Gas tank problems

Kimsimms1234Kimsimms1234 Member Posts: 1
edited March 2019 in Pontiac
I have a 97 pontic grand am as long as i keep a full tank of gas car runs fine and gages are right but as soon as it drops to the line right below the full it act as if its running out of gas but it has gass and again gages are right and new full pump


  • imidazol97imidazol97 Member Posts: 26,743
    I have no way of checking to be sure the new fuel pump is delivering the right fuel pressure. A pressure slightly below required can give strange symptoms.

    Are there any check engine lights coming on and staying on steady, which is typical of an emissions system item needing checked and fixed?

    But assuming it's a working good fuel pump, I would suspect something was keeping the fuel from getting from the pump to the engine.

    That could be a problem with venting of the tank. Has the gas cap been replaced with a different cap that doesn't have the correct venting ability? My suggestion for ME would to leave the engine running when it acts like it's not getting enough gas and unscrew the gas cap, listening for an intake of air, which might mean the cap isn't venting as fuel is taken from the tank or the purge system is operating using vacuum to pull air through the carbon canister.

    You could have a clogged fuel filter. But it should give symptoms based more on time spent running in each use of the car. How many miles on car? Do you know if the fuel filter had even been replaced--usually they don't need to be unless low quality fuel has been used.

    2014 Malibu 2LT, 2015 Cruze 2LT,

  • Mr_ShiftrightMr_Shiftright Member Posts: 64,482
    In addition to the excellent suggestions above, I think I'd start right off by slapping a fuel pressure gauge on the fuel rail and seeing what's what.
  • imidazol97imidazol97 Member Posts: 26,743
    I wonder if the full tank connection is actually a false clue.

    I agree that it would be good if someone puts a fuel pressure tester on the engine and checks the pressure. Also when the engine is revved with the tester connected, the fuel pressure should rise while the vacuum drops as the throttle plate is opened. But as soon as the engine speed increases like it is testing in Park, that vacuum increases and the pressure drops back to normal.

    I suspect that engine has what the 3800 engines had and that's a pressure control valve on the gasoline line on the engine. It has a single vacuum line to it and it increases the fuel pressure for better performance when accelerating under load. Those have a setup that can leak extra gasoline past the restriction part when they age or go bad.

    Also your problem could be injectors or spark plugs and even wires.

    Does the orange check engine light come on or go on and off?

    What do you mean by "gauges are right"? Do they change their readings when vehicle is acting up?

    2014 Malibu 2LT, 2015 Cruze 2LT,

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