I have been reading and testing to verify extreme pressure in my gas tank. After driving car I can hear the tank groaning, opening the cap relieves the pressure. So I performed some of the tests recommend here - removed the pressure/vent valve located near gas tank, once removed a small amount of air blew out - so the tube itself is clear and holding the couple of pounds of pressure as it should. The valve itself seemed in working order (applied pressure and vacuum), cleaned and replaced.

When I test the lines at the charcoal canister, the vent and vacuum lines are fine, when I apply compressed air to the tank line (with gas cap off), I get blow back, the compressed air will not pass through.

First, should I be able to blow air through the "tank" tube at the canister?
Second, any thoughts on where the clog could be located?

As always, thanks for your attention and advice.

 

Yes, but a limited volume. There is a restriction in the sending unit at the tank.

Most likely the restriction in the sending unit is clogged. There is also a roll-over device that sometimes gets jammed. Basically it is a ball that blocks off the CCP vent in the tank to prevent fuel from pouring out if the car goes belly up.

If you can get even a small amount of air through the vent line back to the tank, spray some solvent into the line and blow it through. With some luck you will be able to clean the clog out and not have to drop the tank.

RBob.