Question about 1987 Pontiac Fiero

2 Answers

I'm having trouble starting my '87 Fiero. Everytime I leave it sit for more then an hour or so, It takes about 20 seconds of cranking to start. Once started it runs perfect. Basically I'm losing fuel pressure when it sits. Is there an accumulator that holds the pressure or a check valve somewhere that prevents the backflow of fule? Not sure if one of these pieces exist on this car? Would it be the fuel pump, even though the car runs perfect once started? Thanks

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  • shaneb700 Jun 22, 2009

    If it was timing or engine sensors wouldn't I have issues with the car running as well? It runs perfect, lots of power, no hesitation, etc. It's only on start up, when it sits for more then an hour. If I shut it off at the grocery store and come back out 20 min. later, it fires right up. I haven't done any work to the car as it's new to me. I'm thinking fuel pressure is getting slowly lost when it sits and I have to crank the car over until it builds back up. What would be the cause of fuel pressure loss?

  • shaneb700 Jun 22, 2009

    I'm looking for more help as to what would cause fuel pressure loss, when my car sits for more then an hour.

  • shaneb700 Jun 22, 2009

    it's the 2.5l 4cyl motor. does the fuel pressure regulator keep the pressure in the line while the car is off?

  • shaneb700 Jun 22, 2009

    You've been super helpful. So, if I had an obstruction in the fuel line, wouldn't the car always have trouble starting and also running? Remember it only has to crank over when it has been sitting for more then an hour and then always runs perfect. Does it sound like a fuel pressure regulator to you or something else? Also you mention the fuel relay switch, but that's electrical, which wouldn't have anything to do with the car losing pressure when it's shut down right?

  • shaneb700 Jun 22, 2009

    Man, you're awesome. I'm feeling this solution. Just a couple more questions and I'll leave you alone. Where is the relief valve located, so I can replace that, and you mention the fuel metering gasket and the tube module assembly gasket, where the heck are those things? I'm going to replace all fuel line, all the way to the tank, replace the fuel pressure regulator and these other things you mention and I bet that will do the trick.



    Thanks

  • shaneb700 Jun 22, 2009

    This has been amazingly helpful. Thank you very much.

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  • Master
  • 6,784 Answers

HI. this sounds more like an obstruction in the fuel lines or a faulty fuel pressure regulator. i recommend doing a fuel pressure test. the pressure should be at least 9-13 psi. If not, check for crimped lines or disconnected electrical connectors. this readings are for the 2.5L Engine.

You would check the pressure, by connecting the pressure gauge on the
filter inlet pipe on the fuel rail assembly when dealing with the 2.8L Engine.You would need to remove the fuel pressure regulator of course and bleed the system as well. the reading should be 40.5-47 psi (280-325 kPa). be sure to turn the ignition key in th on position and, let the pump run for 2 seconds. If pressure is low or zero, check for a restriction or blocked fuel line. Also check the pressure regulator and the pump relay as well.

If you could let me know which engine you are runinng, this will help. is it a 4 or 6 cylinder?

Which liter?

Thanks,

Posted on Jun 22, 2009

  • 4 more comments 
  • Michael Masters
    Michael Masters Jun 22, 2009

    Yes, there is a diaphragm that ,ay ruptured in your case that is part of the regulator. your Model is equipped with a Model 700 throttle body. here is a little description of what it consist of so that you can understand it a bit better.

    The Throttle Body Injection system used by the 4-cylinder Fiero uses
    an electric fuel pump. The throttle body is placed on the intake
    manifold where the carburetor is normally mounted. The TBI unit is
    computer controlled and supplies the correct amount of fuel during all
    engine operating conditions.

    The unit is made primarily of aluminum and consist of two major casting assemblies, a throttle body and fuel metering assembly.

    With
    the TBI system, air is drawn into a single bore. The fuel is then
    injected into the air stream under pressure. The unit contains a
    pressure regulator Idle Air Control (IAC) valve, and an electrically
    operated solenoid that activates the fuel injector. Also attached to
    the TBI is a Throttle Position Sensor (TPS), a fuel inlet and a fuel
    return fitting.






  • Michael Masters
    Michael Masters Jun 22, 2009

    If the pressure test are low, i would replace the fuel pressure regulator.

  • Michael Masters
    Michael Masters Jun 22, 2009

    This is true. i really don't sense any volume or, pressure issue here. the case is escaping pressure and, this could only be caused buy a faulty relief valve or a damaged pressure regulator. the fuel metering cover gasket could be leaking a well. I would also replace the tube module assembly gasket.

  • Michael Masters
    Michael Masters Jun 22, 2009

    If the lines are not leaking and, the pump is not obstructed, this will lead me to believe that the issue resides within the throttle body and, the main suspect is the fuel pressure regulator.(ruptured diaphragm)

  • Michael Masters
    Michael Masters Jun 22, 2009

    Ok, the fuel metering assembly is just the top assembly that is attached to the throttle body. there's a gasket that is in between the throttle body and metering assembly. I just confirmed that the relief valve is not an issue with this engine. the 2.8L has the relief valve. you have the 2.5L so, this is not an issue. don't worry about that on your engine. Next, the Tube module assembly gasket is located just in front of the throttle body assembly under the pressure regulator. In fact, its just below the Idle air control valve. I will place a link below that will direct you to a exploded diagram of your throttle body build. i recommend replacing one more additional gasket and, that would be the flange gasket.

    Remember. the fuel metering assembly and the actual throttle body are two separated Assembly's that are joined and, there is a gasket that is called the fuel metering gasket that is between the throttle body and metering Assembly. it will be on the diagram below.

    CLICK HERE FOR EXPLODED DIAGRAM


  • Michael Masters
    Michael Masters Jun 22, 2009

    Doing the line replacement all the way to the tank, is a very smart move:)

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  • Master
  • 355 Answers

It could be a lot of things. one of the engine sesnors could be bad giving the computer a bad input and then it will not allow it to run. You could have an issue with low fuel pressure or bad gas. if you did some engine work to this the timing could be way out of wack. these are just a few of the possabilities let me know what lead up to this so maybe I can help you out further.
good luck :)

Posted on Jun 22, 2009

  • Rohit  Asthana
    Rohit Asthana Jun 22, 2009

    you can find now manual in fixya too

    http://www.fixya.com/cars/p695391-pontia...


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