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Stock Tach Not Working...

  • Thread starter Thread starter KDK1988GT
  • Start date Start date Sep 16, 2011

KDK1988GT

Founding Member
Jan 7, 2002
1,937
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37
Fredericton
Sep 16, 2011
#1
  • Sep 16, 2011
  • #1
Last winter I picked up a brand new painless wiring harness for my car, It has a wire for a tach hook up and when I've hooked this wire up to three locations that I figured would be the correct spot to hook it to. When I do this the car will not start it just cranks over and over..

- I've tapped this wire to my MSD tach out and no luck car will just crank over but nothing else.
- to my coil + side same results
- to my coil - side same results

I have my monster tach hooked to my MSD box and it works fine, but I would like to get the stock tach working again so when I data log I can log my RPM.

Any thoughts on this? Thanks!
 

jrichker

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Sep 16, 2011
#2
  • Sep 16, 2011
  • #2
The stock tach connects to the IDM circuit on the computer, computer wiring connector pin #4, dark green/yellow wire. There is a 22K resistor in the circuit and the tach connects to the computer side of the wiring and not the TFI module side.

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 Mustang FAQ - Wiring & Engine Info Everyone should bookmark this site.

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

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

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

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

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KDK1988GT

Founding Member
Jan 7, 2002
1,937
0
37
Fredericton
Sep 16, 2011
#3
  • Sep 16, 2011
  • #3
so what i'm getting out of that is that I should be tapping into the dark green/ yellow wire on the computer side of the wiring??

Thanks again..
 
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