MillerLite

1987.5 N/A SE

I was doing my grounds and such last night and now my leading coil (the one in front) is not getting positive signal through the green and yellow with orange spotted wire. the negative is fine though. i tried chasing the green wire but its tough (anyone know where it goes?).
what i did last night:
-grounded from battery to leading coil bracket bolt to body.
-grounded black wire with open black connectored end to body (i assumed this was a ground and it goes into the leading coil... i could be wrong and this could be a problem)
-grounded to rear main coil bracket from strut tower
-grounded pressure sensor in engine bay and pressure sensor near ECU.... (((there is a problem here... i misunderstood some instructions from this forum and assumed that the four wires harnessing to that pressure sensor (:which doesnt have a vacuum hose connected anyways were all grounds. one of them is the ECU ground though im quite sure.. but there was also a green and yellow stripe one (different wire but same color from leading coil) on the harness.. i dont know if that pertains but its for informations sake.. I connected all four of those wires and grounded them. my engine would not start.. it just turned over. i disconnected them and put it back to harness how it was and it started.. at this point i dont know if the leading coil was not firing yet, i found out this morning. could this have fried the ECU? Are there any fuses i should check?? I just dont know)))
-grounded engine from strut tower to intake manifold bolt.

PS DOES ANYONE KNOW if the signal from the main coil (the one in back) is the same as the leading (the one in front)?!?!?! because i would just run this wire to both the coils and there would be no problem.. i just dont know if in a rotor the first and second plug fire at the same time... if i dont get replies with info im eventually going to get desperate and do this anyhow... plz have input

P.S. this morning i also found a relay with fucked up burnt out wires. i dont know what it is for. there are 4 wires to it, it goes to the side of the engine bay wall all the way in the front on the pass. side in that open area. the reay is white/grey. one of the wires is red. i think another is brown. and one is black w/stripe.. i patched it up though, anyone know what this is as well?

Icemark

The coils work by a switched negitive signal, not a switched 12volt.

At the leading coil, you have a Black/Yellow that is ignition, and a Green/yellow that is a switched ground. Both those feed into the ignitor/coil assembly.

The trailing coils have a again, a Black/yellow (ignition) and a yellow/blue (coil output for tach), a blue/yellow, and blue/red that are the coil's negitive trigger/ground/fire wires from the ECU and a Brown/Yellow that is a control wire.

HAILERS

Hi there! You've successfully destroyed the reference voltage output of the ECU. The engine will never start again until what you've done to the atmospheric pressure sensor has been undone and a new/rebuilt ECU is installed.

WAYNE88N/A

Somebody needs to take that damn "grounding how-to" off of this forum before any more cars get fried...

Ya think???

HAILERS

I came REAL close to giving an opinion on that Grounding How To, while writing the above, but I figured one Unusually Cruel post a day will do. humor

WAYNE88N/A

I must not count, then...You're cruel to me at least 4 times a day...I'll admit, sometimes I bring it on myself, though

This makes about 4 cars that I know off that have been killed because of that boost sensor grounding crap...

Oh well, the wife and kids don't listen, why should you guys, lol...

HAILERS

**************Oh well, the wife and kids don't listen**************************

Smart young lass you got there. Pay attention when she talks! humor

MillerLite

the engine starts and runs, rich at first but clears up. probably because the ECU reset with the battery disconnected and such.
what have i done to the atmospheric pressure sensor? ive hooked nothing up to that.
if i need a new ECU, where would i be looking at this at the cheapest and how much is it going to run me.
there has to be another scenario that could have happened.

MillerLite

can i jump the wire from the trailing coil to the leading coil?
does the spark from both plugs happen at the same time?
etc etc any info helps please
thank you

WAYNE88N/A

You won't listen to me, but if you want help, here goes:

Remove ALL of the non-OEM grounding wires you just installed...

Locate and clean up the OEM grounds (make good metal to metal contact from the ring terminals to the chassis and engine metal). The rear rotor housing ground, the tranny to firewall jumper, the gang ground under the trailing coil assy, and the main ground down by the starter are good places to start...

Marcus_F

No, the leadings and trailing don't fire at the same time. If they did, the car wouldn't need a trailing ignitor. If you grounded the single black wire that comes from the ignitor (it's loose, and just sits there), then the leading ignitor is fried. The good news is, used ignitors are cheap.

