84 Full size - if 'resistance wire' is bad car dies when key is moved from start to run.

Howdie - I found this post from 10 years ago. I have this problem but think the post is a little bit inaccurate as the wire off the starter relay is the one that does not use the resistance wire.
If I put 12v into one of the little wires off the starter relay my car continues to run - this wire normally losses power then you come off the start position. Any BTDT?
Make sure you are getting voltage to the pump before you replace it. I have an 85 Grand Marquis (same basic car) and it sends the full 12 volts to the pump while the key is held over to start but feeds the pump through a resistance wire from the starter relay after you let go of the key and it returns to run. If the resistance wire breaks the engine will start but die immediately when you let go of the key. The resistance wire on my Merc. is yellow and had printing on it every few inches that says "resistance wire". I have heard of blue wires on fords. To find the wire just follow the positive battery cable to the starter relay and look for a very stiff wire about 1/8th of and inch in diameter connected to the relay.
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Ok, assuming that you mean that the car cranks, fires, and then dies as soon as the starter drops out ...
There will be a ballast resistor, usually a length of wire run along the bulkhead under the windscreen, probably with bullet connectors. This is where your problem lies - It's faulty.
The car is designed to run very lean, and as a result can be a b*gger to start. So Ford fit a lower voltage coil with a ballast resistor in series so that it runs correctly from the 12V battery.
However, there's no way it will start, so the ballast resistor is shorted out when cranking and giving the coil a higher voltage and stronger spark.
So the car cranks, fires, then dies because as soon as the (faulty) ballast resistor is put back in series with the coil, the spark dies.
I had exactly the same problem with an ancient Fiesta many years ago.
HTH.
Al.
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