smog test failure - The 1947 - Present Chevrolet & GMC Truck Message Board Network

hotrodhomi · 10-20-2006, 06:17 PM

My friend’s blazer failed its CA smog test and he wants me to help him fix it. I thought it would be easy but I’m not finding anything obvious. The HC and NO were both within limits, but the CO was real high. Where should we start looking? The blazer is an ’81 with a 305 and the OG quadrajet.

hotrodhomi · 10-20-2006, 10:06 PM

changed the pump shot, the float needle and set the float. he float was way too high and the little clip that holds the float to the needle was missing. Started it up and it smells too rich. How do ou set up the choke at idle? The screw seams to adjust the fuel at idle. Where should this be set so that I can get my baseline? I already set the idle mixtre screws to 2 turns open.

The primary should be straight up and down right? Its not, how do I adjust this? I'm carbarator stupid. Please help.

72C203503ONTHETREE · 10-21-2006, 08:55 AM

The black plastic disc on the passenger side of the carb is where you adjust the choke at. There should be three metal tangs with screws holding them in that hold the plastic disc in position. Loosen up the three screws enough to move the disc. There are arrows and the words "lean' and "rich" on it, turn it towards the "lean" arrows. Not sure what screw youre talking about, only screws I know of are the idle mixture screws and the idle speed screw. When the choke is fully open, the choke butterfly should be perpendicular to the bottom of the carb, like the throttle blades are whenb it is floored. Have you checked his tune up stuff like plugs and wires? A single missfire can cause high CO. A good and cheap way to pass smog is to put a couple cans of alcohol(rubbing, not beer, lol) or Heet in the tank.

hotrodhomi · 10-21-2006, 01:10 PM

Do you know what direction to turn the choke to make it lean? This one doesn't look like its marked.

trixter99 · 10-21-2006, 01:32 PM

You should have to turn it towards the front of the vehicle or clockwise if you are standing on the passenge side looking at the carb .

hotrodhomi · 10-21-2006, 06:09 PM

Thanks, do you know what the adjustment screw below the choke does? Not the idle mixture screw on the base plate, but the screw directly below the choke.

olblue81 · 10-21-2006, 09:11 PM

Quote:

Originally Posted by hotrodhomi

Thanks, do you know what the adjustment screw below the choke does? Not the idle mixture screw on the base plate, but the screw directly below the choke.

High idle speed for when the choke is on.

hotrodhomi · 10-21-2006, 10:30 PM

Quote:

Originally Posted by olblue81

High idle speed for when the choke is on.

How do you adjust this properly?

86swb · 10-22-2006, 11:48 PM

Man I am glad we do not have any kind of checks here. All the smog stuff is no longer on my '86.

hotrodhomi · 10-23-2006, 01:56 AM

anyone know how this should be adjusted?

72C203503ONTHETREE · 10-23-2006, 09:34 AM

Run the engine with it on the high idle, push the choke plate closed then open the throttle with your other hand, that will drop the piece that has the screw on it so it will run on high idle. Keep the plate closed then release the throttle, that will put the choke on as far as the high idle. You may have to put something in the choke horn to keep the engine running if its warm, it will flood out if you dont. Adjust the screw until the high idle speed setting is reached. Not sure what its supposed to be set at, probably 1500 rpm or so.

magnethead · 10-23-2006, 07:07 PM

FWIW my truck is 1800 RPM on high idle

hotrodhomi · 10-28-2006, 12:35 AM

I found a few vacuum lines that were wrong. After I fixed them I sent him back to the smog police. He said the blazer still has high CO values. HC and NO are great. He said the test guy was nice enough to run the tester in manual mode so they could mess with it a little bit. It tested fine at idle and high idle but would fail under load. Why would it fail under load and not at high idle? He said both tests were done at about 1800 RPM. Anyone have any ideas. I'm running out of things to tell him.

petemonster · 10-28-2006, 12:04 PM

i used to take about a gallon of methanol or isoprophyl alchohol and mix it with about 3 gallons of premium gasoline when we had the emissions test in MN.
pure alcohol burns more effeciently than gasoline with less emissions but is highly corrosive to aluminum parts in your fuel pump and carb not to mention the rubber ones.After you have passed the test go filler up to dilute the mixture and you should be fine.
Also replace the PCV valve, breather element air filter,plug wires ,and spark plugs.....I like to use Delco rapid fires....those things I swear by.
The fuel mixing usually works fine but you can replace those parts just to be sure.

hotrodhomi · 10-28-2006, 01:33 PM

Anyone know how to fix the problem. I bet if the problem was fixed it would run better (have more power).

72C203503ONTHETREE · 10-28-2006, 10:46 PM

Reolace all the tune up parts then go from there. Its kind of hard to know whats wrong without seeing the truck in person, lol. Shouldnt cost a lot to replace the cap, rotor, wires, and plugs. If that doesnt fix it theres something goofy going on with the carb or emmissions crap. Sounds like the carb is needing a rebuild or is worn out and running too rich. Get the ignition side good and then mess with the fuel side.

