My inline 300 six runs great at 75°+ outdoor temperature, but when temperature drops or humidity goes up it runs like crap. I replaced spark plugs, wires, cap and rotor no change.
At 75°+ outdoors temperature my truck runs great,
but when humidity goes up or temperature goes
down the truck idles fine but has no power. When it
sets for 2 or more days the gas drains back in to
the tank. So I have to turn the ignition on several
times until I hear the fuel pump change pitch then
it'll start.