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Fuel pump question.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 76chevy, Oct 31, 2001.

  1. 76chevy

    76chevy 1/2 ton status

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    This is on a 76 350 4bl Quadrajet. Hot air choke. Eldlebrock intake. Stock cam. Timing chain changed at 72,000 miles. Only 124,000 miles on engine, but old.

    My ride is idling rough and I have checked and set the timing with TDC, all o.k. The rest has been checked also: mixture screws, idle, ignition (new MSD 6A), new fuel filter, new spark plugs, air filter is clean, PCV valve rattles just fine.

    I have had 3 rebuilt carbs from Checker. The first one dumped fuel all over the engine after about 2 weeks and the second was running super rich. It failed emisions even with both idle mixture screws turned in all of the way. I am wondering if these Checker carbs are any good.

    My current carb gets a lot better gas milage but I still run rough. The carb came with the Idle mixture screws 4 full turns out. I have adjusted in using a vacume gauge to get the best vacume.

    Could my problem be my fuel pump? It is about 5 years old and the metal fuel line has been replaced with a 3/8 rubber one. If I feel the fuel line with the truck running I can feel it pumping quite violently. The hose actually moves on it's own. Could it not be providing enough fuel to keep it idling correctly?

    The only other things I can think of are a vacume leak, wich I've tried 3 time to eliminate with no luck even though I don't get any increase in idle when I spray starting fluid or WD40 around the carb or intake. The cam maybe worn since it is the original engine or the timing belt has streched.

    Could it be my Accel wires? I'd like to hope it would be a vacume leak or an adjustment be fore I spent $60 on wires.

    I need to get this thing to pass emmisions soon.


    <font color=red>Spirit of 76</font color=red>
     
  2. Gopherkiller

    Gopherkiller 1/2 ton status

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    Instead of adjusting the mixture screws for the "highest vacume'" try adjusting them for the best idle, and give that a try. Just make sure that you don't have any vacume leaks. You should be able to "stall out" the engine using just the mixture screws, if everything is OK. Use a "light touch," when turning in the screws, you don't want to score them. Probobly have to adjust your idle speed too. No I don't think it's your fuel pump. Good luck! GOPHERKILLER
     
  3. 76chevy

    76chevy 1/2 ton status

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    Thanks for the reply.

    I've tried adjusting for a smooth idle and never get one. I can kill the engine if I turn in both screws. Turning in one almost kills it but not quite.

    I'm going to get new wires because I've heard the MSD wires are much better than the Accel wires. I guess people have had misses they couldn't get rid of until they changed the wires.

    I will check for a vacume leak again. It might be on the upper gasket wich can't spray with my current air cleaner. I've tried to see light through the top gasket with a flash light and haven't seen any.

    I'll also check the ground on the MSD system again.

    <font color=red>Spirit of 76</font color=red>
     
  4. 1986Blazer

    1986Blazer 1/2 ton status

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    Check for vacuum leak from other sources. Check all the hard rubber tubes and soft rubber vacuum hoses. I replaced all of mine a few months ago but I still had a problem, the problem was solved by replacing the PCV valve and replacing the breather hose with a breather cap. I then replaced the wires (I had one that was slightly worn but it was enough for the wire to arc to the exhaust manifold). I also replaced the dist cap and rotor. I doubt the timing chain is bad. My last chain lasted almost 150,000 miles before I replaced it. Just my advice on how I fixed my rough idling.

    <a target="_blank" href=http://www.geocities.com/keywestk5/KeyWestK5.html>http://www.geocities.com/keywestk5/KeyWestK5.html</a>
    So I says to him, I said, "get your own monkey."
    1986 K5, 350 GM Crate, 700R4, NP208
     
  5. Thunder

    Thunder 3/4 ton status

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    It might be your wires. I'v never had too good of luck with Accel wires. They dont seem to last very long before they start leaking voltage. Also make sure none of them are crossed over or wrap around each other. For some reason Accel wires suffer from induction resistance more than other wires.That can cause a miss.

    <a target="_blank" href=http://coloradok5.com/gallery/Thunders-Blaze>http://coloradok5.com/gallery/Thunders-Blaze</a>
    <font color=blue>NEVADA: Where the pavement ends, and the West begins.</font color=blue>
     

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