So I just rebuilt the engine on my s4 n/a convertible, and after putting it back in the car I am having a crank no spark issue. I highly suspect it is an issue with the wiring from the CAS to the ECU and here’s why:
I don’t have spark to any of the spark plugs but I know they are good because I tested them on another car and they worked great.
I have fuel pressure because one of the hoses squirted fuel when I was testing the fuel system so I tightened the clamp.
After I tried starting it the first time and it didn’t work I assumed it was flooded from me cranking the engine to build oil pressure beforehand, but when I took out the plugs and cranked it, there was no fuel vapor. So that means the injectors also aren’t working.
When I crank it over the tachometer doesn’t jump and also the tach would sometimes not work randomly back when the car was still being driven.
I used my multimeter to test if I have continuity from the CAS plug to the engine harness, which I did have on both Ne1 to Ne2 and G1 to G2, and the resistance was within the spec from the Haynes manual.
I read on here that the connector between the CAS and the engine harness can be finicky and some people just hardwire it so I did that.
Next up I used my multimeter to see if I have continuity from the CAS through the engine harness to the plug that connects to the front harness, which I also did for both the G coil and the Ne coil.
so then I went to the plug that goes into the ECU and the Ne coil/hall sensor had continuity but the G one (green & blue wire on CAS) did not have continuity.
Which means that for some reason in the past 10 months that my cars been sitting in my driveway on jack-stands, the wires for just the top Hall effect sensor and only the section that’s in the front harness has some sort of damage/issue/kink. I doubt it’s rodents because all the other wires under the dash look spotless.

So my question is: what do I do next? Tear out the dash and the entire front wiring harness?

Please tell me there’s some other connector or relay or fuse I’m missing so I don’t have to do that.

 

Your fuel injectors may need cleaning. They could be clogged from when everything dried out while it sat those 10 months. Not sure about your spark issue. What method did you use to verify there is no spark?

 

Okay so I was reading another thread and I realized I checked the wrong wires from the CAS to the ecu for continuity on the ecu plug.
Checked the correct ones and continuity is good from CAS all the way to ecu.

So I’m thinking it’s either a bad CAS or an ecu issue.

Is there a way to test if the CAS is sending a signal to the ecu? I tried doing it by testing for voltage spikes from each of the two sets of wires from the CAS in the ecu plug with my multimeter. But maybe that’s not the way to do it because I got no voltage readings.

 

Injectors should be good because I cleaned them out while diagnosing why my engine was misfiring before I rebuilt it. Although maybe they just got clogged again.

To test spark I just had someone crank the car while I had one of the leading spark plugs plugged into the wire and I held it to the engine block. I held it to the head of one of the bolts for the p/s bracket. I didn't have any of the other plugs connected at the time but I did check all 4 plugs last week the same way just one at a time.

The tach also still doesn’t bounce when I crank the engine.

 

Been chasing gremlins all day and still no luck. Crank but no spark and no fuel in engine.
Any help would be greatly appreciated as I only have the rest of today and tomorrow to work on her until next weekend.

Here’s a few more things that may be relevant:
-plugs are for sure good, tested on another car
-leading plug wires both have 8k ohms and trailing wires have 5k ohms
-leading coil measures .5 ohms and trailing coils both measure .7 ohms
-with key on both leading and trailing coils have 12v
-I checked all 4 coils and for spark with the above mentioned method and got nothing
-adjusted Hall effect Senor magnets inside CAS to be as close as possible without rubbing
-CAS wires have continuity through engine harness, front harness all the way to plug that goes into the ECU (about 160ohms)
-tachometer does not move at all when I crank the engine
-none of the injector wires in the 10pin plug that goes into the ECU from the engine harness have 12v (with key on)
-the injector circuit relay under the dash next to the steering column has 12v to the brown top left wire but 0v to the blue wire beneath it (with key on)
-took off the ECU ground under the intake manifold and cleaned both sides of ring terminal, both sides of bracket that hold up the dynamic chamber, the bottom and threads of the bolt that hold it to the rear housing, and the top of the rear housing threaded hole with some 80grit.
-EGI INJ fuse is good
-all the warning lights come on the clock bezel when u put the key to on
-the green ECU check connector next to the leading coil has 12v on the b/w wire
-when I unplug the 10pin connector form the ECU and check pin 3I in the connector I only get .5v with key on
-the br/w wire that goes to the pressure sensor is getting 1.4v with key on
-the b/w wire to pressure sensor gets 2.5v with key on
-and the br/r wire gets .9v but only when the connector is plugged in to the pressure sensor and I put the multimeter in form the back, if unplugged it gets 0v (with key on)
-and finally the g/y to the leading coil stays at 0v and does NOT go to 5v when I crank the engine over by hand (with key on)

my conclusion is that there is an issue with the ECU and I need a new one or I messed up the engine wiring harness somehow when I took it out of the car. This is likely because I did do a rats nest delete and cut off all the plugs that went to the rats nest solenoids on the engine harness and just covered them in electrical tape.

 

Please someone help

 

You cleaned them out or sent the off to be cleaned by someone like RC Fuel Injector? Sometimes they will stick closed after sitting a long period and could need to be sent off to be cleaned. There is a procedure in the FSM for checking that injectors aren't clogged. I think it involves removing them and the fuel rail as a unit and seeing that they do in fact spray fuel.

