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  1. #1

    Default 1991 K1500 4x4 pick-up with Bizare problem??? Assistance needed please.

    Back history: I have owned this 1991 for the past 8 years. Before that, it was owned by my father in law who was a mechanic. The truck has 175K on it. Regularly maintained.

    The current issue stared on Thursday. At lunch, I was late for work. Running low on gas, but was late, so I thought I would fuel up when I get out.

    I came around a street corner, on a downhill, the fuel sloshed in the tank, and it momentarly cut out.

    After work, it fired right up, and I drove straight to the closest gas station. It was a run down Arco i never use because I worry about the condition of their tanks.

    Filled up all the way and headed home, a 12 mile trip. About half way there, it started to cut out when I let off the gas. Died a couple of times around corners, but I got it home.

    The following morning, I started the diagnosis. Now the truck would not idle by itself. When you let off, it died. It progressively got worse too. I would turn over but not catch. Then it would run, but it would die all of a sudden as if it ran out of fuel. Always had spark.

    I started to think either fuel filter,fuel pump or water in gas. So I dropped the gas tank. Emptied it completely (it look good in there, no sediment). While I had the tank out, I decided to put a new Napa Gold Bosch pump, new tank hoses and new fuel filter.

    Put it back all together, checked for leaks and turned it over a couple of times. I finally caught and ran for 5 minutes. Would not idle again. Then it died under 1/4 throttle as before. Felt like it was out of fuel.

    It would not start back up. Let it cool off for a while, and it started up again. Then died the same way, under throttle as before.

    Checked the new pump. Primes for 2s. Then reprimes after cranking. A lot of fuel gets pumped (I checked my breaking the line at the fuel filter and cranking).

    Pulled the plugs all along one side, all have spark. Poured a capfull of fuel into the TB (TBI model), it caught for a sec, burned up the fuel and died again. Tried that twice more, with same result.

    Used paperclip to pull codes. Only 12 (which means nothing I believe, just that you are in diagnostic mode).

    Like I said, it feels like it runs out of fuel. And the TBI injectors seem dry, until it catches the next time again.

    What shut off the fuel to the TBI injectors?

    Please help.

    Thank you
    Last edited by mk23; 01-22-2011 at 09:18 PM.

  2. #2
    Sr. Mechanic
    kburb's Avatar
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    Default

    There are a couple of filters in the injectors that may be clogged, pull the regulator might have trash in it, might also have trash in the supply line. All of these are kinda long shots but gives you start. Autozone has a breakdown of the TBI unt on their web site that can help also.

    Good luck and keep posting with results.



    91 Suburban

    D44/14BFF w/Disc conv - Yukon 4:88's - Yukon Grizzly Lockers F/R -13" lift - DIY4x Shackle Flip - 37 ATZ on 18 MT Classics - Doug Thorley headers - Magnaflow - Holley Pro Jection Intake - Ultimate TBI mods - Hydroboost Brake Conversion - Hysteer-X Over Conversion.

    (Coming up - Fuel Injected 383 Stroker - Divorced NP205 - D60 - 40" tires)

  3. #3
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    stephan's Avatar
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    X2 on Kburbs post. I don't believe in coincidence so this has to be associated with the fuel you got from the questionable tanks. If you don't find any dirt (which you may not since you said your tank was clean inside) I would look for water in your lines. Water is heavier than gas, so when you filled up it would settle to the bottom of the tank & you would fill your lines with it first. Blow out your lines completely, & get some fresh gas. Let the other gas sit & the water will settle out & you can carefully pour off the gas from the top so it doesn't go to waste.
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol


  4. #4

    Default

    I have an update.

    We made some progress today.

    I got a fuel pressure gauge and some noids.

    The fuel pressure is right at 13 psi. When first on, it goes up to 13 for a couple of seconds.

    If you don't turn it over right away, it peters off.

    But it goes right back to 13 psi when you crank.

    Tried the noids. No lights when cranking.

    Followed the charts in the shop manual, and diagnosed a Ignition module as Non functioning.

    I bought an ignition module form Napa today (the nicer Echlan brand one) and put it in.

    Now she fires right up, and races nicely.

    But when you let it come down back to where idle should be, it dies.

    Starts right back up, but dies if you try to idle it.

    Both injectors are spraying nice conical patterns.

    But you can see they stop spraying fuel completely if you try to let it idle.

    They don't dribble off, they just flat stop.

    Any ideas? What would be shutting off the fuel?

    Also, is there something I should be looking at that would have burned up and ignition module?

    Thank you for all the help so far guys!

  5. #5

    Default

    Sounds almost exactly as the same problem I'm having with my 93. I haven't figured it out yet.

  6. #6

    Default

    It ended up being my distributor.

    The pole pieces were rusting out, and the computer couldn't figure out proper timing.

    I put in a freshly rebuilt Delco unit from Amazon, and now she runs smooth!

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