Engine won't fire when tach wire hooked to coil

[70chall440]

Has this car run since you have owned it with the wiring hooked up? Something is definitely grounding out or is shorted (same thing). I ask this because if it was running with the grey wire hooked up and the tach worked, and now after reinstalling the rebuild engine, something occurred during the installation (such as hooking the wire to the wrong place and shorting it), if it has never worked as far you know (like you bought a non-running car), then the cause could be the same, but it would require tracing the wire all the way to the tach and going through it all methodically until you figure out what is happening; although this is probably what you will have to do anyway.

[usraptor]

No the car was not running when I bought it so I don't know if the tach was working?   

[70chall440]

Ok, well then it is going to probably require a full investigation. Do you have a power probe? If so, you can check to see if the grey wire is grounding out. If you don't have one, there are a number of ways to check, but I would HIGHLY recommend getting one, probably one of the best tools you can own if you are into Mopars.

Given what you have described, I would make the assumption that the wire is grounded somewhere or perhaps more likely the tach is burned out and shorting. Hard to say without getting in there and testing the wiring.

[Cuda Cody]

Here's a 1970 Challenger wiring diagram if it helps?   

[Cuda Cody]

On the back of the Tach, is there 2 washers like this?

Okay, here's some pics of the back of my dash wiring at the tach before it was installed in the car.  The pictures make it look like there is a cardboard washer on the white/red tracer wire but it's not there now??  Do you think that is my problem?

[usraptor]

Thanks Cody.  Any suggestions regarding the missing cardboard washer.  I assume a rubber washer would work to insulate the connection.  Your thoughts.

[usraptor]

On the back of the Tach, is there 2 washers like this?

Okay, here's some pics of the back of my dash wiring at the tach before it was installed in the car.  The pictures make it look like there is a cardboard washer on the white/red tracer wire but it's not there now??  Do you think that is my problem?

No I'm missing the one that the white/red wire connects to.

[Cuda Cody]

When you say "white / Red" I think I'm seeing "Grey / Red".  Right?  It's the one with the spade connector next to the Blue wire?  If it's missing the washer, then that might be your problem.  They are called "Red Fiber Insulating" washers.  They are all over and cheap.  I don't know the exact size, but you can find all different sizes on ebay.  Here's a sample (probably not the right size, just an example)...  [ebay]290642178098[/ebay]

On the back of the Tach, is there 2 washers like this?

Okay, here's some pics of the back of my dash wiring at the tach before it was installed in the car.  The pictures make it look like there is a cardboard washer on the white/red tracer wire but it's not there now??  Do you think that is my problem?

No I'm missing the one that the white/red wire connects to.

[usraptor]

It may well be grey with a red tracer but under the dash with a flashlight it looked white.  Anyway, thanks for the link.  I was searching in vain because I didn't have the correct name.  I'll order some tonight and hopefully you are right that that is the issue.  I'll report back when I get the engine re-installed and running again. Thanks again.  I really appreciate your patience and help with all my recent issues with this restoration.   Hopefully, things will go smoother from this point on.

[Cuda Cody]

Make sure yu double check the size.  I just put the link up to show you the name.  You'll need to find the right size.   

I'll order some tonight and hopefully you are right that that is the issue.

[usraptor]

I did.  Thanks

[anlauto]

 

Here's a 1970 Challenger wiring diagram if it helps?   

[usraptor]

While going through a jar of misc nuts, washers and bolts I found the missing fiber washer.  Installed it on the back of the tach and reconnected all the tach wiring.  Unfortunately, I can try and fire the engine yet so it will be a while to determine if this solves the problem.  Keep your fingers crossed.

[MOPAR FANATIC]

just read the whole thread,good luck,hope that's the problem     

[usraptor]

Thanks me too.  Unfortunately, the car is at the body shop for final paint work so I haven't had a chance to test it yet.