OK,Bought this from a buddy of mine.96 Jimmy,one owner before my buddy,have all service records,truck is in excellent condition,little over 100,000 miles.He bought a good running truck,with a fuel smell around it.Nothing on the ground,but you could smell it.Installed new tank,and pump.He buys all of his parts from NAPA and buys the good stuff so I assume the electrics are Echlin.Started acting up randomly after that.Installed new cap,rotor,plugs,fuel filter ect...Still randomly acted up.Told me it would get very rich.He did not feel like messing with it anymore,so I bought it.It ran great when I brought it home.Got it cheap,so I threw a couple parts at it,new ign module and coil,both Delphi.Also installed the upgrade fuel Standard Motor spider.The fuel spider made a huge difference in the way the truck ran and ideled.Ran great...for 2 days.Today it did what my buddy described to me.Got so rich it started missing badly,could barely keep it running.Got it home and fuel started running out of the canister vent valve and somewhere else near the transfer case.To me,it seemed like it was just dumping fuel to the motor.I know dropping the tank is a no brainer,but what could cause something this severe,but be totally random?I have worked on lots of vehicles,but have never seen anything like what I saw today...Also,no codes.Tank had pressure or vacuum when I released the cap.Not excessive,just told me it was not leaking.Please help.

 

I would look into the emissions/evaporative system from what you've stated.

 

Is fuel coming out of the valve something anyone else has experienced?I thought vapor was the only thing that was supposed to get to it.

 

Was it constantly topped off with fuel to the top of the filler neck? Is it possible the charcoal canister is full of fuel? I check the fuel return line and make sure it's ran correctly to the tank too