No doubt your mechanism needs rebuilding. I suggest you start by purchasing a copy of my Service Manual, actually, I am going to rename it "ECO Restoration Manual." The reason for this is that I took the old manual and rewrote it, first using language you can understand, and putting all sections in the order you would use to rebuild the mechanism. This manual also includes information if you are just repairing one item.
We also offer a service where you ship the mechanism to us and we completely rebuild the unit, and send it back looking brand new, calibrated to within one pound and it is guaranteed to work. I have personally restored over 500 of these meters, plus we have also have rebuilt over 550 of the mechanisms for customers.
We also offer parts used in the restoration. All this can be seen on this page of my website: http://petrolianacollectibles.com/eco%2090%20parts.htm
I am also the author of the Gas Pump Bible and the Air Meter Identifications books, they can be seen at: www.gaspumpbible.com