My starter is activating but its not cranking.

The fuel relay will activate for 3-5 seconds every time you turn the key on. It should not keep the engine from cranking. I have seen problems with the ignition switch that will keep the truck from cranking. Make sure that the battery connections and clean and tight. Check to see if 12 volts are getting to the starter when you try to crank it. Hold the key in the start position and while holding it, strike the starter with a hammer. If it starts , replace the starter.

Wiring, schematic, electrical diagrams, fuse diag, error codes etc are basic contents of these online books they have here on this website www.reliable-store.com I have attached. Must check it out

What year ? For the 2004 model year, the Windstar was renamed the Ford Freestar. Anti-theft light lit on instrument cluster ? Battery good ! How about the battery cables ? Voltage drop test the starting system . Videos on you tube Starter Voltage Drop
Starter System The starting system cranks the engine at a speed fast enough to permit the engine to start.

• Heavy cables, connectors and switches are used because of the large current required by the starter motor (11002) while it cranks the engine.
• The amount of resistance in the starting circuit must be kept to a minimum to provide maximum current for starter motor operation.
• A discharged or damaged battery (10655), loose or corroded connections or partially broken cables will cause slower than normal cranking speeds and may prevent the starter motor from cranking the engine.

The starting system includes:

• the permanent magnet gear-reduction starter motor with a solenoid-actuated drive.
• the battery.
• a starter switch (part of the ignition switch (11572)).
• the transmission range (TR) sensor.
• The TR sensor in the starter control circuit prevents operation of the starter motor unless the selector lever is in NEUTRAL or PARK.
• Starter Relay-Interrupt The starter relay (14N089) interrupt-consists of:
  • pull-in coil and
  • contacts.
  When the ignition switch is in the START position:
  • Current passes through the starterrelay-interrupt from the engine compartment power distribution box to the starter solenoid (11390) .
  • Anti-theft controller module activates relay-interrupt.
  • Pull-in coil in the starter relay-interrupt is activated and pulls the contacts apart.
  The starter relay-interrupt is deactivated when the ignition switch is in the RUN or OFF position.
  

When you use the ignition key you activate both the starter and ignition circuits. When you jump the starter motor all you do is crank the engine - you have not energized the ignition so car will not start.

look under hood fuse box and replace tha starter relay if you have a relay that looks the same you can swap them and see if the relay is bad.

There is an ignition/starter switch on the left side of the steering column that activates the starter solenoid.

check starter check for low battrey volltage

The starter has always had a solenoid to conduct the correct current to crank. the click you hear from the solenoid activating to close the contact for the starter. However the contacts inside the solenoid are corroded due to arcing after several times of starting. When this happens, there is high resistance through these contacts hence low current to the starter not enough to crank. The solenoid needs to be replaced. If they don't sell a separate solenoid then you have to replace the integrated starter.

Battery or starter. Sometimes the battery will have enough power to activate fuel pump and dash lights but not enough to turn starter.

Fuse would be in the outside fuse box. Look for the one labeled starter. If you are not getting power to the starter, could be an ignition switch.