You may wish to consider undoing your additional grounding before proceeding.

MillerLite

the grounds will be disconnected and repaired.
i will get a new ignitor ASAP. i will try to find another ECU.

is the atmospheric pressure sensor fried? or just disconnect it and it will work?

and somebody, for the sake of our cars, please, please, PLEASE, PLEASE TAKE DOWN THAT DAMN THREAD OR FIX IT!

any other help will be greatly appreciated
thanks

WAYNE88N/A

Check out your ECU before you get another one, hopefully Hailers is wrong for once about you frying it...

Check out the 5vref output, and once she's started, all of the other 5v sensors, particularly the boost sensor's input...

https://www.rx7club.com/showthread.p...leshooting+ECU

Icemark

what thread?? provide a link

and why anyone would mindlessly follow a thread without personally confirming everything with both the FSM and their own tests is beyond me

HAILERS

Here's the deal. I MIGHT be wrong. Yes, hard to believe. But what you NEED to do is get a DIGITAL meter out. For ease of access, go to your BOOST/PRESSURE sensor. Pull the electrical plug off. Turn the key to ON (not start but ON). Check the voltage on the BROWN/WHITE wire. It should be 4.5 to 5vdc.

If it is, then I'M WRONG. If it's something on the order of 1-2vdc, I'm RIGHT.

There is probably NOTHING wrong with your ignitor/coil assy.

The ECU has a voltage regulator that puts out a reference voltage of approx 5vdc. If this is not being made, then you won't get an output from the ECU to the ignitor to trigger the ignitor. IF anyone is in doubt, then go right out and ground any of the Brown/White wires at any sensor and try to start your car. Ain't a gonna happen. ECU be fried like fried chicken.

Several sensors get the 5vdc reference voltage. I picked the boost sensor because it's easy to access. Others are afm, tps, atp blah, blah, blah.

Grounding a brown/white wire is much like cutting your dick off. Hard to repair.

I MIGHT be TOTALLY wrong. If so, disregard this post. Not likely though.

WAYNE88N/A

The "Grounding how to" in the archives...

These poor guys just getting started with their cars think that installing ground wires all over the place is gonna add 20 horses, and then hop on the forum (or PM me) and wonder why the car doesn't run right now...

sleejay

grounding howto:
insert knife in neck

come on people, dont blindly follow every write-up and tutorial you see on the intarnet... usually they have the basic points correct, but not the finer points.

PRINT YOUR DAMN FSM or BUY ONE... then you can read it, and learn from it, and know how everything works and what you can and cannot do.

Icemark

Ahhh thats why, the grounding how too only matches wire colors to some years and models.

It is correct for some models, just not all.

That is why a digital multi-meter and a FSM should be required for every owner attempting any electrical modification.

WAYNE88N/A

According to what I've heard here, it is only correct for the VERY EARLY '86 cars, which precludes 95% of our cars...

You're a mod- how about AT LEAST inserting a disclaimer into that thread stating as much...

Absolutely ZERO new ground wires need to be added to our cars...

Icemark

show me the link and I will put in a disclaimer... I don't even see it in the archive

WAYNE88N/A

https://www.rx7club.com/2nd-gen-archive-72/grounding-how-thorough-discriptive-199558/

Icemark

ah mah, it already says that the wire can change colors based on years... how much more does it need???

And it already says you should test the wire with a multimeter...

Don't know how much more of a disclamer these things need. Only a idiot would attach the wires without testing them first

WAYNE88N/A

You're missing the big picture here- it's not about wire colors changing...It's about the fact that the boost sensor cannot be grounded at ANY wire on every 86 1/2 and later, because it displaces the ground potential from the rear rotor housing for all of the 5v sensors...

Worst case scenario, the car runs like ****, because the ECU keeps getting two different potentials (and therefore two different voltage inputs) from the sensors. You can duplicate the same effect by bonding the alternator body directly to the chassis while leaving the rear rotor housing installed...

Icemark

Ah, yes, I see what you are sayin' about the boost sensor and confirmed it in the 87 and 88 FSM... okay I removed that section.

WAYNE88N/A

All right, man, we just saved future rookies a lot of wiring headaches