Were is the solenoid switch on e-150 ford van v-8 1999..?

The solenoid switch on a 1999 Ford E-150 van with a V8 engine isn't a single, easily identifiable switch like you might find on older vehicles. Instead, the function is integrated into the Powertrain Control Module (PCM). There's no separate solenoid switch to locate.

The PCM controls the starter solenoid electronically. If you're having starting problems, the issue likely lies within the PCM, the starter motor itself, the wiring between them, the ignition switch, or the neutral safety switch (which prevents starting unless the transmission is in Park or Neutral). You'll need to diagnose the problem using a multimeter or a professional diagnostic scanner.