I Need Help.

[Cbook]

I have a 1997 Toyota Surf with 135,000 Km. It has a petrol engine with 4 cyl 2690cc. About one month ago,one of our staff mistakenly put some diesel in the tank. He realised his mistake before driving, dropped the tank, cleaned and replaced with clean fuel. Since that time, we have had a problem with fuel backing up through the vent line into the emissions canister mounted on the sidewall of the engine compartment and leaking out the canister drain line. This can happen at any time, including when the engine is cold but if the vehicle sits in the hot sun and pressure in the tank builds up. The only solution we have found to the problem is to leave the fuel cap loose. The problem persists even if the tank if half empty.

Does anyone have an idea what our problem may be?

Thank you