drft_180sx

Not getting the slightest bit of spark....in other words the tach is not moving at all nor when the wires are pulled and placed near a ground is there a spark. I have checked the fuse under the hood ... and the fuse box under the dash (the engine fuse - 15A) looked fine.

So, here is what i'm thinking, 2 possibilities....

1. There was a white connector (black, black/white stripe, brown/yellow stripe, green/white stripe?) by the ECU that I couldn't find the other half to...it was connected to the engine side of the harness...and i'm not sure if it's a check connector or not? I assumed it was? I am really hoping that is the problem! lol.

2. The shortblock came out of a carb'd car. I had to adjust the CAS from the old engine onto this block...I read up how to "zero" out the CAS. Could there be some other thing i had to adjust to go back to EFI?

drft_180sx

sweet! hailers is on! i read up on a lot of your posts (but didnt understand anything) in the search for my answer! hopefully you'll stop by here!

drft_180sx

OK so ... after a little more searching the connector by the ECU was for the "Atomospheric Pressure Sensor" I connected that up..

so now what? still doesnt spark.. =[

RX7_Racer_84

Check your ground wires. I had a similiar problem. I couldnt get spark anywhere, the ground under the intake manifold was loose. Try that, I hope it helps.

Rey871

iTrader: (1)

Drift,

I am facing almost a similar issue. Hailers has been helping me out. Check https://www.rx7club.com/2nd-generation-specific-1986-1992-17/wtf-wrong-w-my-7-no-spark-coils-664149/. I really hope your spark comes back after some of the stuff that he lists.

Good luck.

Rey

drft_180sx

does anyone know where the ground by the computer is?

iceblue

If the main relay circuit is powered on and you do not have spark then you have either.

Bad signal from the CAS or dead ECU. The CAS has two ground a home and a trigger signal fed directly to the ecu the ECU then flips ground current to the injectors and low voltage signal to the coils to fire both items are hot all the time. Check the black wire with yellow stripe connected to brown wire on the coil for 12vdc with key ON. If you have 12VDC go to the cas try a spare one rotate the end and see if the injectors click while key is on. Narrow it down from here.

drft_180sx

UPDATE:

spinning the CAS by hand does NOT get the spark plugs going....does that mean i have a bad CAS or what else UPSTREAM can it be?

I swapped ECU's, so I think it's safe to say that isn't the problem. What are my other options here ppl?

drft_180sx

Thanks so much for the reply.... like i said, i tried a new ECU, no luck. I have a turbo CAS laying around somewhere, wonder if that is interchangeable with the non-turbo one?

iceblue

Yes the CAS between the models are identical. If you have a good CAS and ECU and power at the black with yellow stripe wire you have faulty wiring from the CAS to the ECU.

drft_180sx

UPDATE: so there is power at the black/yellow wire at the leading coil...

what to check next? i haven't found another CAS yet...

HAILERS

No spark? Check the ENGINE FUSE in the interior.

Or there is the yellow two scoket plug in the engine bay that's called the fuel pump check connector. Jumper the two sockets with a piece of wire and turn the key to ON. IF you hear the pump running in the fuel tank.............then the ENGINE FUSE is good and there's no need to look at it.

EDIT: Oppps. I just read all your post. You already checked the ENGINE fuse. Well, try the fuel pump check connector while your at it, as described above.

You just put this engine/harness in the car? The ECU's ground point is on the top of the REAR ROTOR HOUSING. Two black wires in a ring terminal. ECU won't spark unless those two wires are grounded.

OR, you might try this. Since you just installed the CAS and know how to do that, remove the cas but leave its plug attached to the harness. Key to ON. Spin the CAS bottom gear. Do you hear clicking when the cas bottom gear is rotated?????? Is the clicking coming from the sparkplugs or the fuel injectors. It would only be the PRIMAY fuel injectors so don't pay attention to the secondary injectors.

