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More Q-Jet questions, float level??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by TrcksR4ME, Jul 26, 2003.

  1. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    I swapped on the q-jet I rebuilt and overall it works fine. I had issues with my new fuel pump where the carb would cut out like it wasn't getting enough gas, no back firing or missing, was like letting off the throttle. I put my old Mallory fuel pump on which is higher pressure, and the problem went away.

    When I took it out wheeling recently the carb would do well down except for uphill under throttle with lots of bumps, would make it if I went slow and easy. The problem was like the one noted above, it would cut out like it wasn't getting enough fuel. It wasn't loading up and stalling, just not getting gas so it seemed.

    Buddy of mine says he thought the float level was probably too low, but I don't know. Anyone have ideas on this matter from my description? And by uphill i mean steep bumpy off road uphill, not uphill on pavement. TIA
     
  2. R72K5

    R72K5 Banned

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    hahve you touched the HEI recently ? sound skinda like lag of power under higher RPM needing timing advancement

    or maybe its just me


    good luck
     
  3. COCHEV

    COCHEV 1/2 ton status

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    did you adjust the float level when you rebuilt it? i think its like 5/16s. q jets can run on like 3 lbs of pressure. i'm sure you did replace the fuel filter on your rebuild?
     
  4. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    Haven't touched anything on the distributer, and it works perfect on the street, I've had it up to 4000rpm's when driving without a problem.
     
  5. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    I didn't adjust the float, which is why i kinda suspect it, and yes it has a new fuel filter.
     
  6. DrMaserati

    DrMaserati Registered Member

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    [ QUOTE ]
    I didn't adjust the float, which is why i kinda suspect it, and yes it has a new fuel filter.

    [/ QUOTE ]

    Why would you "rebuild" a carb and not make the necessary adjustments? Did you make ANY of the adjustments, or just put parts in and slap it back on? Did you put a new float in? If your carb more than about 5 years old it probably needs a new float, which doesn't come in the rebuild kit.

    I suggest you take the carb off and go through it again and make all the required adjustments. With a Q-jet, close isn't usually good enough if you want it to work properly.

    JP
     
  7. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    Although your info is insightful for the "should of done" way to rebuild, I was in a time crunch and tired of waiting on people that were gonna help me with it. I did just slap the new parts in and go, and my question was not how should I have rebuilt it, but what do you think the problem is. And outside of buying the mysterious q-jet book which can only be had by ordereing it online, I could not find every detail to the rebuild process online or here on ck5 for things such as float level.

    And if you read my post, it works great. If I never took it in the dirt I would never know there was a problem, kind of like Holleys and Carters /forums/images/graemlins/rotfl.gif

    So is your answer yes its the float level or no its not, or I dunno what the problem is cause you screwed it up by trying to rebuild it yourself in the first place /forums/images/graemlins/rotfl.gif
     
  8. ji240

    ji240 Registered Member

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    I have rebuilt tons of quadrajets with no problems. I definitley think the float level is a good possibility. Did you put a new float in when rebuilding or use the old one.

    If you used a new one it should definitely be adjusted. If you need help in how to do that exactly let us know. Ill do my best to walk your right through it.

    If you used the old one that is OK too as long as there was no fuel getting inside of it. When you use a new needle and seat that can be enough, depending on the manufacturer, to change the setting from what it was or is suppose to be.

    So in the end, before you go chasing your tail you need to set that correctly. I am assuming you are using the carb that came factory with the truck. If you need any more info please let us know.

    I must also say being new to this board as a steady user that the people here are very friendly, but it is NOT helpful to tell someone what they did wrong and then give no help. make productive use of this great message board and try to help out instead of criticize and walk away.

    Thanks

    John
     
  9. DrMaserati

    DrMaserati Registered Member

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    [ QUOTE ]
    it is NOT helpful to tell someone what they did wrong and then give no help. make productive use of this great message board and try to help out instead of criticize and walk away.

    [/ QUOTE ]

    I assume you're directing this comment at me. If you'll reread my post you will note that I did indeed make a couple of suggestions, namely replace the float if it's old, and make necessary adjustments. All of the specs and instructions on how to do it come in the rebuild kit. Once everything is adjusted to spec, it MAY be possible to diagnose a problem via internet, if a problem still exists. I'm not about to tell him he has a float level problem when nothing has been set to spec, or he may have a 15 year old saturated float, then have to try to explain why I was wrong when that doesn't solve the problem. It may or may not fix the problem.

    It also may depend on whether he's using a 4MV or an M4MC Q-jet. There are differences. Are the accelerator well vent tubes intact, or have one or both fallen out. It's a very common problem. If you've rebuilt "tons of quadrajets" you should know all the little intricacies of them. I've been working on them since the 1960s, so I know a little about them.

    You say you assume he's using "the carb that came factory with the truck." His very first sentence indicates "I swapped on the q-jet," which would indicate otherwise.

    I'm not trying to start an argument here, but perhaps you should read things a little more carefully, and have all your facts straight, before criticizing ME for being critical.

    [ QUOTE ]
    So is your answer yes its the float level or no its not, or I dunno what the problem is cause you screwed it up by trying to rebuild it yourself in the first place

    [/ QUOTE ]

    It MAY be the float level. And no, you didn't screw up by doing it yourself. If you follow the directions in the rebuild kit you should be able to do it just fine, and you'll have a lot more insight into how it works than if you have someone else do it. But if your "time crunch" is past, I suggest you take it back apart, replace the float if it's old, and set everything to spec. I'll bet your problem goes away, whatever it is.

    JP
     
  10. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    Well I don't know much about the q-jets, flying blind here. Kind of jumped in because my old carb was such a POS. The Q-Jet as it stands now works great 95% of the time.

    Lets assume for a minute everything is perfect on it but the float needs to be set properly. (Float is old one by the way) What would be a good place to start? I do not know what spec would be for this application. Instructions with rebuild kit, never had any /forums/images/graemlins/crazy.gif I also am betting that even set to spec it may not perform perfect anyways. But maybe there is a good place to start??

    Like I said before it works perfect except in steep uphill off-road terrain. If I never went on steep off-road rough terrain I would not be posting that I m having problems with it.

    So I would like to assume most the components are working right and try and tweak whatever in order to make it perform better. I just have a hard time believing it is really messed up bad, I drove it like 2-3 hours straight going up a mountain pass , highway cruising, some stop and go, etc on my last wheeling trip with no issues.
     
  11. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    oh, my point...LOL

    If the float was in itself bad, wouldn't it mess up all the time? Same with the rest of the carb, I would think it would have constant problems, but I dunno, thats why I am askin /forums/images/graemlins/1zhelp.gif

    It would seem to me that I am asking more from the carb than maybe it was designed for, but it should work a little better than it is.
     
  12. ji240

    ji240 Registered Member

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    DR. I apologize if my comment was harsh and or critical. It just seemed a harsh statement to start off with, but Im sure I reacted in haste due to other posts I have seen by others. I also do not want an argument and I do not doubt your knowledge of quadrajets. I am familiar with the quirks and intricacies as I am sure many here are. With that said, again, sorry and lets put this behind us and be friends.

    Back to the subject at hand. You should really invest in another kit for the carb and a float. NAPA makes what I feel is a nice kit that will come with instructions. As the good DR stated, with out everything in spec we cant really go any further, and once it is, you should have at least better performance than you have now if not completely fixed. Let us know how you make out when that is done.

    John
     

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