Have you checked the Cam Position Sensor (CPS)
This applies to all PowerStroke motors from late 1994 to 2002.
Diagnosis: A bad cam position sensor is usually signified by the PowerStroke motor abruptly and unexpectedly quitting. The motor may also be suffering from slight power loss and slight increase in fuel usage which is usually not noticeable until it is seen as an improvement when the sensor is replaced. When the CPS causes the motor to shut down, the tachometer will not register. If the motor fails to restart, the tachometer will not register when the starter is turning the motor over. This may or may not cause the check engine light to come on.
Part Numbers: The International parts are usually half the price of Ford's, and I wouldn't buy one from Ford unless you absolutely had to.
International part numbers:
A change occurred mid way through 1997, so if you have a 97 it is best to look at the engine serial number. For serial number before serial number 375549 use PN# 1821720C98. For serial number 375549 (including this number) and after use PN# 1825899C93.
Ford Part Numbers:
For 1996 and older use PN# F6T012K073A For 1997 and newer use PN# F7T012K073A
Remove/Replace: CPS replacement is a very simple process. It is located at the 10 o'clock position of the crankshaft pulley and secured with one 10 mm bolt. Removing the serpentine belt will facilitate the removal. Step 1) Make sure key is off and disconnect battery or pull #9 fuse. This is always a good idea when working on engine electronics.
Step 2) Remove engine belt
Step 3) Unplug wiring plug from sensor by prying out on the little plastic tab and pushing it out of it's socket
Step 4) Use 10 mm socket with small extension to remove 10 mm bolt
Step 5) Clean any dirt or grease off of sensor and surrounding area to prevent contamination of crankcase oil and seal of new sensor
Step 6) Use pliers, pry bar, or whatever else to gently remove sensor by pulling it straight out. It may be slightly stuck and slight force may be needed to loosen it. It is ok to twist it in its socket to loosen it if necessary.
Step 7) Coat new sensor o-ring with clean engine oil and press sensor into hole.
Step 8) Replace 10 mm bolt, torque to 10 ft-lbs, or just make sure it is snug.
Step 9) Replace wiring plug by simply pressing it into position until you hear the holding tab click into place.
Step 10) Replace belt.
Step 11) Ensure battery has been disconnected or #9 fuse has been out for at least 30 minutes. After this amount of time, they can be replaced.
Step 12) Start engine and inspect for leaks or other problems. Make sure belt has been properly aligned on each of the pulleys.