1984 Mercedes Benz 190e Won't get gas

Ran gas tank to low. After refilling gas tank won't start don't pick up gas even when priming it. Checked fuel pump and it is good so replaced fuel filter and it ran fine in tell I turn it off next morning has half a tank of gas but back to no start won't pick up gas to carb fails to start. Ran hot wire plus side of battery to pump car starts and runs fine turn it off and 4hr or so and back to no gas to carb again not sure if it could be the actuated can find a fuel relay in fuse box or other relays that are in front or behind fuse box where hayns or Chilton repair book shows it to be. No signs there ever was one there no disconnected wires in wiring harness or area. Can you give me a idea what to check or might be my problem.I'm a retired mechanic but don't know Mercedes and it was back in early 80.S when I was a mechanic and only acouple of years smog and brake lisened then. Cancer and age making me forgetful possible can you help me.I hope what am I missing to check