My bone stock 1977 Corvette (350 ci with automatic transmission) with about 90K original miles on it passed the tailpipe emissions test part of the California smog test, but failed the "evaporative emissions" part of the test.

From what I understand, to do the evaporative emissions test, they pressurize the fuel system (by taking off the gas cap and attaching their device to the fuel fill pipe?) and check for a leak down of pressure. If there is a loss of pressure, then there must be gasoline vapor escaping into the atmosphere.

So my question is, what is the likely place for this leak and how can I fix it?

 

Charcoal canister and its valve and then all associated hoses.

 

Since you pressurize the fuel system, you need to inspect ALL hoses, clamps, and tubing of any sort.
(Related to the fuel system , that is.)

 

Thanks for the replies. The Corvette has been up on jackstands for the last two months waiting for me to crawl under and check the hoses etc. I also have what I believe is a universal joint going out (whump whump whump...) so I will be checking that as well while it is up in the air. I replaced the Y-tailpipe back from the converter about a year ago, I wish I had known about the evap leak while the old Y-tailpipe was out because things are really tight up there...
In closing, I appreciate all the help and encouragement. I am not a flake, I will post back what I find and how I fix it, I am just slow and other "fires" seem to keep popping up requiring my immediate attention.

 

The noise you describe sounds more like it might be a rear wheel bearing. U joints tend to squeal as they go bad due to lack of lubrication.

 

73shark: Thanks. I will report back when I check it. Is there any check for wheel bearings I can do with the rig on the jack stands?

 

You can try rotating each rear wheel by hand to see if you can feel any chunking that might be indicative of a bad bearing. You can also try grabbing the wheel at the top and bottom and shaking to see if there's any excess play in it.

 

Check drive shaft "U" joints and the axel shafts' "U" joints.

And something many people ignore,.......

Check the center mount for the differential.
Them suckers will drive ya nuts tryin' to find the clunk.
It's been mistaken for loose exhaust, bad "U" joints, and bad wheel bearings.