Only will crank when jumping solenoid

There's at least three, and maybe four totally independent switches inside the ignition switch. The most common part that fails is for the radio, power windows, and heater fan. This one fails most often when people turn the ignition switch on and off while leaving the heater fan switch in one of the higher settings. That high current stresses the contacts in the ignition switch, and it causes excessive arcing when the ignition switch is turned off.

In particular, look at the two terminals with my red and blue arrows pointing to them. Those are the two that will usually be black, or show other signs of being overheated. When you find that, the repair has two parts, and both have to be done at the same time to prevent a repeat failure. The ignition switch must be replaced, and those two blackened terminals must be cut out of the plastic connector body, along with four inches of their wires. Those wires will be hardened from being hot, and solder won't adhere to them. If you don't replace these terminals, their poor connections will cause heat build-up that will migrate into the new switch's contacts and cause them to overheat again.

Splice in new sections of wire of the same gauge, then crimp on a pair of universal crimp-style terminals. Solder those terminals to the wires too for a better connection. Once the melted part of the connector body is cut away, those two terminals can be plugged into the switch separately. If either of the terminals and wires, or the switch are not replaced, their degraded connections will cause heat build-up, and a second failure of any new parts.

The second thing to look for requires removing the lock cylinder from the switch. Remove one screw that holds the silver metal plate that's facing you, then you'll have access to the small round, silver roll pin that must be pushed in about 1/8". That lets the cylinder pop out. Look at the round unit on the end opposite where the key goes in. There's three different styles of that end, and you must have the one that matches the switch. The common failure there is that disc, about the size of a stack of four nickels, has a key way, and part of that breaks off. When this happens, the cylinder doesn't turn the switch as far as you're turning the key. Typically the accessories and dash lights turn on, but the switch won't quite go far enough to turn on the starter circuit. Turning the switch backward to the "accessory" position still works normally. I'm looking for a picture I can post for this problem. I still have the broken part from my '94 Grand Voyager that uses the same ignition switch. If I can find the old part, I'll take a photo of that and post it for you. The dealer has a repair kit for this problem. Once the cylinder is reinstalled, the roll pin will get pushed back out when you turn the switch to the "crank" position.