You can also put a timing light on the spark plug wire while cranking and the light should flash if you have spark. At least mine does.

 

I think you could have just diagnosed the root cause of you're problem. This has been a common problem over the years on here. Someone while rebuilding their engine decides to do a rats nest delete while they're in there and then their car won't start or run right when they get it back together. Best to do one thing at a time. Rebuild get it running then delete the rats nest which is unnecessary anyway. Here is a quote from this thread posted just a couple weeks ago.'88 N/A no start after emissions delete - RX7Club.com - Mazda RX7 Forum

Unfortunately, you made putting it back difficult because you went hardcore and cut all the plugs off.

I also think you may have went the wrong direction with the CAS. It shouldn't have went bad while just sitting. Also may be a bad idea to start screwing around inside it while trying to diagnose multiple problems. Since it sounds like you had access to another car you could have swapped the CAS and seen if it changed anything. Now you've made it not possible to easily do that since you cut the plug off and hardwired it. STOP CUTTING PLUGS AND CONNECTORS OFF. Check there is continuity through the connector. If so, leave it alone. I really don't what to suggest. Study the FSM section pertaining to the rat's nest, fuel injection system etc.. Maybe you cut something important.

 

I cleaned the injectors out myself by hooking them to 12v with some leads and then spraying carb cleaner through them with a rubber hose to seal it.
That was awhile ago tho atp so they might’ve just clogged over time like you said.

I actually did also use a timing light yesterday to check just one of the wires and I got no flashes, the timing light was on thought bc the light in the side was on.

 

yeah I think what I’m gonna do is take the engine harness back out and then study the FSM wiring diagram and make sure everything that I need is connected.

here’s the things I cut off and taped each wire end individually with e-tape:
-all 4 colored rats nest solenoid plugs
-split air solenoid plug
​​​​​​-port air solenoid plug (both for ACV which I deleted)
-sub zero start assist plug

these I don’t have connected to anything but are still attached to the harness:
-green BAC connector
-intake air temp sensor (sensor prongs broke off, I’m pretty sure I don’t need this one as I did some research and ppl were saying it’s only needed for the BAC, which I deleted)
-air bypass solenoid valve connector (deleted this solenoid bc it also is only needed for BAC)
​​​​​​-cruise control connector (deleted cruise control because I never use it anyway)

here are the other sensors/wires that aren’t hooked up currently:
-oil temp switch in oil pan (broke off prong and again my research told me it was only needed for the sub zero start system)
-temp sensor on bottom of radiator (I stripped the threads, and research told me I only needed it for the fast idle which I also already deleted)
-a/c plug on driver side harness (deleted a/c)
-single wire next to coolant filler neck (research told me it never was connected to anything in my car if I don’t have a filler neck with sensor)

other things I deleted:
-front dashpot (was broken anyway and I wanted flames)
-fast idle lobe (I jus let my car warm up to operating temp every time anyway)
-wax sensor and double throttle plates (so that throttle is smoother and less restrictive)
-BAC since I took out the a/c anyway
-air pump (adds tiny amount of load)
-5th & 6th port vacuum actuators (will be converting them to be electronically actuated with solenoids and rom switch in the future, for now they are wired shut)
-ACV
-EGR
-OMP
-sub zero start
-charcoal canister (I put catch can in its place)

okay I’m pretty sure that’s everything, I might’ve mentioned some things twice but oh well

basically my question now is: do any of these things that I in plugged or cut off need to be plugged in to complete a circuit? Because that could explain why my ECU is not getting power. Maybe I don’t have to put anything back if I could just figure out which circuit I broke.

now to your second paragraph:
I the only reason I started with the CAS is because even thought it should go bad just sitting, I remembered that while the car was still driving the tach would randomly not work. Also when I looked inside the CAS the first time I found the broken remains of the little plastic plug that goes into the viewing hole. That’s why I thought the spinning things could’ve gotten messed up. I don’t think I’ve done any damage inside the CAS as it still spins like normal.
the other car I had access to was just a Mazda 3 junk car that happened to have working coil packs, I don’t have another rx7. I just cut the plug and hardwired it because at that point I didn’t know there was a connector between the engine and front harness yet. And I read on a forum here that rotaryevolution tends to just hardwire his CAS’s. I did check each coil in the CAS before I hardwired it and they were both good. Also doesn’t matter that much anymore because now when I check the CAS continuity at the ECU plug (the correct colored wires this time) they are both good.

I really appreciate you’re help so far though

 

Okay I feel really stupid now…

I have spark and fuel now.

when I was removing the engine harness I realized I never plugged one of the 5 plugs on the interior side of the firewall. It must’ve gotten stuck under the dash and I never saw it, so the whole past two days of chasing electrical gremlins, it was just one plug

 

Does your car run/idle okay?

You really went scorched earth on what you removed....

 

I got to start and it idled for about 10mins Monday night, after that I realized I didn’t put enough coolant in for my new koyorad so I got scared it would overheat and shut it off. I had to call it a night after that. I won’t be able to work on it again till Saturday.

It seemed to idle a bit rough, I initially gave it some gas so it could idle around 2k and after a bit it stayed at 2k by itself. When I revved it slightly it sputtered and dropped rpms and then went back to 2k. I’m assuming it just needs to break in the seals a bit and I probably need to adjust the throttle body and timing a little bit. It might also have a vacuum leak from me deleting all those things, although I’m pretty sure I capped everything off.