bucket (loft, lift, arial) trucks

second-gen_monkey

i hope this in the right place...

a have a question refering to a 92 Ford f800 based 42' (i beleive) bucket truck with a cummins 175b motor (if i'm wrong i'll fix it tomorrow but i beleive thats it). the truck idles around 500 rpm but should be at 750. if i engage the pto it jumps to correct idle for the pto but once it's off a couple seconds later its back to 500. i was told there is a selenoid behind the fuel pump that may be sticking. i see one there but it seems to function right, however there is an adjustable nut on the bottom where the armature connects to what appears to be a fuel flow valve, which way should i adjust it? i don't want to accidentally cut fuel and burn my pump, it's apparently a good pump from what i've heard and i don't want to drop 2 to 3000 plus the time it takes to R&R it because i did something stupid.
the manual primer also appears to be a little leaky, there's a film of fuel and when i replaced the water seperator/ fuel filter it didnt prime well, i think i heard air and we started it with ether and it started just fine and hasnt hard started again. would this cause air to be pulled into the system during operation? could this be my true problem?