HAILERS

EDIT: Just read your last post. Found 12v at the black/yellow. Hmmm. Sounds like no ground for the ECU. No ground for the ECU results in no spark and no clicking of the fuel injectors when the cas is turned.

IF you have a digital meter, you might go to the boost/pressure sensor and pull its plug off. See if there is 5vdc on the BROWN/WHITE wire in that plug with the key to ON. Should be real close to 5vdc. If you see something like 2-3vdc.....BAD.

What your checking is the ECU's output of the ref voltage. No 5vdc ref voltage equals a dead ECU. Not likely but possible. Check that out.

JUST IN CASE: Grounding the ECU is NOT putting a ground wire to the ECU's chassis. The internals need grounding and that is done with the two black wires grounded on top of the REAR ROTOR HOUSING on a series four car. I'm guessing this is series four. I did not read everything.

drft_180sx

I am only getting what seems like .20V at the Brown/White Wire at the pressure sensor. So i am gonna go look for the two grounds on the rear rotor housing... I only see the one that attaches the firewall connector to the rear rotor housing.

I can't locate the other one? is it the one under the intake?

*THANKS HAILERS! it's really appreciated!

drft_180sx

SOOOO.... basically... i directly grounded the ECU with a wire from under the dash... (where the 2 black wires splice together) to the battery negative pole. Still when the CAS is turned by hand...i'm getting no spark or fuel clicking..


ANYONE HAVE ANY IDEAS? what to check for next? Bad CAS? Bad Main relay? Shoudl i check the fuses again? Perhaps replace them anyway...?

drft_180sx

OK SOO....Just so everyone doesn't have to read all those posts... I'll condense everything below:

- Black/Yellow wire by the leading coil pack has 12V.
- Brown/White wire by the pressure sensor gets only 0.11V ON TWO DIFFERENT ECU'S!!
- There is gas going to the rails.
- When CAS is turned by hand, there is NO spark and NO clicking of the primary injectors.
- ECU ground (two spliced black wires under dash) have been directly connected to a ground (negative pole of battery).

SOO... if anyone has a clue...help!@!!!??! Thanks

Jahan

PS. i'm going to go pick up a spare CAS and ECU from a parts car.. should i get anything else? main relay? etc?

drft_180sx

NO CLUES anyone? Imma miss rotorfest tomorrow.. :wtc:

HAILERS

You have 12v at the ECU?????

Small plug. Pins 3I and 3J on the far left of the small plug as you look into the wire side of the plug?

Ground on pin 3A on the far right of that plug? Black wire. Pin 3G?? Black wire same plug?

Gnd on pin 2R of the middle plug? Black wire.

CAS don't go bad unless you stick a screwdriver in it's guts.

No ref voltage coming out of the ECU means a fried ECU or no power going to the ECU or no grounds for the ECU on the wires mentioned.

The power comes to 3I on the MAIN RELAY. Main Relay does not pull in unless the ENGINE fuse is good.

I think for some reason your not getting any pwr to the pin3I on the small plug FROM the Main Relay.

The Main Relay has two plugs. If you pull the plug off that has four wires, you should have 12v on the Black/Green and the White/Blue. These are powered by the two EGI fuses in the engine bay fuse box.

IF you have pwr there at those two wires, then make two jumper wires and jumper b/t the Black/Green and the Black/Yellow and also b/t the White/Blue and the Black/White.

It seems the Main Relay and Engine fuse must be good because you said you got 12v on the black/Yellow wire at the Lead coil. So maybe your not getting pwr from the Main Relay to the ECU pin 3I???????

You SURE both EGI fuses in the engine bay fuse box are good?

drft_180sx

OK! First and foremost, THANKS A MILLION HAILERS!!

So... Both 3I and 3J are at 12V also, 3A, 3G and 2R have been confirmed to be good grounds. The wires have been jumpered. NO LUCK!

SO.. MY GUESS I NEED A THIRD ECU! unlikely, but seems like everything else is getting power... and grounds.

