By James Goss      Update… It has been about three months since I wrote the above article on fuel tank pressure and I now have the outcome of that project. The check valve has been installed on several engines with the same results in each case, improvement in the overall operation.  A more reliable idle and better acceleration is common. With the reasonable price and quick installation time, about one minute, why not use one. If a cowling surrounds your engine, you will need to insert a plastic tee on the tank side of the valve and then plug its take-off line. This line will be used when filling the fuel tank. You will unplug this line so air can escape the tank as fuel goes in. Also when you kill your engine removing the plug can exhaust the pressure in the tank.  Good luck!