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bad injectors?

Discussion in 'TBI & EFI Conversions' started by Thejallenator, Feb 18, 2019.

  1. Thejallenator

    Thejallenator Junior Member

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    about 2 weeks ago i went to start up the suburban to leave to work. started it went inside to finish getting ready and came back out to leave. trucks not running. i tried to restart it with no luck, could smell lots of fuel. popped the air cleaner off and notice gas everywhere, on the intake and tbi just flooded. didnt have long to look at it until after work. thought about it while at work and ordered a tbi rebuild kit. i figured either the mani to adapter gasket or adapter to tbi gasket was shot and if im going to tear into it that much might as well rebuild the tbi. both gaskets were well overdue to be replaced, tbi wasnt too bad. hooked everything back up and still no start. at this point it is day time and i can actually see that the tbi above the throttle places is filled with gas and seems to be seeping out onto the manifold. just a mess. seems like its been doiing this a bit. ive been smelling a slight gas smell for a few months.

    ive replaced the coolant sensor, tested the map sensor, tried a different ignition control module, verified i have spark. surely i am overlooking something. the truck has been running fine u to this point, never any starting issues. there is no check engine light. just dumping fuel into the intake!
    1989 r2500 suburban 454 7.3l tbi automatic.
     
  2. bucket

    bucket Super Moderator Staff Member

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    What does the spray pattern look like? It should be a fine mist, spraying in a cone shape.
     
  3. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    Is the fuel coming straight out of the nozzle or seeping around something? Probably not but asking just to be safe.
     
  4. Charlie

    Charlie Mopar by Birth. Chevy by Choice.

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    :welcome:
     
  5. Thejallenator

    Thejallenator Junior Member

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    It is most definitely only coming from injectors in a cone shape. But I wouldnt call it a fine mist. Cranking for roughly 5-7 seconds results in the throttle body filling with about 1/4 to 1/2 inch of gas in it. This is what the spray looks like .
     
  6. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    Woah. Yeah, that’s waaay too much. I have to look carefully to get a good look at mine, but that requires no effort to see it blasting out. I’d like to know what the fuel pressure is and be sure that it has the right injectors, but if everything checked out, I’d see about getting them flow tested somewhere (e.g. WitchHunter Performance). New injectors are expensive, and the only ones that are worth anything are the AC Delcos. Those are my thoughts. I don’t see how it could be anything else... Hmm, the check engine light comes on when you first turn the key?
     
  7. Snoots

    Snoots Supporting Member Supporting Member

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    Holy flooding Batman!
     
  8. Thejallenator

    Thejallenator Junior Member

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    Ive used witchhunter before. Good service. Ill look into that. Its been seeming to run fine the time we've owned it .But at the same time ive only put on around 6-800 miles. The problem just happened out the blue . everything seems normal minus the extra fuel. Cel comes on, fuel pump build pressure in 2-3 seconds.

    How does one check the fuel pressure without buying a 50$ adapter? Assuming these at the stock injectors cause nothing seemed to be touched at all. Couldn't imagine there being something needing injectors bigger than a 7.4 would take.

    Where is the computer located? Just to verify what I'm seeing at the sensors is the same as whats showing up at the ecu. And do the injectors spray more fuel as the engine demands it or just fire at a faster rate? If that makes sense.
     
  9. yevgenievich

    yevgenievich Full Access Member

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    It is pulse controlled, but that might be sticking open and only closing once in a while. Computer is under the passenger side of the dash, behind glove box. Fuel pressure can be checked by getting cheaper adapter that replaces fuel filter during the test
     
  10. bucket

    bucket Super Moderator Staff Member

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    Holy crap!

    This is new territory for me. I've worked on a LOT of TBI engines, but have never seen injectors acting like that before. I'm leaning towards an electronic issue. The reason being, I've never visually seen them kick off and on like that. Normally, they kick on and off so fast that it cannot be seen. When the engine demands more fuel, the "on" time for the injectors becomes greater. To the naked eye, it just looks like a heavier spray.

    I also don't think both injectors would have failed at the same time.
     
  11. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    I was just thinking about this. A noid light test kit would be able to visually demonstrate the injector pulses. You can borrow that at Autozone in addition the pressure test kit. You can backprobe the ECM connector and see what the voltages are for Injectors A (D16)/B (D14). Should be 12 key on, engine off and 14 engine on. You can check injector resistance, should be in the 1.1-1.5 range, low setting. If everything checks out with voltages, resistances, then the injector driver circuit in the ECM can still be screwed up. That covers the electrical part, which if there’s an electrical problem that’s not wiring related, replacing the ECM is your fix.

    8A1CC16A-C1E0-4FF5-93A7-54B3FE707A2A.jpeg
     
    Last edited: Feb 23, 2019
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  12. Thejallenator

    Thejallenator Junior Member

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    I should get the same voltage readings at the injector plugs as at the ecm right? I couldnt get my probes into the plug on the ecm without removing it ..testing at the plugs I didnt see voltage out of the green or blue wires like the diagram shows, but I was getting 11.5ish from the tan and red wires.

    Also when testing the injectors for resistance at first it reads about .3 ohms then works up to 1.1 and bounces around from .9 to 1.2 ohms, hovering in the 1ohm area.

    And lastly is there a buzzer for when the key is in the ignition and door open? I could here a faint buzz when I put the key in and slightly wiggled it. Never heard it before, coming from the speaker in the dash.

    Didn't check fuel pressure yet, its been snowing and I don't want to venture to AutoZone to get the tester.
     
    Last edited: Feb 24, 2019
  13. Thejallenator

    Thejallenator Junior Member

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    6 months later.....
    truck still never started. figured i was having problems with the TBI setup in general but couldn't track down a problem. i ended up getting a holley carb and an HEI distributor. installed these, fairly easy and straight forward. however no matter how hard i tried it seemed that i could never get the thing to even pop off. installed new plugs and wires, verified i had spark everything. i tried im not sure how many times to stab the distributor at #1 TDC but using my timing light it never appeared to be correct (just during cranking) never got it to fire off again. i felt like i was going crazy and couldn't get the timing right, even went as far as to jump the wires one by one around the distributor thinking if i was off doing this would eventually get me into the ball park of where i needed to be. i feel like i've tried just about everything, have the dizzy wired directly to the battery to make sure i had power to it. everything seems like i had it to a point that when i turned the key it should have roared back to life but no. i just get it cranking and cranking a never no pop. :( our house will be listed on the market soon ad i really need to get this thing back on the road, definitely cant make a decent price selling it non running.

    any ideas? or things im possibly looking over????
     
  14. Frankenchevy

    Frankenchevy Supporting Member Supporting Member

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    Is it possible you are 180 degrees out on the dizzy? Perhaps your balancer has spun. How did you verify tdc of #1 on compression stroke?

    Once you’ve found tdc, stab the dizzy at #1, then remember 18436572. If you have spark and fuel it should pop. Even if the valves are a little out.

    Speaking of which, have you checked your timing chain?
     
  15. C10MixMaster

    C10MixMaster Full Access Member

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    switched to a carburetor. How are you getting fuel to the new carb? are you getting fuel to the carb? the fuel pressure from the original in tank pump is to high for a carb and needs a regulator. A quick check for fuel in the carb is to operate the throttle lever while looking in the carb . you should see and hear the accelerator pump shoot fuel in. you said you have spark. Is it a nice blue snap or week? are your plugs wett? frankenchevy is rite if you have fuel and spark you should have fire.. and hes rite about timing chains slipping gm used plastic gears.
     

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