my 1977 300d will not start. the 300d runs perfect when started -if i can get it running. the fuel keeps getting air int the lines. so, i changed the lines and put new crush washers. the line that runs from the secondary filter to the injection box has a hissing noise when bleeding the air from the lines. then a few minutes later, i can see air in the lines. the problem started a few months ago,. i had to use s starter fluid to get the car to fire. the problem just kept getting worse. i'm just looking for the best place to start with-out wasting a lot of money.

andy