Lack of pressure sustainment in gas tank

Car engine failed. The fuel pump was replaced. Car initially started but the pressure in the gas tank dropped and car stopped. It can be restarted but won’t continue to run.

Could you explain: “the pressure in the gas tank dropped” Who (mechanic, dealer, neighbor?) decided the pump needed to be replaced? Was the “new” pump new or remanufacture?

re-manufactured pump from Advanced Auto, second one. There is no build up of pressure in the gas tank to feed gas line. Hooked up shop vac. & blew air into gas tank and engine will run but dies if air stops.

If I am understanding you correctly, it sounds like your car (which at this time is a mystery car (Make model & year please) you may have a problem with the vent system.  Have you been in the habit of topping off the tank when you fill up?

The fuel pump doesn’t pressurize the gas tank, just the gas into the fuel line. Your still having a problem with the fuel pump. Did you check to see if the fuel pump is getting power? There is a relay and fuses that also need to be looked at, as well as condition of the contacts at any of the wire harness connections.

  1. What year/how many miles Focus?
  2. Has the fuel filter ever been replaced?
  3. How was it determined that the pressure was insufficient?
  4. What codes did the OBDII system produce in conjunction with the problem?
  5. Just prior to the problem, did the car ever hesitate/run rough? Under what conditions (in particular, what throttle openings, fuel tank levels, and nose up/down attitude)?

I think that the vent problem sounds about right.

I don’t think so. A vent problem would be resolved just by taking the gas cap off. The OP is forcing air into the tank to force gas into the engine. It sounds like the fuel pump or regulator isn’t working.

Did you install the pump yuorself?
Have you confirned voltage to the pump?
Have you checked the output line of the pump for pressure at the pump?
Did you change the fuel filter?