When u put small amount of petrol it doesn't come up on the meter. I had 30km left. I put $5 petrol and meter didn't change but should end up with about 55-60km in the tank but stayed at 30km range.
The fuel gauge in the dash is not very accurate. If it was working before I suspect your fuel sending unit is faulty. Most Fords are located in the fuel tank as part of the fuel pump assembly. They wear out over time.