Vacuum pump

[scottfab]

That cycle time is way too short. The leak is too fast.

Here is some background on the secondary system on LT5s where the system is still in tack.
http://www.zr1netregistry.com/Inform...Diagnosis.aspx

First try checking that the pump itself is not the problem.
Do that by disconnecting the hose (be carful) and using your thumb plug
the side that runs to the pump. You can find a fitting on the
hose to do this where it goes over the two oil lines that
run to the radiator stack. The pump should run for a short time then
stop for as long as you plug the line.

If the pump runs again even with the line plugged then the diaphram on the pump has a hole in it.
Here is a pic of mine after I fixed it and fasioned a bracket to fit around it instead of glueing it back together.