Probably. Although, I think the canister on these trucks is supposed to be hooked up to a bowl vent, not a vacuum port as it previously was.you must have a pressure issue , is the charcoal canister full of gas?
F150s have been made for so long with such sweeping changes along the way it is sort of difficult to figure this stuff out. Additionally, 85 was a split year. Halfway through they went to EFI so that further complicates stuff.
40s are not this confusing and the Toyota FSMs are soooo much better than Ford's.