I got a 79 pickup with a 400 engine. I noticed that the clear fuel filter fills with gas, then goes nearly dry and fills again (while engine is running). Is this normal? Shouldn't the filter be constantly filled? I also have a problem where the truck acts like it's going to die from a lack of gas, particularly under load and on hills. I am wondering if the fuel pump may be weak..... ???? The carb was rebuilt about a year ago, and is tight to the block with no vacuum leaks, since I just replaced all the vacuum hoses.
Whether I rev the engine, or it's at idle, that filter tends to fill and empty regularly.