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!HELP! - The Q-JET Nightmare!!!! (** UPDATED 2/14/02 **)

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Greg72, Jan 23, 2002.

  1. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Latest Update (2/14/2002):

    A local mechanic has been swearing at my K5 for the last couple days trying to resolve my "Very Rich Fuel Mixture" issues.......but today he had a "breaktrough"!!!

    The fuel pressure was reading around 8-9psi, which he claims was typical for a big block motor.....but for some reason (and today was the first time he ACTUALLY caught it) the pressure would shoot up to 16psi or higher!!!!! He said he's never seen a mechanical pump do that kind of thing before.

    Of course, this will cause some very disturbing problems no matter WHO's carb is on there....so I am somewhat relieved to find the potential "smoking gun" for this whole issue. I just dropped off my Q-Jet for re-installation, to see if with a new fuel pump & regulator......it will behave the way it's supposed to!!!! [​IMG]

    I'd would like everyone to observe a moment of silence and say a quick prayer that my Q-Jet problems may soon be over....... [​IMG]


    _____________________________________________________________


    Hi guys....the carb is installed now, and I went to do the "Idle A/F Adjustment" procedure. Here's what happened:

    1. Warm up the engine so that the choke isn't active
    2. Set the idle at a reasonable speed (~850RPM)
    3. Turn Idle Mixture screws to change RPM......nothing happens....
    4. Try the other idle screw nothing happens....
    5. Check for a vaccuum leak.....everything is OK
    6. Check distributor timing....currently at 8* BTDC
    7. Hook up gas analyzer to tailpipe......(HC = 600+ppm with idle screws COMPLETELY closed!) GROSS POLLUTER!
    8. Check vaccuum at the carb......almost NO vaccuum signal at all.
    9. Check float levels....appear to match the .300" specification in the manual
    10. Remove carb....base of gasket between the two idle adjustment screws is soaked with fuel.
    11. DOES THIS CARB HAVE A LEAK IN IT'S BASE/CASTING?????

    I'm REALLY lost here guys....my neighbor (who is a mechanic) says I should have like ~50 inches of vaccuum normally.....and I've got next to NONE. The tailpipes are PITCH BLACK from fuel, and the idle screws are completely CLOSED. Floats do not appear to be set too high.....

    Any other ideas why this carb is dumping so much fuel? I'm tempted to think it's just a BAD carb and get a replacement sent right away, unless someone has an idea here.....



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <P ID="edit"><FONT class="small">Edited by Greg72 on 02/14/02 05:04 PM.</FONT></P>
     
  2. arq

    arq 1/2 ton status

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    Re: !HELP! - This new 850 CFM Q-Jet has become a NIGHTMARE!!!!

    what size engine are you running. your carb may be too big for your engine. you shoule be getting around 15-20 of vaccum at idle, 50 is way too much. i don;t think my guage goes that far. if it's under warranty get another one.

    ARQ.

    offroad baja!!!
    72 4x4 CST Blazer
    71 4x4 CST Blazer
    <a target="_blank" href=http://coloradok5.com/gallery/ArqDennis>My Pics</a>
     
  3. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: !HELP! - This new 850 CFM Q-Jet has become a NIGHTMARE!!!!

    Arq,

    It's a 427 Big Block......it seems like it should be OK......The FourWheeler article said it should run on 350 Small Blocks with those small "primaries" and they tested it on their Jeep with a 383 Stroker.

    Man......I hate setbacks....! I just want this thing to WORK! [​IMG]



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  4. jc71355

    jc71355 1/2 ton status

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    Re: !HELP! - This new 850 CFM Q-Jet has become a NIGHTMARE!!!!

    Are you running a heat spacer? I took the carb of my 71 C-10 which was a Q-jet. When i put it on i didn't put the heat spacer back on in between the carb and the gasket. Later on the truck just died on me in the middle of the street. This happened twice until i finally looked and saw gas pouring out under the carb. I just bought a new carb since i had had problems with it before and i couldn't find the spacer. I have since found it at the parts store. Hope this helps

    James

    91K5 350 2.5in Suspension lift 33/12.5
     
  5. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: !HELP! - This new 850 CFM Q-Jet has become a NIGHTMARE!!!!

    James,

    It's sitting on the supplied gasket (about 1/4" thick material) and bolted down onto the manifold.....which is an "Edelbrock Performer 2-0" Dual-Plane in case anyone is interested to know that.

    For what it's worth, the gasket fit perfectly over the hole in the manifold, and all the bolt holes lined up perfectly too.....kinda expect that since it's all Edelbrock though! [​IMG]

    Please keep the ideas coming, or at least tell me that something sounds REALLY wrong with the carb and it's not just my imagination!



