Tach not working after new transmission install

[machstang23]

I recently installed a new motor and tremec 3550 tansmission, and now my tach isn't working. What drives the tach? what did I forget to hook up that is causing my tach not to operate? I have made and double checked all my connections on the transmission, is there somethign under the hood I am forgetting? any advise would be greatly appreciated.

 

[5.0Droptop]

Sounds like you stripped the tach gear. That will cost you.

 

[5.0Droptop]

I was just playing. The tach signal is picked up from the neg coil wire. Did you add a MSD box or anything like that?

 

[machstang23]

no, I didn't add a MSD box, but I did convert the car to mass air using the engine harness out ouf an 89 (mine is an 88) and I was told that everything was compatible, is there something I am missing or maybe a bad fuseable link?

 

[5.0Droptop]

I cant say. When you go swapping a harness it could be anything.

 

[5.0Droptop]

machstang, I would email jrichker he has all kinds of knowledge on wiring etc. He can link you to diagrams etc.
http://forums.stangnet.com/member.php?find=lastposter&t=742016

 

[jrichker]

The Tach signal comes off the IDM output, pin 4 on the computer with a dark green/yellow wire...

Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel pump, alternator, ignition & A/C wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Computer, actuator & sensor wiring
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Fuse panel layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Vacuum routing
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

 

[5.0Droptop]

See I told you Jrichker is the man with the diagram!! Now you know where to start, Pin #4 at the plug, it appears to go to the TFI module plug to dizzy. It looks like it may have a resistor of some sort inline 5.9" from the main plug.