I had my 300zx in storage over winter. Now that I've gotten her out, she isn't registering any boost whatsoever. I can hear a small boost leak at idle, haven't had a chance to hook up a compressor to find it exactly, but I didn't think that would cause me to get zero boost. I can hear a grinding noise and a slow spin coming from the driver side turbo revving it at about 3.8 rpm. She doesn't smoke at all and the turbos only have approx 6k miles on them and never really driven hard. Does that indicate that the turbo is totally shot? And if it is, would the other turbo be unable to produce boost until the other is replaced?

 

If even one turbo is bad, you won't get any boost at all. Grinding noise does suggest a bad turbo. The only vacuum leak that'd kill a boost reading is the one going to the boost gauge - if that one is in tact (it goes across the firewall and connects by the driver's side fender), you have at least one bad turbo.

 

The gauge functions properly. It reaches zero and stops. It's not producing any boost at all.

 

Hate to be the bearer of bad news, but you have a blown turbo.

You say they have 6k miles on them... new, rebuilt, what?

There is one *tiny* chance that it's not a blown turbo... check the intake pipes (specifically, the hard pipes that go from the turbos to the intercoolers... just wiggle them). If one of them is loose, it could leak enough air to cause that problem while still run ok.