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  6. jc71355

    jc71355 1/2 ton status

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    Re: !HELP! - This new 850 CFM Q-Jet has become a NIGHTMARE!!!!

    Just to let you know when i took mine off i had a gasket inbetween the 1/4" spacer or gasket and the manifold. Maybe you just got a dud? I know i got one from holley and eventually went with an Edelbrock Performer. Just thought i'd let you know about the gasket.

    James

    91K5 350 2.5in Suspension lift 33/12.5
     
  7. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: !HELP! - This new 850 CFM Q-Jet has become a NIGHTMARE!!!!

    I'm hoping it's just a "dud"......it's taking way too much effort compared to what I've read....

    "Bolt-it on and GO" was the impression I got.....this has been hours of headscratching so far!

    I ordered a "pre-replacement" Q-Jet from Summit a little while ago. I should have another one by Friday to try out. Maybe there will be some kind of obvious difference in that casting area near the idle jets to CONFIRM that the first one was just BAD....

    I'm never going to get to MOAB at this rate....... [​IMG]



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  8. Twiz

    Twiz 1/2 ton status

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    Re: !HELP! - This \"NEW\" 850 CFM Q-Jet has become a NIGHTMARE!!!!

    850 RPM is a bit too high for idle speed. Idle speed should be around 650-700 RPM with a mild -stock like cam. I would think.

    As the throttle blades open from their seat, the idle speed adj screws will have less and less infulence over the A/F ratio. But at 850 RPMs it should have some influene.

    Gasket soaked with fuel. Hmmm, kinda odd.
    Possibly fuel spilled during removal?
    Possibly, fuel wells leaking? (pretty common on Q-jets)
    Possibly, main-body to throttle plate gasket leaking? (not the carb to manifold gasket, but the one above it on the carb.)

    For the record, don't expect to be able to just bolt on a carb and expect it to run perfectly "right-out-of-the-box". They will need to tweeked and calibrated to perfection.

    <font color=white>.</font color=white>Eric
    <font color=white>.</font color=white>Twizted
     
  9. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: !HELP! - This

    Twiztid,

    Yeah, I was suspicious that maybe the fuel got spilled on that gasket....but it is a very PRECISE area that's soaked, and no trace of fuel anywhere else.

    The RPMs were sometimes lower than 850....but with such low vaccuum it was really "hunting" around and would sometimes just die.

    I wish I had more carb experience to tell you more specifics......unfortunately, I will be a carb expert AFTER all this is completed. [​IMG]

    Thanks for at least validating that I haven't made some gross error on my own......the carb is still suspect in my opinion!



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  10. jc71355

    jc71355 1/2 ton status

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    Re: !HELP! - This

    You said it was hunting... are you running a pvc valve or pcv whichever it is. I disconected mine one time and the engine kept hunting and reving and such. Just another idea. Did you torque the bolts down right? I know mine said to do it criss cross and a certain amount each time. Could this have cracked the body or warpped the bottom?

    91K5 350 2.5in Suspension lift 33/12.5
     
  11. Twiz

    Twiz 1/2 ton status

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    Re: !HELP! - This

    I agree, it sounds like it is extreamy rich. All though, the high H/C reading would indicate possible spark/dead hole or something like that, I can't really tell without seeing all the readings. (C.O., O2, Co2 readings are the main ones to watch for carb adjustments. H.C. is important too, but genneraly related to ignition problems.)

    In the following link (if it works) This pic is of the main body that is up-side-down and the throttle plate removed. You can see the secondarie wells in the center of the pic that have been epoxyed (sealed). Also, above that (top of the pic, out-side the frame, so you can't see it completely) is the Main or Primarie wells, also covered in epoxy, too seal them. Inspect this area on your carb, it might be leaking even if it is new. This is also the area where the gasket is, I was speaking of before.
    <a target="_blank" href=http://community.webshots.com/photo/25820953/25821982iTgIFANmhT>http://community.webshots.com/photo/25820953/25821982iTgIFANmhT</a>

    Hope it helps.

    Someones sig line says:
    "Expiriance is what you get just after you need it the most." -Ain't that the truth!

    <font color=white>.</font color=white>Eric
    <font color=white>.</font color=white>Twizted
     
  12. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: !HELP! - This

    Twiztid,


    EXACTLY!

    The area at the very top of that photo (and partially cut off in the photo) is where they were leaking and soaked the gasket! Those epoxied areas are directly in between the two idle adjustment screws. Of course they're NOT epoxied in mine (and I don't want to risk VOIDing my warranty, so I won't!)

