1993 5.7 TBI - Injectors dumping too much gas.

Discussion in 'Chevy Truck Forum' started by c15004ever, Apr 28, 2011.

  1. c15004ever

    c15004ever Senior Member

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    '93 tbi 5.7 Feel like im just talking to myself in the other post and I wanted
    to start a new one since I have narrowed down my fuel consumption problem.

    My fuel injectors have been dumping waay too much gas at idle and
    throughout driving causing horrible fuel mileage.
    I have taken apart my throttle body and replaced the fuel pressure regulator diaphram;
    the injectors look spotless.
    After this my spray seems a bit more normal as in it fires in bursts now instead of
    the constant stream it had been doing, but it still seems like it is spraying too much gas.

    Im thinking it is either the injectors themselves or the ecm; could it be the prom?
     
    Last edited by a moderator: Apr 28, 2011
  2. crabtruck

    crabtruck Senior Member

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    Spraying from injectors is a good thing, clean is good too.
    But weeping or leaking is not a good thing (according to Martha :))

    You need to check why they are behaving like this, I would think
    that if both suddenly started acting like this, it's not the injectors themselves.
    Putting a node tester or such on injector terminals would help
    see if signals are being sent properly.
    Might also want to see if disconnecting them one by one
    so that they each get a turn stops the leak effect. Might be a short
    of low effect causing the injectors to stay a little bit on
    It does happen that wires get pinched and damaged under the aircleaner
    causing shorts to each other or to ground, which is the control method.
    Inspect the wires carefully for evidence of that.

    And yeah, I know the talking-to-yourself effect, but hang in there,
    everybody is on their own unscheduled schedules. :)
     
  3. c15004ever

    c15004ever Senior Member

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    What kind of tester do I need for the injectors, can i get them scanned somewhere without having to pay a bunch? They have started acting up all at once and some overconfident guy at an auto parts store said get new injectors...I wonder why a sales representative wants me to buy two $75 injectors hmmm. I noticed that the white wire for the right injector looks like it has been pressed down on and crushed, but it still looks reasonably intact.Also gotta make a 20 mile trip to town because i broke one of the **** bolts holding on the regulator; ahh its the little things that make the spice of life.
     
  4. zombie1969

    zombie1969 Senior Member

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    Checking fuel pressure would be good because if somehow the return line is restricted it would be too high and cause it to run rich.The map sensor malfuntioning would.The temp sensor and the 02 also.
     
  5. c15004ever

    c15004ever Senior Member

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    I need to get the fuel pressure tested when I get some money, gotta love this economy. I have a fairly new holley map sensor, both cts are new, and o2 sensor is brand new.
     
  6. crabtruck

    crabtruck Senior Member

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    So did you try it with one inj unplugged to see if still weeping ?

    Testers used to be made by Kent-Moore for GM
    and had a part number of J-24642-F(several versions nothing-to-F)
    or part number BT-7220-1. Used to be able to order from them
    or Sun Electric Corp. Believe SnapOn bought Sun in 1992.
    SnapOn has something for $50 that handles many domestic ignitions.
    YA2700, Tester, Ignition Module
    Pricey for a set of blinking lights because you don't so much
    measure them, as much as look to see they ARE blinking.
    I'd go ebay, looking for less than $20, right now I've seen at $40
    ignition module tester | eBay=
     

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  7. c15004ever

    c15004ever Senior Member

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    no, i havent tried unplugging one yet i may try it later today. After rebuilding that regulator my mpg seems better, but i need to drive it more to know for sure; gonna make the 50 mile drive to work tonight so i will know for sure if my mpg is any better. After buying the regulator diaphram and a tank of gas I have no money left over now, but as soon as i get some i will rent a tester for my injectors from an auto store and check them out. Do I unplug the injector before i crank it or does it matter?
     
  8. crabtruck

    crabtruck Senior Member

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    Lost on time-line a little, have you seen weeping / leaking after reg swap ?
    There should be no fuel or drip if both are unplugged.

    The injector is getting a 'ground' signal on that wire from ECU,
    the other half of 2-wire plug is battery voltage from key,
    I would not unplug while cranking/running to avoid arcing damage.
    It's only a split second of on time, but can be as high as 9A.
    That's if ECU goes near real ground across those 1.3 ohm injectors.
     

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