why would i have to pump my gas to get my car to start?

Posted by 97-gst, Jun 29, 2010
Newbie Forum - Beginner/newbie/general DSM modification questions. First mods, how to run 10's when you haven't run 12's yet, any tech question that doesn't fit in another tech forum.

  1. 97-gst

    97-gst Proven Member

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    Radford, Virginia
    does anyone know why i have to pump my gas while starting my car?
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  2. housegsx

    housegsx Moderator

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    Because your carb is gunked up...

    Nah, maybe a bad isc motor or something. Do you need to do that all the time? Just when the engine is hot/cold?
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  3. DSMopar

    DSMopar Proven Member

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    Exactly what I was going to say :D
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  4. 97-gst

    97-gst Proven Member

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    Radford, Virginia
    Its got a new 1000 dominator carb on there, it cant be that.

    But really, i have to pump the gas everytime, no matter if its hot or cold, It doesnt matter to me it starts good once i pump the gas. Is this bad on anything?
    #4
  5. crash89

    crash89 Supporting Member

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    It could be possible that your stock FPR is going bad which is causing your fuel system to no hold sufficient pressure in the fuel rail.
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  6. beating4g63s

    beating4g63s Proven Member

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    beat me to it.
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  7. EclipticalGS

    EclipticalGS Proven Member

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    walker, Michigan
    The auto starter fluid canister has to be filled, its underneath the rear seat.


    Isc, fpr, fuel filter, boost leak, o2 sensor dumping gas.
    #7
  8. tsi1991awd

    tsi1991awd Proven Member

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    Puyallup, Washington
    Wowwww....I am shocked at the answers everyone is giving.

    You pumping the pedal is an illusion...it is the excessive cranking that you are doing that is allowing the car to start.

    Pumping the pedal will do nothing on an EFI motor. Pumping the pedal on a carbuerted vehicle works because it will allow gas to be injected directly into the carburetor where the magic happens.

    All you are doing is opening and closing the butterfly on the throttle body allowing more/less air to enter the engine while cranking.

    Your problem may lie in the fuel system...check the check valve by the fuel pump cover. Check the O-ring on the fuel pump output shaft inside the tank.

    Can't believe anyone hasnt said this....CHECK YOUR CTS. That may be the only cause. Bad CTS's are notorious on DSMs and they make your car very very hard to start.
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  9. SlushBoXRacer

    SlushBoXRacer Proven Member

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    i would say it could be a fuel issue FPR or pump. . but pumping the gas on a fuel injected engine? fail.
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  10. housegsx

    housegsx Moderator

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    Greensburg, Pennsylvania
    If it is the ISC then pumping the pedal would do something. If it is not opening at all, cracking the throttle plate will allow air in.

    OP, does it eventually start if you just crank it long enough without pressing the pedal? I don't know about the FPR leak being an issue either, as mine doesn't hold pressure long, but always starts right up.
    #10
  11. 9!'clipseDOHC

    9!'clipseDOHC Moderator

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    El Paso, Texas
    What is a CTS? I'm having a similar problem. I have a rewired Walbro 255 and a Bushur/SX AFPR, the rest of the fuel system is stock. I have had both for the last 5 years with ZERO problems. I changed the turbo 2 weeks ago and arced the alternator, ever since then its been hard to start. I instantly have ZERO fuel pressure after shutdown. I started a thread about it but no love.
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  12. tsi1991awd

    tsi1991awd Proven Member

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    Puyallup, Washington
    The CTS is the Coolant Temp Sensor. It sends the temp of the motor to the ECU so that the ECU knows how much gas to pass through the injectors to start the motor for the given temperature.

    When these fail (which happened on my other DSM), they will read open continuity and will be hard to start. These have a certain resistance, something like 2000ohms at 70* or something like that. If the resistance isn't right, the ECU will allow for less than sufficient fuel injection at startup.

    I would check the resistance between the two prongs on the CTS (located on the thermostat housing) to see what it reads. Keep checking it as it warms up....as it warms up, the reading should get lower. If nothing changes then it's shot.
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  13. ChillinGST

    ChillinGST Proven Member

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    Clearwater, Florida
    Throttle Position Sensor was first thing that came to mind. I'd check it out with a multi-meter.
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  14. 9!'clipseDOHC

    9!'clipseDOHC Moderator

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    Oh ok. I've been thinking that its electrical since it first started after I arced the alternator. Is there a relay or fuse for the CTS that might have blown?
    #14
  15. tsi1991awd

    tsi1991awd Proven Member

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    Puyallup, Washington
    No, the ECU reads the signal directly off of the CTS. If you blew the alternator, check into the fuses that are connected to the battery (MPI, etc. etc.) and also check the underhood fuse box. You could've blown one of those.
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  16. 97-gst

    97-gst Proven Member

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    Radford, Virginia


    Its not the excessive cranking thats making it start. i can crank, and crank, and crank but no start. but as soon as i pump the gas it'll fire right up. But i'll check my CTS, fuel presure regulator, and throttle sensor.
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  17. tsi1991awd

    tsi1991awd Proven Member

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    OK, well if you can hit the gas and it'll fire right up, then it isn't your CTS or probably anything fuel related.

    It will most likely be one of the following:

    -Boost Leak
    -ISC
    -TPS

    Because "pumping the gas" is only going to open the butterfly on the throttlebody. It won't do anything for fuel. But in opening the butterfly, it also moves the TPS, which may be adjusted incorrectly. It will also allow extra air into the motor. I say check for boost leaks then check the ISC resistance.
    #17
  18. ranman000

    ranman000 Probationary Member

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    The same thing is happening to me only i was told by the dealer that it was a bad fuel pump, which i replaced, but its still not starting like it should.
    #18
  19. 97-gst

    97-gst Proven Member

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    Radford, Virginia
    yeah when i posted this thread my car had stock fuel mods. Ive since installed a walbro 255, 1050cc injectors and a AFPR and i still have to pump the gas to start my car. It definitely wasn't a boost leak either. I never did get around to replacing my ISC or TPS but idc anymore. Ive kinda gotten used to pumping the gas when i start my car
    #19

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