PLEASE all Electrical Experts NEED HELP!!!!

[PKRWUD]

What a pain in the arse.

Okay, forget that last part for now.

I've done some research, and it seems like your wiring is more like a '91 F-150 than a Mustang. Anyway, let's start at your first post:

At the Fuel Pump Relay w/ KOEO
Green w/ Yellow Wire 0V
Pink w/ Black Wire 12.4V
Red 3.63V
Blue w/Orange 0V

It should be like this:

At fuel pump relay with the key OFF:
P/B wire = Battery voltage (whatever the voltage is across the battery terminals, ie: 12.4v)
All other wires = Zero volts

At fuel pump relay with the key ON, engine OFF (for two seconds after key is turned on):
P/B wire = Battery voltage
G/Y wire = Battery voltage (zero volts after two seconds)
R wire = Battery voltage
B/O wire = Zero volts

At the EEC Power Relay
2 Yellow Wires at one terminal 0V
2 Red Wires at one terminal 4.14V
1 Orange w/ Green 11.6V
Black w/ White 0V

It should be like this:

At the EEC Power Relay with the key OFF:
Y wires = Battery voltage
All other wires = Zero volts

At the EEC Power Relay with the key ON, engine OFF:
Y wires = Battery voltage
R wires = Battery voltage
O/G wire = Battery voltage
B/W wire = Zero volts

BTW, these readings are all with the specific relay plugged in.

Solution:
One of the Yellow wires at the EEC relay connects to the starter relay's battery post by way of a Blue 20 amp fusible link. The other Yellow wire supplies this power to the ECM. Without constant power to these Yellow wires, the ECM doesn't have proper voltage, and the voltage that allows the Fuel Pump Relay to close never gets to the Fuel Pump Relay. You have a fault in that Yellow wire with the fusible link. It could be a bad fusible link, or a break in the wire.

What you need to do is attach a jumper wire directly from the Battery Post at the Starter Relay to either Yellow wire at the EEC relay. Try it with a long jumper first, and then turn on the ignition. The fuel pump should prime. If it does, try and find where the Yellow wire from the EEC relay to the fusible link fails, and repair it.

Take care,
-Chris