HI. I have a mid '80's ford dump truck with a 3208 in it. My issue is that if it sits for a week or longer it basically seems to lose it's prime (fuel). It will start right up and idle for about a minute or so. Then it starts to miss and flutter until it eventually dies. If I pump the hand pump before I start it then it starts and mostly runs fine. My question is, is there a check valve or something that is supposed to keep the fuel from bleeding back to the tanks? Thanks in advance for any and all advice.