How does a wastegate work?

[kidcharger]

The 1995 6.5td is complex.After replacing the IP,the turbo,injector,the truck still smoke black & no power.Nice idle but lots of smoke in acceleration & no power.28hg vacuum pump,15hg at wastegate actuator.
MY question:where the wastegate rod should be at idle?If I hold it to the firewall I notice less smoke.if I hold it to the front engine,lots of smoke.the actuator pull the rod to the front of engine but does not push back to the firewall,is it normal?I do not know how to check the boost.Should the actuator have a spring loaded to close the wastegate?:confused:

[DmaxMaverick]

Your wastegate (OEM 1995) is not spring loaded. Vacuum holds it closed, until the PCM reduces WG solenoid modulation, reducing the tension against the WG, allowing exhaust gas pressure to bypass. If you have good vacuum at the actuator (15" Hg), you should not be able to move it easily by hand, and you should be able to develop boost (decreasing smoke). If you have good vacuum at the actuator, and are not developing boost, either the actuator is bad, or your turbo is bad. You should not be able to easily move the WG linkage with 15" vacuum at the actuator, so if it's loose, it's bad.

[kidcharger]

Thank you all for info.After all the checking procedure,wastegate,solenoid,vacuum,intake,fuel,I suspected the PCM did not communicate with dash.only code 12.So I tried to unplug some engine solenoid,EGR,Wastegate, so the PCM could communicate & put a DTC code.When I unplugged the MAP sensor The engine light went ON & truck did not smoke anymore.I went for a road test & perfect.NO more black smoke,good power.I Replaced the MAP sensor & truck works well.