1971 e300 starting woes

Ok so I bought a 1971 e300 a few months back. It had been sitting a while. It would fire right up but wouldn’t stay running. I dropped and cleaned the tank, replaced the fuel pump and carb. So somewhere in the process I put the battery cables on backwards and toasted the starter solenoid. I put a new one on and now it won’t start with the key. If I cross the solenoid it will crank over and most of the time the starter will then not disengage until I unhook the battery. I’m am struggling on this one. Do you think it’s the ignition switch? Please help.

You may have blown a fuse or burned up a fusible link. You might also have your starter solenoid wired wrong. When you turn the key it sends 12 v to the "s" terminal, which energizes the solenoid. You should see 12v at the S terminal when you turn the key to start. To add fun to the project, some solenoids have the terminals switched from the original, so don't assume the one you bought was exactly the same as your original.

Here's a discussion that might be helpful solenoid discussion

So I’ve determined I’m getting power from the battery to the solenoid but can’t get it to go through the solenoid. I will continue to trouble shoot that issue. My big issue now is I can cross the solenoid and it will turn over but it won’t stop cranking till I pull the battery cable. Any ideas?

We'd be glad to try to help, but this forum is for 1961-1967 Econolines.

You might try posting here: https://www.ford-trucks.com/forums/forum128/
Someone there might have a 1971 with the same issue.

We can help,,,,,,,1st of all tomorrow night this post will be moved up to our Early Enough section for old stuff,,,,,,,in the meantime, take the little wires off the relay and jump the 12 volts, one at a time to each one to see if the starter cranks,,,,to test if the wiring is correct on that relay, remove all the wires and take an ohm meter and check for continuity from a big post to a little post,,,,the ones that are connected go to the starter and coil,,,, the other 2 are for the battery cable and key,,,,,you want to see if the relay is good, the correct one and wired right,,,,,,and we are talking about a starter with only a cable from the relay going to it and not one that has a solenoid mounted on the top of the starter, right?

You may have the S and I terminals backwards on the solenoid. In that scenario when the key is in run it would keep cranking the starter b/c you would be feeding the 12v run signal to the s terminal via the coil + wire.