I have a 1987 F-150 with the 4.9L in-line 6. It idles rough and when i pulled off the vacuum canister it was FULL to the top with gas. Any ideas?

 

Is this truck fuel injected or with a carburetor ?

 

Fuel injected. I have replaced wires, rotor, cap and plugs.

 

Normally, only fuel vapors are supposed to get into the canister. There is only one way for liquid to get into there and it is from the vapor line that comes from the tank to the canister. If the fuel tank was getting consistently topped off to the limit it has to go someplace and the canister is the place. There was supposed to be a check valve to prevent liquid from going in there in the event of a rollover and it is possible that the valve couldn't do it's job. Have you been filling it to the very top frequently?

 

Its the canister that looks like a V8 juice can on the left side on top of the fender. I cant find anything online or in the book about it. Both of the lines to it go to a unit on the side of the intake manifold. This is also where the line for the brake booster vacuum goes. The vapor canister is in perfect working condition. I have only had the truck for a month and have never put more than $20 in either tank. This is not my image but you get the drift.

 

That beautiful juice can is a vacuum reservoir. If fuel is getting in there it probably is getting in there because of a leaking fuel pressure regulator. Remove the vacuum hose from the fuel pressure regulator. If it has fuel in it too, replace it.

 

I will check that out thank you. Would the A.I.R. pipe not being installed make a difference? Mine is not there.

 

Because there were a few pipes, where is the one you are concerned about?

 

All I have is the hose that connects to it nothing else is there.

 

From what I think I see in the pix,
That hose should come from the air pump and connect to that check valve just below it.
Air from the air pump goes to that check valve when the engine is cold and down to the exhaust manifold ports to complete the combustion process. Once the engine warms up, that air is diverted to the converter. Temp controlled vacuum valves control that.
Someone may have disconnected that hose for whatever reason. Those check valves had a habit of burning out or rusting and had to be checked regularly. The check valve was to protect the hoses and air pump in the event of a backfire. There is quite a process as to how the air was controlled but when working as designed, it did the job.