Caution! This photo may be disturbing! I pulled my fuel tank and found where the upper unit of the fuel tank body was full of perforations. Rotted. And this photo is just the first crud that came out when I tapped the fill line onto a metal pan. I can't save the fuel tank; I didn't know how bad it was rotted until I pulled it. Looks like I will have to order a plastic replacement.
My guess is that is your main problem the next is how far down the pipe did the rest of the crud go? It may well be near the fuel pump so I would put lots of air pressure down the pipe making sure the ends arent connected to anywhere you dont want the crud. Tony
Thanks Rusty Heaps and Modiol and everyone! My Tanks inc tank just came in this weekend. Decided to get steel not poly. Still waiting on new sending unit. May be able to install this Thanksgiving weekend.
Thanks for the update. Make sure you check the sending unit before you install it. Connect the sending unit wire to it and ground it to the chassis. Move the float arm through the full range and watch the gauge.
And make sure the unit is grounded when it is in the installed tank. Chevy always depended upon sending unit grounding to the tank and the tank grounding to the body or frame to complete the circuit. These steps will reduce the frustration factor! Don't ask how I know!
Also, I will be interested in your assessment of how well the replacement tank matches the old tank and fits into the car. I have had mixed experiences.