280zx distributor upgrade in 280z, tach now doesn't work

[Ownallday]

Where is the resistor located for the 78 280z Tach? I don't have my voltmeter to check at this time but would like to see if bypassing it does anything if possible

[Zed Head]

It's a bulge in that taped up wiring harness somewhere in or around your picture.  Find the bulge, peel the tape back, it's an odd looking plastic thing with two bullet connectors, small than a quarter.

Signs still point to the ZX E12-80/match box.  Nothing bad about learning more about where all the parts are though.  You've also confirmed that the ignition system will work even though the old ignition module is still plugged in.  I've wondered about that in the past.

[SteveJ]

23 minutes ago, Ownallday said:

Where is the resistor located for the 78 280z Tach? I don't have my voltmeter to check at this time but would like to see if bypassing it does anything if possible

Don't bypass it. It is there for a reason.

[Ownallday]

39 minutes ago, Zed Head said:

It's a bulge in that taped up wiring harness somewhere in or around your picture.  Find the bulge, peel the tape back, it's an odd looking plastic thing with two bullet connectors, small than a quarter.

Signs still point to the ZX E12-80/match box.  Nothing bad about learning more about where all the parts are though.  You've also confirmed that the ignition system will work even though the old ignition module is still plugged in.  I've wondered about that in the past.

Okay, I will search for it so I can at least test when I get my voltmeter. At this point it seems most likely the E12-80 box like you said, Exactly, had my car for 2 years still don't know all the in's and outs.

25 minutes ago, SteveJ said:

Don't bypass it. It is there for a reason.

Okay, I will wait till Tuesday when I get my voltmeter to test it.

[SteveJ]

Just remember to unplug the TIU when using the ZX distributor. Years ago a friend was trying to diagnose a customer's car with a setup similar to yours (triples and ZX distributor). It just wouldn't run right. I asked if he unplugged the TIU. Nope, the TIU was plugged in still. Once unplugged, the car ran like it should.

If the resistor is bad, you'll want a 2.2kOhm 1 watt resistor to replace it.

It wouldn't hurt to get a multimeter with a tachometer function to see the signal you are getting for the tachometer gauge. That could keep you from throwing parts at the problem.

[EuroDat]

If you pull the plug on the origjnal TIU and the tacho still jumps around unchanged, my bet is a faulty (matchbox) TIU on the distributor.

You could still check the resistor tobe sure. Like zed head said, it's under the passenger side dash section, taped into the harness.

[Zed Head]

If you have a spare alternator condenser/capacitor around you could connect it to the coil negative post.  I don't know exactly why (my logic is not of the professional sort) but it worked for me.  Won't hurt anything.

[Ownallday]

38 minutes ago, SteveJ said:

Just remember to unplug the TIU when using the ZX distributor. Years ago a friend was trying to diagnose a customer's car with a setup similar to yours (triples and ZX distributor). It just wouldn't run right. I asked if he unplugged the TIU. Nope, the TIU was plugged in still. Once unplugged, the car ran like it should.

If the resistor is bad, you'll want a 2.2kOhm 1 watt resistor to replace it.

It wouldn't hurt to get a multimeter with a tachometer function to see the signal you are getting for the tachometer gauge. That could keep you from throwing parts at the problem.

Yes I have mine unplugged for the meantime. Made no difference with it plugged though. Tuesday I will test it all out.

 

37 minutes ago, EuroDat said:

If you pull the plug on the origjnal TIU and the tacho still jumps around unchanged, my bet is a faulty (matchbox) TIU on the distributor.

You could still check the resistor tobe sure. Like zed head said, it's under the passenger side dash section, taped into the harness.

This is somewhat what I am leaning to also. I will test resistor on Tuesday once I get my voltmeter but my guess is the resistor is fine

 

33 minutes ago, Zed Head said:

If you have a spare alternator condenser/capacitor around you could connect it to the coil negative post.  I don't know exactly why (my logic is not of the professional sort) but it worked for me.  Won't hurt anything.

Is this the condenser you are talking about, it's the only one I have? Funny thing as its not connected to the coil at all.

 

Something I just noticed is my two old positive and negative coil wires are just sitting hanging out of the wiring harness. Could this have anything to do with the Tach not working on low rpms as the guide doesn't exactly mention anything about using the old coil wires and not sure it makes a difference since I switched to Triples.

Edited December 6, 2020 by Ownallday

[Zed Head]

40 minutes ago, Ownallday said:

Is this the condenser you are talking about, it's the only one I have? Funny thing as its not connected to the coil at all.

Something I just noticed is my two old positive and negative coil wires are just sitting hanging out of the wiring harness. Could this have anything to do with the Tach not working on low rpms as the guide doesn't exactly mention anything about using the old coil wires and not sure it makes a difference since I switched to Triples.

No, I'm talking about a new condenser that wasn't part of the original setup.

Edit - actually your engine wouldn't run if the blue wire was not connected.  So, ignore the words below.

The blue wire needs to be connected to the coil negative terminal.  That might explain both why the tach doesn't work and why the ignition system worked with the old module plugged in.  Not really clear what you mean by "coil wires" though.  What are you using to power the ZX distributor?  

Edited December 6, 2020 by Zed Head

[Zed Head]

https://www.atlanticz.ca/zclub/techtips/distributor/index.html

Edited December 6, 2020 by Zed Head

[Ownallday]

9 minutes ago, Zed Head said:

No, I'm talking about a new condenser that wasn't part of the original setup.

The blue wire needs to be connected to the coil negative terminal.  That might explain both why the tach doesn't work and why the ignition system worked with the old module plugged in.  Not really clear what you mean by "coil wires" though.  What are you using to power the ZX distributor?  

Oh okay, I see. I don't have any spare condensers then.

Right side of the coil is negative with the blue wire connected for the tach and the black wiring going to the dizzy. On the left side of the coil the positive side has the white wire going to the dizzy and a black/white wire which was originally connected to the old coil going into the wiring harness. These are the only wires currently setup to the coil

The two wires I am talking about that I have hanging were originally in this spot. They are going into the wiring harness.

[Zed Head]

Those wires, the red and green, actually went to the old distributor and the ignition module under the dash.  They are the trigger wires.  Not used anymore because all of that is contained in the ZX distributor now.

If the engine starts and runs properly and the tach needle is twitching then odds are the connections are correct.  The blue wire supplies both the ECU and the tach with the spark signal, to fire the injectors and run the tach.  They're on the same wire.

Might also be that your new coil is "noisy".  Might be worthwhile to swap the old coil back in, just to see.  The coil is the other thing that is different now.