Was driving in my 98 blazer 4x4 when I heard a loud thump I was looking around and seen that the gas tank is now in the shape of a n I pulled the gas cap and had trouble from all the vacuum behind it please help with what could of caused it I do know I have a check engine like on for a code p0452 other than that I have no idea what would cause that

 

That is wild. I never heard of that, Im guessing it has to be an issue with evap. The truck is not getting rid of the excess vapors in the tank. When the vapors condense, it would cause negative pressure. Thus imploding the tank. you mention a p0452 pressure switch error. Maybe the switch is faulty or the wiring to the switch?

 

The evap system is connected to engine vacuum where a purge valve near the intake manifold opens to allow engine vacuum to start lowering the pressure in the system. At the other end, the evap solenoid opens, and that allows fresh air into the system, which then passes through the charcoal canister And helps to sweep the stored gasoline fumes back up into the intake manifold to be burned by the engine. There’s some testing functions, for instance the purge valve will open and the evap valve will be closed and the pressure sensor in the tank is expecting the pressure to drop And then hold for a specified period of time. That system can fail in a few different ways. It can leak, there can be blockages or there can be valves that do not operate correctly. In your case, the purge valve was opening just fine and the error code is because the system went into a state where it did not expect a strong vacuum to hold Because the vent valve should’ve been opened. All of the line should’ve been clear and the charcoal canister not obstructed, but what most likely happened in your case is that either the vent valve did not open or there’s an obstruction in the charcoal canister or one or more lines which allowed the engine to pull and hold a strong enough vacuum until the tank started to implode. Normally, when there is a code involving a sensor, I will caution that the sensor can always be faulty and the reading not legitimate, but your sensor works perfect because it reported a low voltage when there should not have been one meaning there was excessive inappropriate vacuum, which is evident by the tank condition. Extreme temperature changes in the tank can be a contributing factor because pressure changes with temperature in a fixed volume. You’ll need to replace a failed evap valve or, clear lines or the charcoal canister.


George