73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: txchainsawgogi on August 14, 2010, 10:49:35 am
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the truck is hard to start and when it does, it doesn't sound normal anymore...and if I take my foot off the gas it dies. A look under the hood shows that the carbs butterflies will only move by hand...and seem to have a flimsy movement...as if someone retarded rebuilt it and wasn't paying attention when putting it back together. Shouldn't one open when the throttle is engaged?
Keep in mind I haven't been driving this vehicle, last week it ran fine(the best it has) after changing the radiator, thermostat and plugs. Plugs are gapped, boots are tight.
Edit* it magically started just fine, idled just fine and is currently running smoothly. All I did was switch air cleaners...makes zero sense. Carbs are def next to replace after distributor and wires.
Help!
78 C10 350ci
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Sure you're not looking at the choke butterflys?
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Don't replace it, rebuild it. We are talking about a Q-jet, right? Your choke probably needs adjustment, also check your choke pulloff.
http://forum.73-87chevytrucks.com/smforum/index.php?topic=17001.0
You as far as the butterfly not moving, you were probably playing with the air valve. It is not supposed to move until the engine vacuum draws it open under high throttle/high load situations.
http://www.youtube.com/watch?v=nRK9n4NQvOA
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That vid is awesome! QUIT THAT!
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Cool...I may need help rebuilding it. Is there a kit I should be looking for?
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Here's a quality rebuilt kit: http://www.cliffshighperformance.com/carbkits.html
And here is an excellent reference: http://www.amazon.com/Rebuild-Modify-Rochester-Quadrajet-Carburetors/dp/1932494189/ref=sr_1_1?ie=UTF8&s=books&qid=1281933763&sr=8-1
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Oh...I guess my choke pull is loose, those are the parts that feel like they can't be on there right.
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This looks decent...for around the same price as a rebuild kit that is...
What's the round part under the choke?
http://cgi.ebay.com/ebaymotors/Rebuilt-Quadrajet-17059222-79-Chevy-305-350-Carburetor-_W0QQcmdZViewItemQQitemZ330460268835QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories#ht_566wt_941
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You mean the choke pull off?
That's a hot air choke, do you have that or an electric choke?
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Well I guess mine is electric, because I don't have that hot air bit attached to mine... under the choke pull off there is nothing there.
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I want to say a standard quadrajet rebuild kit is like $30. That Cliffs performance rebuild might be worth it but you can get by for much less. Having said that, I'd be a rich man if I had a nickel for every time someone wrongly said their carb. was screwed up and that was the problem with their engine (me included). Maybe its just me but I think your time would be best suited getting to know the adjustments on the carb. and everything related to actually troubleshoot the problem. Buy a carb. off Ebay with no warranty and little knowledge of how to tune one once you install it and you'll likely be frustrated and worse off. You need to go step by step through tuning the one you have before you even know that it isn't in top notch shape but in need of adjustment.
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Maybe its just me but I think your time would be best suited getting to know the adjustments on the carb. and everything related to actually troubleshoot the problem. Buy a carb. off Ebay with no warranty and little knowledge of how to tune one once you install it and you'll likely be frustrated and worse off. You need to go step by step through tuning the one you have before you even know that it isn't in top notch shape but in need of adjustment.
Bingo!
But, if you continue to pursue a rebuild, stick with electric choke. For $99, it's unlikely that is a satisfactory rebuild. If you are looking for a quality rebuilt unit check out SMI (http://www.smicarburetor.com/products/sfID1/28/sfID2/9/sfID3/32), The Carb Shop (http://www.customcarbs.com/carbshopcatalogQjet.htm), or Cliff's (http://www.cliffshighperformance.com/services.html). It's gonna cost you alot more the $99, though.
I want to say a standard quadrajet rebuild kit is like $30. That Cliffs performance rebuild might be worth it but you can get by for much less.
I doubt a $30 rebuilt includes much more than gaskets and a needle/seat assembly. I wouldn't waste my time on a half-effort rebuild. That said, I'm sure there is a better "bang-for-the-buck" rebuild kit out there than the one I posted.
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I've dealt with holley carbs but its been awhile since I've messed with cars. I've been into motorcycles for the past 4 years. I've done rebuilds on those quite a bit.
I'm sure I can do a rebuild myself but I will for sure need help tuning it. Though, couldn't I just buy new jets of the same type and get the carb clean and back to stock?
If I'm not changing yet (dual exhaust, intake manifold) would it even need to be tuned differently? I'm doing away with the emissions stuff, since half of its missing anyway.
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That book I posted earlier contains all the info you need to properly rebuild and calibrate a q-jet.
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You can get that book or I found a step by step adjustment procedure on the web somewhere once. I think my book is a Haynes book from an auto parts store. The adjustments you need to check have nothing to do with jets either. You just need to check the simple stuff like choke adjustment, idle stop screw, fast idle screw, verify choke pulloff operation, spring windup on the secondary airflaps, idle mixture adjustment screws. While you're there check for vacuum leaks and check accelerator pump operation. Since people tend to mess with the choke a lot, it is often the one you'll find all screwed up. It might also be helpful to use a ton of carb. cleaner on every moving part before you start adjusting just to make sure nothing's gummed up and sticking.
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How do I go about fixing the broken/malfunctioning choke pull? Its not electric. When starting it cold, the plate doesn't seem to close all the way.
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You can disconnect the connecting rod to the choke and see if you can close it all the way by hand. If not you might have carbon or something built up on the butterfly flap or where it seats. If you are going to work on the carb. yourself, the book that was listed before is a excellent reference guide with detail pics and breakdowns. I would suggest it be well worth the $20.00 or so to get it, you will more than likely use it several times over the years. Tom
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Do you know how to adjust your choke, or have you tried that yet?
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I'm in Austin as well and been messing with cars for over 20 years if you need any hands on help. :)
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Also be aware that with the engine running, the choke should not be fully closed. If the choke pull off is working correctly, it will pull the choke open a bit with the engine idling.
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I'm in Austin as well and been messing with cars for over 20 years if you need any hands on help. :)
Might not be a bad idea...what part of austin?
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With the engine cold(most of the time) the flap is open a bit...making for hard starting. If I manually push it down the engine fires right up. The connecting rod between it and the choke pull off thing seems too loose. It doesn't have an electric choke.
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I'm in Austin as well and been messing with cars for over 20 years if you need any hands on help. :)
Might not be a bad idea...what part of austin?
Arboretum area.
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Your choke is still operational, though, isn't it (opens all the way when warm). What type of choke do you have? If it's factory and it isn't electric, then it's hot air thermostatic type, which means you can simple loosen the coil cover and rotate it counterclockwise to increase tension on the choke flap (same as adjusting an electric choke). Some coil covers were riveted from the factory, which mean you'll have to remove them first and tap the holes to accept screws. Make note of any adjustments you make by using the tick marks on the aluminum choke housing.
It is unlikely that your choke rod/linkage is to blame. They are always a little loose.