Question the first: Do I need a physical ground on the trailing coil in order for the tach to work? I have attached the wire from my trailing second gen coil to my first gen tach, but it will not seem to respond. The coil is firing fine, it's only the tach that won't work.

Question deux: When I lengthen the wire to my O2 sensor (because the header moves it further from the engine), is there a specific way to do this? Meaning, do I just crimp on copper wire or do I have to solder in the low voltage wire? Also, where can I get that low voltage wire like the stuff that comes on O2 sensors?

Thanks guys.

 

1: No

2: huh? low voltage wire?????

 

1. What could my problem be with the tach then? I'm sure it's the correct wire. It only needs to come off the coil to the tach right? There's nothing else to do?

2. The wire on O2 sensors is that not-copper kind (I think it's steel, but could be wrong). It has the actual wire wrapped in another metal that serves as a shield to eliminate the wire grounding at all before the signal reaches the ECU. This wire, I was under the impression at least, is called low voltage wire because it is a very low voltage moving through it and therefore it needs to remain very constant.

How about I change the question: How exactly do I go about extending the wire from my O2 sensor?

 

The tach also needs to recieve power. Sure you've figured that out though What kind of tach are you using?

You an use any old wire for the 02 sensor.

 

I'm using the stock 84 tach. You're sure I've figured that out, huh? Well, looks like your wrong! Hehe, I'll go check that right now. Where does the power come in at? N/M, I'm sure it's in the wiring diagram. BRB

 

Okay, I just went and looked at it. I have no idea where the power comes in. The only possibility I saw (assuming that it is one of the wires in the circular plugs) is the wire labeled "GEN" in the wiring diagram. I don't know what this would do otherwise.

So the power doesn't come from the trailing coil huh? I was under the impression that it put out a varying voltage signal. I guess not though.

 

signal comes from the coil neg. power and ground still have to be hooked up for the tach to operate.

 

but there is only one wire that hooks up to the coil?? wtf my tach just stopped working when i put in my msd direct fire?? could i have switched the wires that hook up to the igniter?? which one is it the blue one or black one??

 

But where does the tach get power from? What wire is it that plugs in to the back of the gauges giving it power?

 

I cannot figure out this damn tach. I've tried everything I can think of, even hooking up power to wires that I don't think should be getting power. No luck. Can someone please shed a light on this, I'm at the end of my (short) rope?

 

For an '84, the tach gets it's 12v from the ig pin on the connector shown (it's the wire side of the connection). According to the diagram, it is the only 3 pin connector on the combination meter. The same pin goes to the voltmeter and idiot lights, so if they work, the tach has power. Unless there is a bad solder joint at the tach itself.

-John.

 

Thank you so much, that's exactly what I needed to hear. I'm going to go try it right now. I'll let you know how it turns out.

 

Sweet!!!

It works. Good to know since I was apparently idling at about 2200 rpm!!! Anyway, that's the last major barrier in getting my project on the road. Thanks to everyone who responded to this, wouldn't have figured it out otherwise.

For the record, I had hooked that wire into my ignition switch, but had used a fried fuse when I wired it into my fusebox. Once I found out that it was definitely supposed to be that way though, I traced the whole thing and found the faulty fuse.

Good to know that I can uninstall/install my gauge cluster in under 4 minutes (which includes taking off the steering wheel and turn signals).

Phew, thanks again.