Fires but won't stay running

Hi everyone I'm new here as i am desperate for help! I have a Mazda b2600i 1992 4x4 pickup which other than a minor oil leak seemed too good to be true! I bought it two days ago and the previous owner replace distributor(all parts), wires, plugs, shocks, exhaust, air filter, and battery. It ran a little rough when idling at about 500rpms??? So I then adjusted and idled it up to about 800 rpms and installed sea-foam 1/4 can into the intake-1/4 into the oil- and the rest of the half of can into the gas tank. The truck ran beautifully with a very very minimal delay when touching the accellerator! Then with that "fixed" I then removed the center console and radio snipped all the wiring harnesses off and installed an aftermarket radio (hard wired). Turned the radio on and it sounds great! Attempted to start the truck bc I had the radio on for about 10 minutes and guess what the truck won't start....... Don't understand why if it ran so good after doing all the other work.... Now the weird thin is while trying to start it If you hold the key all the way forward to the start position it will run and keep running until you let off the key where the "run" position should be buy then the struck shuts off.... Checked for spark and truck does have a yellowish spark while holding the key all the way forward... My question is what the heck is the problem did I hurt the ignition or something else because of hardwiring the radio?? Did I burn something else up? Did the seafoam mess it up? I really appreciate any and all help that I can get!!!

You probably need a new ignition switch, check Rock Auto for the part, the part is about $90 and is the contact portion of the switch, the key remains the same. Do a search on the repair, there's plenty of pictures at least at mazdatrucking.com

So this doesn't have anything to deal with me cutting the radio wires you think? Or you saying I may have burned the ignition run

That's EXACTLY the same symptoms my B2200 had when MY electrical part of the ignition switch went out. So I say it's not releated to your stereo install. And just because that stereo has power in the "run" position doesn't mean that there's voltage getting to the coil in the "run" position, there are several circuits for that position. Lots of these trucks have that issue with age and use.

I'd say to check out the ignition switch electrical part while it's in the "run" position, guessing it has voltage going in but not out to the coil circuit.

You could temporarily jump from the battery positive to the coil positive terminal to show that the truck still runs when you crank and release. I'd use a wire with an in-line fuse if you did that though.

Here you go;