EDIT: Upon further thinking...can't it also be the coils, or the AFM? is there a signal coming from the AFM to sync the fuel injectors duty?

HAILERS

AFM is not used during start at all.

You say there is no spark and no clicking of the Primary fuel injectors when the cas bottom gear is spun by hand with the key to ON. So, no it's not a bad coil.

IF you had the key to ON when you checked the brown/white wire at the boost/pressure sensor, plug off, and you had no 5vdc, then there's something wrong with the ECU.

OR, Try this. Remove the plug from the boost/pressure sensor and ALSO from the AFM, then go check for that 5vdc on the brown/white wire at the boost/pressure sensor. IF it is there now, then the AFM is corrupt and is killing the ECU or 5vdc ref voltage signal from the ECU to the sensors.

While your there at the boost/pressure sensor, see if you meters good and or the gnd point for the meter is good, by going to the BLACK/WHite wire in that boost/pressure sensor and see if you see 12vdc on that black/white. IF you do, that's good. Means the ground poiint you found for the meter is good and when you looked at the brown/white wire earlier that that was the correct reading.

Really odd two ECU suddenly went bad.

What kind of work did you do on the car recently?

drft_180sx

HEY HAILERS!!! SooOO ... the brown/white wire is getting 5V when the AFM is not plugged in!! What does that mean?? start the car without the afm connected?

BTW PM me your address...i have this neat 2nd gen book by yamaguchi that is out of print! (its a extra copy) and if you don't already have it...its yours, for all the noobie help you've been giving me!

HAILERS

Just in case: You check for the 5vdc at the boost/pressue sensor NOT to see if the boost/pressure sensor is good/bad, but to see if the ECU is putting out the 5vdc to the various sensors. It uses that 5vdc internally to make the spark and fuel injector drivers work in the ECU. No 5vc ref voltage.........no start.

The CAS makes voltage itself when spun. IT does not recieve voltage from the ECU. It sends a a/c signal to the ECU and the ECU uses that signal to regulate spark and fuel injection.

AFM is NOT used for STARTING. The ECU has a START MAP all it's own that is used for fuel delivery based on rpm under 500, a Start signal on pin 3B when the key is HELD to Start, and a signal from the water thermo sensor.

Again, no 5vdc ref voltage on the brown/white wires equals a car that will never start. Might check the brown/white wire on the TPS connector while your there. Pull the plug off and check the brown/white on the harness side of the tps plug. Should be 5vdc.

I'd worry a bit about what might have grounded out the ref voltage signal and burnt up the ECU. It'd have to be something at one of the sensors that use the ref voltage. It'd have to be shorted to gnd.

BOOST SENSOR, AFM , TPS, ATP, VARIABLE RESISTOR are the ones that use that ref voltage.

drft_180sx

UPDATE: With the AFM disconnected the car will start for 1-2 seconds then die. Not sputter, but just shut off.

What to do next? new afm i guess?

HAILERS

Makes you wonder about the afm, yes. The car started because it uses the internal START MAP and does not use the afm for start.

Once the rpm got over five hundred, then the ECU uses the afm signal and it was disconnected so the car died. Plus the fuel pump won't keep running unless the switch inside the afm is made. No afm no fuel pump action. So? Was it the afm keeping it from starting or????

With the afm disconnected look for five volts at the brown/white boost sensor wire. If there, put the afm plug back on and see if it remains five volts dc on the brown/white wire. IF it drops down to way under two volts or so, then unplug the afm and see if the volts on the boost sensor brown/white come back to five volts.

Heck. If it'll start several times with the afm plug off, then put the afm plug back on and see what happens.

drft_180sx

Already did that! with the afm disconnected i get 5V, with it connected i get .10V at the brown/white wire by the pressure sensor.

Looks like its time for a new afm.


Wouldn't start...guessing the ECU 5V ref output gets messed up and the spark/fuel injectors don't come on.