Need evap help

Ok so about a month ago I purchased this 2005 dodge ram 1500 5.7L v8 hemi. I've been through hell and back trying to fix this problem and idk what to do. So there was no check engine light on when we bought it. We drove it 3 hours home and it ran great but after a day if driving the check engine light came on. We ran the code and it was P0457. Which is an evap leak checked the gas cap and it was brand new checked the lines under the truck and didnt see any holes or cracks. We took it to preferred mechanic (has horrible operation ours). And he said that the gas tank had a hole in the top. Sure enough we took it home took the bed off and there was a hole in the top towereds the rear and there was caulking all over the fuel lines attaching it the the pieces on top of the tank (not the fuel pump). And so we ordered a new one from the dealership and put it on and also replaced the purge valve (and cleared the code). We drove on a little road trip about 500 miles and when I got there the gas tank had collapsed in on itself and looked like an empty juice box. When I opened the gas cap I could hear it sucking in greatly from the vacuum that had been created at this point we replaced the sensor thingy that goes into the evap(charcoal) canister and cleared the code again. After that failed to fix it we gave up and took it to a shop. They said that the tank collapsing in broke the fuel pump so we replaced that and that the purge valve had failed so we replaced that they replaced a fuel line and said that should fix the problem. After a day the light came back on after that we took it back and they said to replace the charcoal canister which I did and then I replaced the evap leak sensor filter (that might not be what it's called). And I've driven it around a bit but the light hasn't came back on but the tank is still creating a very strong vacuum. Idk what to do I'm only 16 amd only knew so much

Do you have the correct gas cap?
That fuel pump is sucking fuel and pressurizeing it to the fuel rails, there should be a return line to the pump also.
Something is not hooked up right if the fuel tank is collapsed in on itself.

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Yes

Yes The gas cap was purchased from the dealership. So what do I check?

Kaleb hayhurst said:

Yes The gas cap was purchased from the dealership. So what do I check?

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Find the return line going to the gas tank and trace it back to the engine, look for a clamp that is squeezing the hose closed or a kink in the hose. If nothing like that, disconnect return line at gas tank, start the engine and see if fuel is running in to a bucket.

Just trying to think of the basics that would cause a fuel tank to cavitate.

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Copy and paste your original post over at www.batauto.com. they are master mechanics on that forum and they may have a better idea of what the cause is!

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