240Z Tach Wiring After 123Ignition Install

[rcv]

47 minutes ago, Zed Head said:

Run an extra wire around the tach circuit, parallel circuit.  Use a potentiometer to tune the current flow

Yeah that's a good idea. You might need to put a very small resistor in parallel with the potentiometer, otherwise the current through the pot will be super low and subject to whatever the impedance is in just the wiring.  The goal would be to make the current flowing through the pot+tach the same as it used to be, but to also get some extra juice by pulling in extra current through the low-ohm resistor that's in parallel.  I'm not sure when I'll have time to source the parts and try this, but it sounds like good experiment.

[Firepower]

I’m running 123/Tune+ with a non-standard coil and no ballast resistor. This is on a ‘73 240Z. The tach works & exactly matches the 123App. I just jumpered over the ballast resistor (in effect). Actually I put both wires on one side of the ballast resistor as that was easy. I do not know if my tach is different from other earlier ones.  I think it’s the “current loop” type.

Richard (alienpoker on YouTube)

Edited March 2, 2021 by Firepower

[rcv]

1 hour ago, Firepower said:

I just jumpered over the ballast resistor (in effect)

Thanks Richard - I believe I tried that, but had no luck.  I'll give it a shot later and see if I can figure out what I screwed up. When you say you jumpered both wires, you mean the Black/White wire, and the Green/White wire right?

Also, thanks for the "240Z 123 Ignition Tune+ Install" video you did you Youtube, it was my main reference when I installed mine and it was a huge help.

[Firepower]

No problem.  I really liked the tuning capabilities of the 123ignition dizzy for the L6.  You can have a tame tune for when you feel calm and want decent milage and a more “spirited tune” that you load for carving canyons or sporting around.

You are correct, from memory I have the green/wht, black/white and red wire to the 123/tune+ all on one side of the ballast resistor. Nothing on the other side.  The other black/wht wire goes to the coil.  So yes, I connected Green/wht, one Black/wht and the Red together. Everything works as it should. 
Hope this helps.

 

Edited March 2, 2021 by Firepower
Added picture of dizzy wiring.

[rcv]

On 3/2/2021 at 1:34 PM, Firepower said:

I have the green/wht, black/white and red wire to the 123/tune+ all on one side of the ballast resistor. Nothing on the other side.  The other black/wht wire goes to the coil.  So yes, I connected Green/wht, one Black/wht and the Red together. Everything works as it should.

Wahoo it works! Thanks for the help @Firepower  

For anyone else who stumbles n this thread, here’s how I wired it up. I made a “Y” connector to connect the following wires:

- Green/White

- Red wire that goes to the distributor

- Black/White wire that gets 12V when your key is switched to “on”.

 

The other black/white wire (which does not read 12V when the key is in the “on” position) goes to the positive terminal of the coil.

 

 

[PrincePaul]

Hey Guy´s.

 

I´ve the exact same problem/behavior like the thread starter but with a 280z. So I should have the tach that works right away with the 123 dizzy, but it doesn´t.

Mine is MJ 78 so it comes with no ballast resistor and with transistor ignition unit from factory.

 

During the restoration I changed the stock coil to a red Bosch with no resistor and removed the stock ignition unit completely.

The 123 is hocked up iaw instructions, red to coil+, black to coil - and blue to ground.

Elec. Fuel injection is removed completely as well -> exchanged with Webers.

 

So the tach gets its sensing cable from the minus side of the coil via a resistor. Nothing else is connected in line with it anymore.

I´ve measured the stock resistor, it has a value which I can´t confirm because I can´t find the oem value anywhere to check it to, but at least it has continuity. 

 

At first I thought of a ground problem of the tach itself as I just had the dashboard hanging lose during testing phase but now that everything is bolted down and still shows a jumping needle and when you push the throttle it goes back to 0. I probed the tach and its ground connections/metal strap and also tach to dash - all grounded perfectly.

 

Coil + has nothing but the black/white wire and no capacitor as 123 says its build in anyway.

Coil - has the 123 dizzy black, the tach sense wire and my fuel safety relay sense wire connected.

 

 

If I remember right my tach also doesn´t have that magnetic field loop mentioned in the other thread. But maybe a ferromagnetic ring thingy around the sense wire like you have on some electronic devices might help?

 

 

Any ideas?

Thanks in advance.

 

To be honest I´ve no idea where to start. Probably jumping the stock resistor in the sensing line and see what happens or run a new wire directly from the coil to the tach. Maybe a connector issue ?!

Edited June 3, 2021 by PrincePaul

[SteveJ]

The resistor value is 2.2kOhms.

[PrincePaul]

29 minutes ago, SteveJ said:

The resistor value is 2.2kOhms.

Thanks I’ll check.

I also found in some other thread that someone installed a capacitor like on the generator or coil in the sense line to smooths out the signal or a diode.

There is easy access to the resistor I might try those but now that the dash is in its really hard to get to the back side of the tach. Especially cause the dash has a cover on it…

[Zed Head]

8 hours ago, PrincePaul said:

Coil + has nothing but the black/white wire and no capacitor as 123 says its build in anyway.

Coil - has the 123 dizzy black, the tach sense wire and my fuel safety relay sense wire connected.

By "tach sense" wire you mean the blue wire that heads back past the ignition module, right?

What is this "fuel safety relay", and how is it connected/wired?  That would be new to the system.  The tachometer seems sensitive to the signal on that wire.  You could disconnect it for a test and see what happens.

[PrincePaul]

46 minutes ago, Zed Head said:

By "tach sense" wire you mean the blue wire that heads back past the ignition module, right?

What is this "fuel safety relay", and how is it connected/wired?  That would be new to the system.  The tachometer seems sensitive to the signal on that wire.  You could disconnect it for a test and see what happens.

Yes the blue wire. That one basically goes only from coil minus to tach, nothing else.

 

that’s the diagram for the pump.

It basically shuts the pump off if you’ve an accident.

[Zed Head]

Is it an inertia switch?  It looks like it supplies power to the coil also.

Have you disconnected/unplugged the factory ignition module?  While you're down there you can also test continuity back to the coil negative.  It's a branched circuit, one to the ignition module, one to the tachometer, one to the ECU.

The condenser/capacitor on the blue wire is easy to setup.  That's what worked on mine, with a GM HEI module.  Any condenser from an alternator will work.  The wire to the capacitor goes the coil negative, the capacitor can be mounted on the ground point on the manifold, nearby.  It's a cheap quick test if you have one laying around.  Won't hurt anything.

[PrincePaul]

No it’s a relay that powers the pump when ignition is sensed via the coil negativ. It does not supply power to the coil. It goes to coil pickup 1 which is the negativ side.

 

yes the factory unit it all gone also factory ecu. Yeah I’ve the old one from the positiv side of the coil, which I could easily hook up to the negativ side. But I’ll also try removing the fuel safety relay wire just in case. 
 

so 4 possible solutions right now:

1. wire problem, but as it senses something I guess not the case maybe still ground problem. Should be easily checked by direct wiring or probing

2. negative effect from the fuel safety circuit

3. interference where a condenser might help

4. resistor value wrong

 

 

i might also try the factory coil which was installed on the car - maybe it requires a different ohm value. But as it’s on the negativ side i don’t know why the Tacho would be affected by that.