A couple questions, since I’m putting a 91 long-nose engine into a 90 short-nose car, and I didn’t disassemble either one.
The coil plug on the 91 engine doesn’t seem to match the harness on the 90. I don’t have the coils from the 91 to compare(I don’t think), so am I crazy or are these different.
Next, there’s this single wire connector next to the coil plug on the harness side, but I can’t find anything on the engine side to mate it to. Any ideas?
Bueller? Bueller? (Keith?)...
I went back out this morning & figured out the single wire connector attaches to the O2 sensor from the other side of the engine.
I stared at the coil harness plug for a bit before I remembered I still have the chassis this engine was pulled from behind the garage(duh). Crappy pic - I was fighting off mosquitos & keeping a spider who’s setup shop in the engine bay away - but the 91 definitely has a different plug(the one on the left). Hopefully the pinout is the same, since it looks like I’ll be cutting & splicing it in.
Next question: where does this bracket go, or does it even belong on a 90?
I don't have an answer on the plugs... I ditched all that when I did my VVT swap because I went with MS3. Sorry.
The bottom bracket looks like a transmission x-member... which a Miata doesn't have. I can't remember seeing anything that looks like that on my '92. Are you sure it came off a Miata?
I don't remember there being a different plug on the various 1.6 coils, but I'd have to go to the wiring diagrams to be sure.
About the coil plugs - just put the 1990 coils on the 1991 engine if the plugs don't match.
That bracket is not from a Miata as far as I can tell.
In reply to Keith Tanner :
Thanks Keith!
Unfortunately I don’t have the 90 coils, but I contacted the seller to see if they might be in a box somewhere we overlooked.
Good to know about the brace. I couldn’t find anyplace to attach it, but he’d previously parted an NA8 & I’ve found a couple of those pieces mixed in with the NA6 parts.
Next question: Which fuel line connects where?
It looks like the line from the rear of the intake(to the left in this pic) should connect to the front hard line(also to the left in this pic), while the line from the front of the intake should connect to the other hard line. I’m not sure which ones are pressure vs. return, does that sound correct?
One is feed, the other return. I can look when I get home from work to see which is which... don't want to give you bad info, and I can't recall off the top of my head.
Someone will probably post the answer before then anyway... 
The one attached to the FPR is the return line. On a 1.6, the front hard line goes to the rear of the rail.
In reply to Keith Tanner :
Awesome, thanks Keith!
Next question: what am I missing here?
It it looks like something used to be bolted down to that bracket & presumably the 8-pin plug connected to it?
According to my wiring diagram, that plug is for the ignitor.
In reply to Rodan :
Thanks! That makes sense, the wiring seems to match the coil harness.
I peeked under the tarp on the parts car & it still has an ignitor, so I’ll pull the tarp off later & steak it while I’m out there pulling the wheels off.
Electrical question this time. After installing the ignitor I decided to see if it would crank over. It does not. All I have are headlights - no starter, gauges, turn signals, or blower fan.
Im guessing I missed a ground somewhere. I remember connecting a positive cable & single spade connector to the starter, a positive battery cable & multi-pin connector to the alternator, several small ground wires to a bracket on the passenger side rear of the head, and one small ground wire that I wasn’t sure where it went I attached to the passenger side rear valve cover bolt. I don’t remember seeing any batter cable-sized grounds though?
Not sure if there is a "battery size cable" ground on any starter. Possible you've missed a battery size engine ground strap?
Whatever it is it's going to be simple I bet.
IIRC the only ground strap is on the driver's side. Goes from the bellhousing tin to the body.
Have you checked all the relays and fuses, both underhood and inside?
There's a really important ground strap on the PPF near the back.
It's hard to stop an early Miata from cranking. There's the clutch switch and the solenoid and the ignition switch. That's about it.
In reply to Keith Tanner :
Thanks Keith, I’ll check both switches.
Rodan:
I’m pretty sure I don’t have a grounding strap, but I’ll double check. Hell, I might just ground the engine straight to the battery w/ jumper cables to test it out.
Whoops... forgot the PPF ground strap, but I was thinking engine compartment.
The one that should be there bolts onto the engine at the bellhousing cover where the dipstick tube support bolts on, and to the chassis on the 'shelf' below the master cylinder/booster.
In reply to Rodan :
I double checked after dinner, the bolt is loosely threaded into the shelf, but the strap is missing & not on the parts car either. I’ll make a cable to replace it, though according to a few posts it shouldn’t prevent it from starting.
No genius here, but is there power from key to ignition, or starter? Power to coils, and fuel pump? Maybe the connectors need a look see. Multimeter time.
In reply to Dirtydog :
That’s my next step. I didn’t have any time to troubleshoot today, so I was hopeful it might be a known/easy oversight.
I've experienced that driver side ground strap preventing it from cranking. Try making a ground between the engine and body with jumper cables and see if it cranks.
In reply to EvanB :
Good to know!
I went out before work & actually found the ground strap was there. It was hiding behind the dipstick & intertwined with the O2 sensor wire, so I mistook it as a part of the same harness.
I was reading about the ground under the clutch & slave master cylinders too, and when I checked it this morning it looks very crusty. I’m going to clean it up too before I reinstall the battery & continue testing.
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