    They were definitely wet....and that's where my neighbor was focusing on. He said it looked unusual to him....and those HC numbers were WAY high.....he had a really cool Snap-On diagnostic machine hooked up with a sniffer in the tailpipe and it gave ALL the standard readings that you get from a smog check. I can't remember the other numbers (O2?, some other specs too)....but he said they all looked wrong.

    BTW -&gt; The PCV was attached during the testing, and it's a brand-new one. (It rattles easily when you shake it....it think that's the "test" for PCV valves!) [​IMG]

    I really appreciate hearing from you.....I have to admit, I'm learning a lot from you guys (and my neighbor) but it's always tough to get this experience "THE HARD WAY".....


    I have to agree: "Experience is something you get AFTER you really needed it!"......truer words were never spoken.




    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  13. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: !HELP! - This

    Oh, by the way here are some cam specs.....just in case you need them:

    <font color=red>Crower "Beast" Hydraulic Cam #01904:</font color=red>

    Grind Lobe Center: 292H 112 degrees
    Advertised Duration:
    Intake: 292
    Exhaust: 302
    Duration at .050":
    Intake: 214
    Exhaust: 224
    Gross Lift 1.7/1.7:
    Intake: .503"
    Exhaust: .529"


    Hope that helps..... [​IMG]



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  14. BurbinOR

    BurbinOR 3/4 ton status

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    Re: !HELP! - This

    Let me ask this - you said the air screws were all the way IN? Or did I read that wrong. If they are bottomed out, they are not allowing ANY air in...........or rather, very small amounts. One side at a time you can adjust the a/f ratio by ear or by vacuum gauge. They need to start backed out about 3 turns (from my foggy memory bank on carbs [​IMG]).

    By the way, the most vacuum you can EVER see is 30"............that is considered a perfect vacuum. Hitting 20 at idle in neutral/park is excellent.

    ONE TON</font color=blue> <font color=green>TPI'd</font color=green><font color=red> BEAST<font color=red>
     
  15. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: !HELP! - This

    BlazinOR,

    The idle mixture screws control the A/F ratio....leaner when turned clockwise (screwed IN) and richer when turned counterclockwise (unscrewing, or OUT).

    My understanding is they only control the amount of fuel being "metered in" to the air. Not the airflow itself....that is controlled with the conventional airscrew near the throttle linkage.

    That's what is so confusing....theoretically, since we screwed those A/F screws ALL the way IN....there was NO fuel to keep the engine running....and yet it continued to puke out black smoke and pegged the hydrocarbons at over 600ppm on the "sniffer".....the fuel was coming from somewhere!!!! ....and obviously the idle mixture screws were having NO effect. The engine RPMs did not rise or fall regardless of how those screws were turned....and the vaccuum was probably at or below 10" most of the time.

    It SMELLED like lots of fuel.....and it certainly seemed to be "loading up"....stumbling....then clearing out again.

    It's all very fishy! [​IMG]



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  16. slider

    slider 1/2 ton status

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    Re: !HELP! - This

    I think you should call Summit or who ever you got it from and have them send you another one. Sounds like that one is foobared. Summit is good about returns. I have never had a hassle with them.
     
  17. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Re: !HELP! - This

    Slider,

    I hope you are right.....I just bought another one from Summit tonight (now I'm at $457.00 x 2) and I'm really hoping that I get a full-refund on the one I am returning.....could you imagine having to "eat" $900 bucks just to get a single working carb?

    OUCH!!!!

    [​IMG]



    -Greg72

    '72 K5 Blazer - 427BB/TH350/NP205/6" Lift/35x12.50's
    <font color=blue>See it here: </font color=blue><a target="_blank" href=http://coloradok5.com/gallery/albun38>http://coloradok5.com/gallery/albun38</a>
     
  18. StageZ

    StageZ Registered Member

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    Re: !HELP! - This

    you would be supprized how much of a friend those guys at edelbrock could be... give them a call... they sent me a free rebuild kit for thier 600 just cause things didnt seem right and I called and asked... sorry this is all the advice i can give you... but give them a call... you might get lucky...
     
  19. Twiz

    Twiz 1/2 ton status

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    Re: !HELP! - This

    BlazzinOR is thinking about a Holley, they adj the A/F ratio in reverse of Q-jets and Carters (edlebrock).

    He is a F.I. guy anyway...what do they know about carbs. [​IMG] J/K

    <font color=white>.</font color=white>Eric
    <font color=white>.</font color=white>Twizted
     
  20. BurbinOR

    BurbinOR 3/4 ton status

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