Ignition switch differences

The ignition switch on my truck has been causing a crank, no start issue. I'm looking into replacing it, and they are very expensive. Especially if you buy the key tumbler with them. Not only that, but I have a 1990, and apparently they get even more expensive that particular year. I'm having a hard time figuring out whether or not the manual and automatic transmission ignitions are different, because some places advertise them as different parts, and some as the same. Anybody dealt with this before?

"The ignition switch on my truck has been causing a crank, no start issue."

Yes, the engine may crank great, then not start or not keep running once the switch is released, lots of contacts inside it, that was my issue. If the key tumbler turns (and it sounds like it does), then - like mine about 20 years ago - you need to replace the ELECTRICAL PART of the ignition switch only. I will hint that connection of the wire connections can be easier if you pull the instrument cluster out for access (for that the clip on the engine firewall needs to be released, also the speedometer connection on the FRONT of the cluster). You may need to get two tiny "push nuts" at Ace Hardware, were not included in my "kit", which was dealer-only and $103 back then, but was in stock locally.

However: you may want to try to clean and fix your existing switch, see Axel's write up http://www.mazdatrucking.com/forum/showthread.php/14502-Ignition-Switch-Exposed!

Thanks Cusser! Funny enough, I had already exploded the switch all over the place when I popped it open it took me about 20 minutes to find all the missing pieces and ball bearings. I did end up figuring out how to put it back together. Cleaned it and re-built it even though i bought a replacement at the parts store. The re-built one worked, so I'll save it as a backup. The cluster removal info was priceless, as it saved me from getting pissed off trying to reach way up under the dash to get to the plugs. Fortunately my kit came with replacement push nuts for the key trigger switch. It was 99 bucks for the new switch. The truck seems fine so far. I hope that was the real issue, I hate getting stuck!

Good. I didn't know the cluster trick 20 years ago when I did mine, remember cussing at Mazda for not making the wires in the truck 6 inches longer, and got my arms all scratched up !! And a few weeks later I was back at the dealer so I asked them to look in another switch's bag, and that one also had no push nuts, and Mazda had no listing for those push nuts either. In case you were wondering: the Mazda factory service manual does NOT instruct to remove the cluster to help out either !

Just out of curiosity:
To get the cluster out, it helped to take the left dash vent out to clear the lower mounting tabs on the cluster. I decided to remove the center dash panel and for the life of me I couldn't figure out how to get the knob off of the stupid electrical ventilation switch (upper). Mine may be just particularly hard to get off, but does it just pull off like the lower switch, or is there a special trick to that one? I eventually gave up, and got the cluster out anyway.

As far as the ignition troubles I'm having, the problem was not solved by the new switch. I also have a new igniter handy, and that is the next thing to go in. The trouble is it dies while I am alone, and of course never in front of my garage where the tools are! To test things like spark while you are by yourself is pretty challenging in a parking lot (maybe ask a stranger to crank it).
Here is the issue:
Cold the truck starts fine most of the time. Driving around, I get random misfires and when it misfires the tach needle twitches and jumps up a few thousand RPM. It has never completely died on me while driving. If I park it for a few minutes (grocery store) and come out, it won't start. When this happens, I check with key on voltage to the ECU, fuel pump, and ignition system. All check out just fine. No blown fuses. The truck will turn over fine, but has no interest in starting. If I leave it and go get a coffee with the hood up for about 20 minutes to cool off, the truck will magically start again and run fine aside from the spontaneous misfires.
Here are the parts that have been replaced (most were due anyway for a tune up)
Ignition switch
Plugs, Cap, Rotor, ignition coil
The truck has an MSD that I bypassed to run the stock ignition and the problem persisted. It also has an MX-6 injection conversion. The igniter was my initial hunch, because the Ignition and the fuel injection both get their firing signal from the igniter. If the igniter fails, you get no fuel, and no spark because the ignition and ecu don't think anything is happening. I'll update after the install of the igniter to see if that solves the problem.

"Just out of curiosity:
To get the cluster out, it helped to take the left dash vent out to clear the lower mounting tabs on the cluster. I decided to remove the center dash panel and for the life of me I couldn't figure out how to get the knob off of the stupid electrical ventilation switch (upper). Mine may be just particularly hard to get off, but does it just pull off like the lower switch, or is there a special trick to that one? I eventually gave up, and got the cluster out anyway."

No, I did not remove the left vent or the center dash panel to get the instrument cluster out. I think I removed the top steering column cover then the four screws securing the cluster. Then I unclamped the speedometer cable from its clip, pushed the cable towards the rear of the truck, then pulled the cluster towards me, and reached my scrawny hand around the cluster to unfasten the speedometer cable and the electrical harnesses.

yeah, the speedo cable is probably the most challenging part of that job. It took me some thinking to go into the engine compartment and pop it out of it's clip on the fenderwell to get enough slack to pull the cluster forward. Truck seems OK so far. Idle is smoother, and it hasn't done anything weird to me during a test drive. I went into the parts store for a bit and came out, and it started fine. I hope it stays this way, because I don't really know where I would go from here if it keeps this up. Thanks for the help!

If something happens, just troubleshoot while it's "not working" like we all do !

Well, so far it looks like the new igniter took care of the problem. It was actually pretty new. It had 2013 stamped right on it, which means I may have replaced it when I did the engine rebuild and I forgot about it. The fueling is much smoother now on take off from a start, and I haven't had any hiccups, random tachometer needle jumps, or no-starts. I'll keep my fingers crossed, and my meter handy :-).