William H

Recently had the fuel icon start flashing whilst towing a van, had about 1/4 tank of fuel still. Added more fuel and light went out, only to come on again some hours later. Flashing again. Just for clarity, this is not the fuel light on rhs of speedo with water indication. Its on the left side. Have changed transfer tank filter thinking this might be the problem, no good. Does any one have any bright ideas. Maybe fuel pump in tank? Vehicle has done 167k fuel pump not replaced.