1990 f250. Just put the 302 in and can't even start to get it running, due to some sort of ignition problem. The truck at first was turning very slow, and sometimes not at all. We replaced one corroded starter wire and the rest are new. The truck turns a bit better but not near enough to start it. If you jump the truck it seems to be better at cranking. Is this the starter?

 

I bet your Ground wire is all corroded and the connection to the Block is poor. I just put on a new 2 Ga wire and Mine is really chippy. When removing the stud, clean the block and stud well, as well as the Ground Lead. Make sure it is not corroded on both the Top and Bottom terminals. Apply some Di-Electric Grease to the Terminals prior to reinstallation. Good Luck.

 

Does it have to be grounded to the block? I had it grounded to the alternator bracket, and then to the headers just to make sure the ground wasnt the issue