I did some fairly minor electrical work, but it managed to get stretched out well beyond my memory's capacity courtesy of the insane amount of rain thrust upon us this past month or so. I resoldered the CPU, diagnostic unit, and AC control, and finished the removal of a fuel pump cutoff setup. Aside from simply splicing together the two fuel pump wires, I don't know that any of it had anything to do with actual operation of the vehicle outside of the horn and lights. During the job I had the dash and most of the AC system completely out at one point with all the various plugs undone. Between the wire insulation hardening in position and Mazda's wonderfully matched/unique plugs, it was a breeze to get everything back in its place... I think.

I have it wrapped up to a point where I finally tried to start it last night. It turned over fine (starter works), but never really kicked. It sat for close to a month without running save that I tried to start it at some point in the middle to give the battery some power while I was messing with the sunroof.

I'm trying to figure out why it won't start. My first suspicion was the splicing of the fuel pump wires under the dash by the steering column. I did it with the majority of the dash in place (instead of while it was out), and the jackass that thought a fuel pump shutoff was a better idea than just replacing the injectors cut the wires pretty close to the plug, so it was pretty damn tight. I figured that was my first suspect. I went out there just now and tugged on the wires to make sure I didn't mess up the connector; solid. I got out the multimeter to make sure I didn't crimp into insulation somehow, and that checked out with a solid connection. Probably not the fuel pump wiring...

I looked around further and found a few plugs without homes. I'm pretty sure they didn't have homes in the first place and can't find anything nearby they might mate with, but thought I'd see if anyone knows off hand what they're for:

Under the DS dash by the fuse block and CPU:


What sort of options might have had a plug like that in '86? Did the turbo/NA cars share a physical harness? Was there an optional security system or something that would be connected here? Some turbo-related device?

Under the radio:


I have the super duper 9-band EQ jobby, and I imagine these probably have to do with other optional setups, but want to make sure. There are two light sockets that I believe are for the ash tray and the lighter, then there are the three others. Is there anything related to the radio that would make it so the car won't start? Maybe something connecting to the switches behind the shifter? Maybe I left one out of the radio and it's got some sort of backward security thing?

There's also a few spare plugs by the AC fan that I couldn't get to with a camera. Two are down in the corner associated with the harness and nothing else, the third is right off the fan. None have anything associated that I could locate, but I'm pretty sure there must be some option or another. Ideas on what those might be?

Given the manufacturing methodologies I've been able to discern from messing around with this thing, I'm pretty sure they're for options I don't have. I don't think I've messed with anything that would actually be tied to making the engine go though... I could be wrong. The wiring schematics are really difficult between the format and the poor quality scan, and my craptastic 6 year old computer that can't handle scrolling through large PDFs makes it even more difficult (it's extremely difficult to follow a fine line in a complicated image when it jumps instead of scrolls).

 

first plug, the big white one looks like maybe its for the power steering brain box?

the second ones by the shifter are for the ashtray/cigar lighter light, and the a/t PRNDSL if equipped.

the third by the blower, there is just this giant plug that goes nowhere, no idea what its for, one of the great mysteries of our time

 

I didn't know hydraulic power steering required any sort of computational power... My truck's PS certainly has nothing like that... 80s Mazda... Go figure.

Bingo. Exactly the sort of thing I was looking for here too!

I was pretty sure I remembered an orphan plug while I was pulling it apart, and I did absolutely nothing down in the corner with the harness, but my memory sucks if I'm trying to do something like that on the same day. For as dry as this place usually is (being the high desert and all), we've gotten more rain than we can really handle. Not just quantity, but consistency. It's taken me a solid month so far to get through what should have taken all of a weekend!

Meanwhile, it's nice to know that I didn't miss something silly, but the thing still won't start! Any chance there's some function in the CPU, diagnostic jobby, or AC that might prevent the engine from starting should it have a bad connection, short, or otherwise fail? The battery is pretty much dead (and probably starting to sulfate), and I can't turn the key and be under hood at the same time, so there's really not much I can do right now. I've only been under hood during the past month to dis/reconnect the battery, so first suspicions are dash related, but it's always possible something could have spontaneously failed at an inopportune time just to be as befuddling as possible.

 

some of the power steering cars (i think mainly GXLs) had computer controled power steering on top of the hydraulic system

 

the 1986 Rx7 has the worlds first variable assist power steering system, there is a stepper motor on the pump to vary the amount of pressure to the rack based on speed, and a couple of other parameters.

when you combine that with the GXL's automatic adjusting suspension, which varies the stiffness of the shocks based on, speed, rpm, steering angle, and brake pressure. plus the 6 port intake, dynamic rear steering you have the most technologically advanced car in the world until the BMW 7 series came out in 1988

 

Yea, I have the 86 GXL. Very advanced car for its time. Everything worked perfectly before I swapped it all out in the name of performance. Still not sure how I feel about the variable speed PS though. It is the one thing left intact of the whole deal. But that first big white plug in the first pic does appear to be the PS box. I had mine out a few times trouble shooting things.