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no power @ low rpm's

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by bigdaddy89, May 9, 2001.

  1. bigdaddy89

    bigdaddy89 1/2 ton status

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    no power @ low rpm\'s

    For some reason I am not getting much power at low rpm's. Once it gets to higher rpm's it gets the power back, as if it was resticted some how for a moment. I have been chasing this problem for about a month now, but can't figure out what the problem is. So far I have checked all of the plugs, wires, cap, and rotor with no signs of any problems. I took out my Hypertech chip and replaced it with the original and it seemed to help a little. At this point I thought it might be a fuel or air mixture problem so I checked the injectors and one of them looked like it wasn't spraying as much as it should, so I took apart the entire tbi system and cleaned everything, plus replaced the injector. Now it ran a little better. I checked the amps going to the fuel pump and it was ok, so it can't be the pump. I have also changed the fuel filter. Does anybody have any ideas? This is an 89 350fi w/AT.

    GOT ROCKS?
     
  2. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    Re: no power @ low rpm\'s

    Have you checked the timing? Mine is carburated but after a recent rebuild the timing slipped back to almost 0 tdc and I had lost alot of low ranger power
    Brent
     
  3. AZK5

    AZK5 1/2 ton status

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    Re: no power @ low rpm\'s

    Is this a new problem or one that has existed since the tire change? What gears are you running? [​IMG]
    CB
     
  4. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: no power @ low rpm\'s

    I Promise it is the pump. Change the thing and your truck will be spinning the tires again off the line... I had an 88 EFI, and it went thru 3 fuel pumps. Everytime, the truck would start to lag off the line, and then it would come-to once about half-way thru the RPM range.

    The pump is cheap anyhow, you can't lose, expecially after all the time you have spent looking for the answer. This wouldn't be the first time I was right on things like this...

    JUST MY .02...

    <font color=red> Check out my truck @ </font color=red>
    <A target="_blank" HREF=http://24.10.209.54/bigolk5.htm>http://24.10.209.54/bigolk5.htm</A> [​IMG]
     
  5. Executioner

    Executioner 1/2 ton status

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    Re: no power @ low rpm\'s

    He say's he checked the pump Amperes, and its ok.
    Anit no way to chech a feul pump to me.
    Sound like the low tech approach, is not working. Its gona cost you to really test the fuel pump
    invest in a fuel pressure, and fuel volume tester($$$$$$$$$$$$$$$$$).
    Good luck
     
  6. bigdaddy89

    bigdaddy89 1/2 ton status

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    Re: no power @ low rpm\'s

    Well I guess I will be changing out the pump. This problem started months after the tire change, so it can't be that. I was told by a GM tech that if the fuel pump is drawing more than 3 amps than it is bad. I know some people have cut out the floor to do this replacement. Do you just cover it back up with a donor floor board, or is there an easier way? Give me some ideas on this one please.

    GOT ROCKS?
     
  7. CaptCrunch

    CaptCrunch 1/2 ton status

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    Re: no power @ low rpm\'s

    You need to check the fuel pressure... not the amps going into the pump. It should be between 11 and 13 psi. Double checking the timing is also a good idea... make sure you unplug your adv wire. Last resort would be to start compression testing to see if you have a bad cylinder or possible a bad valve, etc. Good Luck

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  8. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    Re: no power @ low rpm\'s

    Drop the tank and put in the 31 gallon tank..... Don't cut the hole.
    My pump failed due to shattered baffle/bucket. I bought a new tank (26 gal cuz I didn't know about the 31 - DOH!) and new pump and all is well.
    Simple cheap test - while engine running, screwdriver to tank, ear to screwdriver (plastic end is safer) - if
    it doesn't sound like an angry beehive your pump is bad. The new pump will be audible from quite a distance also. That was my biggest surprise. Dave
     
  9. Dirteater

    Dirteater Newbie

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    Re: no power @ low rpm\'s

    After tearing apart my TBI to replace it with an after market FI system I found the port on the TBI body going to the MAP sensor was plugged with a hard substance. If I'd of only known. The Pro-Jection 4-D is almost in and I hope it rocks.
    Try using a vaccum tester on all of your vaccum ports. If one is clogged you will get horrible response off the line, I did.
     
  10. bigdaddy89

    bigdaddy89 1/2 ton status

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    Re: no power @ low rpm\'s

    I am going to give the screwdriver test a try. I will even use my good ear. I haven't tried any of the vacuum lines for blockage, sounds like a good idea. Thanks guys for all the help.

    GOT ROCKS?
     
  11. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Re: no power @ low rpm\'s

    DAMN! You are trying to tell me you know someone who cut a hole in the floor of their truck to change the fuel pump??!!!! Someone take that guys license!

    GM was nice enough to suspend the tank with 2 straps that you can unbolt to drop the tank. My only suggestion is that you wait to do this until you have no more than 1/4 tank of gas. That 33 gal. tank gets pretty heavy!!! [​IMG]

    Pull those two straps and the tank drops into your lap. Then use a screw driver and a small hammer to turn the locking mechanism around where all the fuel lines exit the tank. You will notice it's keyed, and will release once you turn it far enough.

    Last, make sure you replace the "sock". This is a rectangle shaped nylon sock that acts as a filter before the fuel pump. The first one I replaced was so old it was brittle and just fell apart in my hands!

    Have fun! AND FOR THE LOVE OF GOD - DON'T CHOP ANY HOLES IN YOUR TRUCK OK?

    [​IMG]

    <font color=red> Check out my truck @ </font color=red>
    <A target="_blank" HREF=http://24.10.209.54/bigolk5.htm>http://24.10.209.54/bigolk5.htm</A> [​IMG]
     

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