HELP - gas isn't getting to the fuel pump

[tricia]

I recently purchased a 1986 Chevy Scottsdale 4 wheel drive truck. Pump the gas twice and it would start right up and start immediately for the rest of the day. The only problem was the gas tank leaked so I took it in to get the tank replaced with a used tank. Unfortunately they sent the wrong tank and my mechanic couldn't find another anywhere (my truck has a 16 gallon tank). The original tank was already off so we decided to try patching it, which worked - it no longer leaks. He also coated the tank with some sort of underbody stuff.

It didn't want to start, however, after the repairs. Finally, they got it running and I took it home - set out to get hay and it kept killing. With the help of a neighbor I got it back home and borrowed the neighbor's truck to get my hay. My mechanic came out and found a kink in the fuel line which he fixed. I made one run for a roll of hay and then it sat for a week until I needed another roll of hay - once again I couldn't keep it running and then it wouldn't start at all.

My neighbor changed the fuel filter for me and he checked the fuel pump, which is new, and it is building pressure properly but only air is coming through, no gas. he blew into the gas line and the bubbly gurgle that should have been there was very very faint - not right at all.

Everybody is stumped as to what the problem is - the mechanic said that the lines that had to be reconnected are different sizes so there was no chance of crossing them - which was one of the things my neighbor thought might be the culprit. The mechanic thought there might be some debris lodged in the carbeurator but since no gas is getting that far I doubt that could be it. He also said something about it possibly being a vacuum line. I'm wondering if when they removed the tank the first time, expecting it to be trashed, they might have just dropped it or thrown it and damaged something - would that be enough to damage the float in the tank? It would seem to me that if air is getting through to the fuel pump, then some gas should be able to get through as well. Could something be causing a vacuum after the truck is run causing the line to kink again?

If anybody out there has any ideas on this I would really appreciate hearing them asap. The truck is being towed back to the shop, probably today and I am desperate.

I really will appreciate any suggestions!