2006 YUKON DENALI XL (6.0L) INTERMITTENT START

Discussion in 'Tech Info' started by YUKONJOSEPPI, Dec 1, 2019.

Car Parts
  1. YUKONJOSEPPI

    YUKONJOSEPPI TYF Newbie

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    HELLO ALL

    I HAVE A INTERESTING PROBLEM ON MY 2006 YUKON DENALI XL (6.0L)

    THE TRUCK HAS A INTERMITTENT START PROBLEM

    THERE IS NO RHYME OR REASON WHEN IT START OR DOES NOT START.

    WHEN IT DOES NOT START ON THE FIRST TIME IT ALWAYS START ON THE SECOND TIME.

    LET ME TELL TELL YOU WHAT I HAVE DONE TO TRY AND FIX IT

    PARTS REPLACE

    (FUEL STUFF)

    -FUEL PUMP TWICE. ONE MOGG AND ONE FROM THE DEALER. THE DEALER TOLD ME THAT THE NEW FUEL PUMP I PUT IN WAS BAD.

    - NYLON FUEL LINE

    -STEEL FUEL LINE CONNECTS TO THE RAIL. ( POINTS OF INTEREST THERE IS NO FUEL FILTER, OR FUEL REGULATOR ON THE RAIL.)

    -INJECTORS

    (ENGINE STUFF)

    -CRANK POSITION SENSOR (THERE IS ONLY ONE CONFIRMED WITH THE DEALER)

    -CAM POSITION SENSOR (DID NOT DO A RELEARN)

    -OIL PRESSURE SENSOR

    -MASS AIR SENSOR

    -MAP SENSOR

    -VAPOR CANISTER PURGE SENSOR (TOP OF INTAKE)

    -ACELERATOR POSITION SENSOR

    -IGNITON SWITCH (DID THE RELEARN FOR PASSLOCK)

    -ALTERNATOR

    -STARTER

    -PCM FLASHED TO THE VIN

    -BODY CONTROL MODULE FLASHED TO THE VIN (DID RELEARN FOR PASSLOCK

    -FUEL TANK PRESSURE SENSOR

    -FUEL RELAY SWAPP

    -FUEL FUEL SWAPP

    WHAT I HAVE DIAGNOSED

    THE FUEL RELAY HAS 4 PINS

    86 30
    87 85

    86 GET 1 VOLT LESS THE BATTERY VOLTAGE WHEN TURNING KEY
    30 GET 12 VOLTS ALL THE TIME
    87 HAVE TO RECHECK BUT I BELIEVE NORMAL 12 VOLTS
    85 I BELIEVE WAS GROUND

    I ADDED NEW GROUNDS TO THE FRAME, CHASSIS AND ENGINE. I CLEANED ALL THE GROUNDS ON THE FRAME AND ENGINE GROUNDS ACCEPT FOR ONE. THE MAIN GROUND OFF THE BATTERY THAT GOES TO THE ENGINE BLOCK.


    WHEN I GO TO START THE TRUCK AND IT DOES NOT START I HAVE THESE TESTER HOOKED UP

    - FUEL GAUGE (50-55 PSI)
    -SPARK TESTER (GETTING SPARK)
    -NOID TESTER (INJECTORS FIRING I CHECKED 2 DIFFERENT ONES

    IF I CYCLE THE KEY 3 TIMES AND TRY IT STILL WILL NOT START

    I WILL TELL YOU THE PRESSURE DOES NOT HOLD AT 50-55 IF I CYCLE THE KEY AND LET IT SIT. ITS LIKE THE CHECK VALVE IS BAD. BUT HOW CAN THAT BE TWO BRAND NEW FUEL PUMPS (ENTIRE HOUSING)

    WHAT CAN I CHECK. SHOULD I BUY A 300-400 COMPUTER AND USE REAL TIME MONITORING TO FIGURE SOMETHING OUT.

    THANKS FOR EVERYONES HELP.

    JOE
     
  2. TheAutumnWind

    TheAutumnWind Full Access Member

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    Turn off caps lock please.

    Does it always turn over when you turn the key and its simply not firing sometimes?
     
  3. YUKONJOSEPPI

    YUKONJOSEPPI TYF Newbie

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    Yes when I turn the key it will always crank. It is 50/50 if the problem will happen. Half the time it starts normal with no problem. There are times when cranking that you can tell it is sputtering and trying to start. This is rare. The normal is

    -turn key cranks but does not start .
    -turn key off
    -try to start again and start every time

    I took it to the dealer twice they told me there is something wrong with the fuse box. Couldn’t tell me the exact problem they just said they saw corrosion. This was not helpful.

    I tested pin 86 and it is giving me a Variety of voltages with the key off. 0.20v - 2.23v. Strange .


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  4. PNW VietVet

    PNW VietVet Full Access Member

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    I would look for a leaking injector bleeding off residual fuel pressure.
     
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  5. YUKONJOSEPPI

    YUKONJOSEPPI TYF Newbie

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    They are all brand new injectors. But I know that doesn’t mean one isn’t bad. What’s the best way to check for that?


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  6. PNW VietVet

    PNW VietVet Full Access Member

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    Sorry, I missed the new injectors but you can still get a bad one that is new. You said this, "I WILL TELL YOU THE PRESSURE DOES NOT HOLD AT 50-55 IF I CYCLE THE KEY AND LET IT SIT. ITS LIKE THE CHECK VALVE IS BAD. BUT HOW CAN THAT BE TWO BRAND NEW FUEL PUMPS (ENTIRE HOUSING)". You are losing pressure and now you have to find out why. You can remove the fuel rail and have the injectors mounted in the rail and then turn the key on and see if you see the pressure build and if any injectors are leaking. Don't crank the engine but just turn the key on.
     
  7. Doubeleive

    Doubeleive Supporting Member

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    I would suspect a leak in the fuel rail, especially if pressure is not holding, I believe there is 3 places for o-rings and there not cheap only the dealer has them. nobody else sells the right size. I would inspect the fuel rail closely at those 0-ring locations use some soap and water spray while cycling the key for fuel pressure leak. just my .02 cents I had a problem with my 00 and bad o-rings in the fuel rail. you might even be able to see a fuel leak if you look close with a flashlight. again just something to check for.
     

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