I have a 1988 Ford F-250 with a 5.0 302. I was driving home and my rpms dropped to zero while on the gas and it was like I turned the key off and it died. I just got the truck. Could it be the pcm? Pickup coil? I really need some help.

 

does any power come on when key is turned on? If not might check fusible links at solenoid. I had that happen once on my 86.

 

have you checked battery voltage ?
if it's below 12.5 volts or so, try jump starting it with another vehicle and then check alternator output.

 

Blown fusible link is very possible, but I would also check fuses.

 

The title of your thread says "not cranking or starting" but your post says nothing about either, just that it died while running. Given that it died it would stand to reason that it wouldn't start either, and could be anything (although the tach dropping to zero indicates that it's affecting the ignition).

But "won't crank" generally means that it doesn't turn over when you engage the starter. That would tend to mean the starter isn't getting power which wouldn't cause it to die unless the entire truck completely lost electrical power.

So if you meant what you said in the title, then I'd look for a broken battery cable, a REALLY corroded connection or a completely dead battery.

FWIW, I had that happen on my '02 diesel. The alternator had died and eventually the batteries ran down to where the PCM wasn't happy and the engine died. When I tried to restart it obviously it wouldn't turn over (crank) with the batteries that dead.

 

Unless gassers are very different, the PCM has no control over the starting (cranking) circuit. So if it stalled, and it won't crank, and there's a single underlying cause of the two, then it would fall into one of three general possibilities:

* Main power / ground / fusible link issue (see above). This would affect both starting and running circuits. Lots of places to check there; the ignition switch can't be ruled out
* Extremely discharged battery and inop charging system (see end of post #5)
* Seized engine crankshaft - try to turn the engine by hand.