I recently bought an 88 f350 460efi, it has a propane conversion installed already(impco model e), but it does not seem to be working, i disconnected the fuel line going to the conversion and propane is being supplied to it, I also opened the bigger compartment which i think is the mixer/carburater, everything seems to be in working order inside, there dosent seem to be anything electronic about this, besides 2 little valves which i assume are the vaccums, the one going into the mixer seems to work because it clicks when i connect it to a power source, the one which appears to be an outlet for fumes or something dosent seem to make any noise when i do the same, could this be my problem.... there is a switch on the dash also which says "gasoline/alt fuel" which appears to me that all it does is turn off the fuel pump. anyone know anything about this, I couldnt find a manual or installation guide on this product online. thanks..

ps. when i turn my propane tank off and disconnect the line it seems that propane constantly flows, how long would it take to bleed a 3/8" 12 foot line... dosent seem to me like it should take long....