream toward the battery.