OK, so I'm posting this for a friend. He has a '89 F250 with a gas v6 and recently developed an issue where it wouldn't start. I gave him a hand getting the ignition coil changed because the coil had gone bad and managed to get the truck started by shorting out the coil to turn the engine over with the key on.
However the truck still will not start using the key. With the key in the on position the ignition wire shows 9.5v. In the start position the voltage does not change but the lights just slightly dim at the dash but JUST slightly.
The backup lights do not work any longer neither does the cruise control.

He's thinking that it's possibly a fusable link and is currently looking for a bad fusable link.

 

I think your terminology is off. Are you calling the ignition coil the thing on the pass inner fender that sends power to the starter? (Starter relay or solenoid) What "ignition wire" are you checking voltage on? It sounds like your problem is that when you turn the key to start, the engine won't turn over. Is this correct? Is this a manual or AT?
Doesn't matter much but I don't think he has a V6, but in inline 6 (I6).

 

It probably is a I6 and yes the starter relay/solenoid. The wire that should provide power that causes it to give power to the starter is not firing the solenoid as it should.
It is a automatic

 

AT with OD (E4od) or 3 speed (C6)? could be the nuetral safety switch. If it has a C6 it is on the drivers side of the trans where the shift lever mounts. You can bypass it by unplugging it and jumping the 2 red wires with the blue stripe. I'm not sure if the E4od is different. Another test, one of those wires should have power when the key is in start.

 

Before doing all that^^^, try jiggling the shifter lever around and starting it in nuetral instead of park.

 

Tried jiggling the shifter, there was no go.
Would that safety switch cause the backup lights to not work as well?

 

Yes, it could

 

good to know, I will relay and have him take a look at that.