All of you with 89-93 HELMs Manuals for mustangs!

[asp84]

Just curious,
Its a fact that you hook up the White/Purple to a "crank" only source.........along with the Red and Light blue. Although if you check the diagrams for the 60 pin connector (EEC-IV Module Connector Pin Usage chart) , there is no indication of a White/Purple wire that goes in to the EEC-IV computer. Also under the definitions for the 60 pin connections for the computer there is no such input for a " crank only" source.
Anyway, My Question is, Where does this White and Purple wire go to???? WHat does it connect to. (So far, I have only heard the theory of, "it tells the computer that you are cranking, and gives it a different set of commands for starting) This sounds great, but there is no crank only wire that goes to the computer.
Anyway, can somebody with a Helms manual trace where this wire goes? Personally,

 

[Guy Groves]

The white/purple wire does not go to the EEC unit. white/purple (circut #26) goes to the HEGO (O2) sensors to provide heating power on the start condition to the O2 sensors.

The Red/LightBlue (circut #32) provides power on start for the TFI module on the distributor (<93 model 5.0). It does not go the the EEC module either.

The EEC IV does not get power on crank only. The EEC module needs power on start & run. This is the Red/LightGreen wire which is controlled by the ignition switch (source) and provides power to the EEC module pin#1, the E-Coil, and the TFI module (circut #16).

Hope this helps
Guy