10-20-2006, 06:17 PM	#1
hotrodhomi Registered User Join Date: Apr 2004 Location: Sacramento Posts: 3,737	smog test failure My friend’s blazer failed its CA smog test and he wants me to help him fix it. I thought it would be easy but I’m not finding anything obvious. The HC and NO were both within limits, but the CO was real high. Where should we start looking? The blazer is an ’81 with a 305 and the OG quadrajet. __________________ '72 2wd blazer, bagged w/ watts link & EDC '72 C10 "Lowered Farm Truck" STOLEN 5-18-11 '66 impala ht

10-20-2006, 10:06 PM	#2
hotrodhomi Registered User Join Date: Apr 2004 Location: Sacramento Posts: 3,737	Re: smog test failure changed the pump shot, the float needle and set the float. he float was way too high and the little clip that holds the float to the needle was missing. Started it up and it smells too rich. How do ou set up the choke at idle? The screw seams to adjust the fuel at idle. Where should this be set so that I can get my baseline? I already set the idle mixtre screws to 2 turns open. The primary should be straight up and down right? Its not, how do I adjust this? I'm carbarator stupid. Please help. __________________ '72 2wd blazer, bagged w/ watts link & EDC '72 C10 "Lowered Farm Truck" STOLEN 5-18-11 '66 impala ht

10-21-2006, 08:55 AM	#3
72C203503ONTHETREE Registered User Join Date: Apr 2004 Location: Grant, Alabama Posts: 504	Re: smog test failure The black plastic disc on the passenger side of the carb is where you adjust the choke at. There should be three metal tangs with screws holding them in that hold the plastic disc in position. Loosen up the three screws enough to move the disc. There are arrows and the words "lean' and "rich" on it, turn it towards the "lean" arrows. Not sure what screw youre talking about, only screws I know of are the idle mixture screws and the idle speed screw. When the choke is fully open, the choke butterfly should be perpendicular to the bottom of the carb, like the throttle blades are whenb it is floored. Have you checked his tune up stuff like plugs and wires? A single missfire can cause high CO. A good and cheap way to pass smog is to put a couple cans of alcohol(rubbing, not beer, lol) or Heet in the tank. __________________ 72 Chevy C20, SOLD (Dang it.) 09 Challanger RT six speed in all black. 74 Datsun 710 wagon, all 1.8 liters of screaming Datsun power. 73 C10 long bed, 350/350 combo, nice shape.

10-21-2006, 01:10 PM	#4
hotrodhomi Registered User Join Date: Apr 2004 Location: Sacramento Posts: 3,737	Re: smog test failure Do you know what direction to turn the choke to make it lean? This one doesn't look like its marked. __________________ '72 2wd blazer, bagged w/ watts link & EDC '72 C10 "Lowered Farm Truck" STOLEN 5-18-11 '66 impala ht

10-21-2006, 01:32 PM	#5
trixter99 I have no time for this Join Date: Dec 2002 Location: Fort St John B.C. CANADA Posts: 434	Re: smog test failure You should have to turn it towards the front of the vehicle or clockwise if you are standing on the passenge side looking at the carb . __________________ 1986 Chevy short box ( PROJECT ) 1994 Chevy Blazer lifted 6" 2009 Gmc 2500 HD 1999 Hugger orange Camaro SS 2007 BMW X5 Sport

10-21-2006, 06:09 PM	#6
hotrodhomi Registered User Join Date: Apr 2004 Location: Sacramento Posts: 3,737	Re: smog test failure Thanks, do you know what the adjustment screw below the choke does? Not the idle mixture screw on the base plate, but the screw directly below the choke. __________________ '72 2wd blazer, bagged w/ watts link & EDC '72 C10 "Lowered Farm Truck" STOLEN 5-18-11 '66 impala ht

10-22-2006, 11:48 PM	#9
86swb Born a Chevy Man Join Date: Apr 2005 Location: Navarre, Florida Posts: 10,221	Re: smog test failure Man I am glad we do not have any kind of checks here. All the smog stuff is no longer on my '86. __________________ John or 86 (Viet Nam combat Vet-BIG RED ONE) '65-'66 1986 Chevy SWB Silverado 1984 Chevy Longbed Silverado New Kia Sportage (Wife's car and she loves it) CHEVY, American made w/pride! If you can read this, YOU NEED TO THANK A TEACHER! If you can read this in ENGLISH, PLEASE THANK A SOLDIER! GOD BLESS AMERICA AND BLESS OUR FIGHTING TROOPS

10-23-2006, 01:56 AM	#10
hotrodhomi Registered User Join Date: Apr 2004 Location: Sacramento Posts: 3,737	Re: smog test failure anyone know how this should be adjusted? __________________ '72 2wd blazer, bagged w/ watts link & EDC '72 C10 "Lowered Farm Truck" STOLEN 5-18-11 '66 impala ht

10-23-2006, 09:34 AM	#11
72C203503ONTHETREE Registered User Join Date: Apr 2004 Location: Grant, Alabama Posts: 504	Re: smog test failure Run the engine with it on the high idle, push the choke plate closed then open the throttle with your other hand, that will drop the piece that has the screw on it so it will run on high idle. Keep the plate closed then release the throttle, that will put the choke on as far as the high idle. You may have to put something in the choke horn to keep the engine running if its warm, it will flood out if you dont. Adjust the screw until the high idle speed setting is reached. Not sure what its supposed to be set at, probably 1500 rpm or so. __________________ 72 Chevy C20, SOLD (Dang it.) 09 Challanger RT six speed in all black. 74 Datsun 710 wagon, all 1.8 liters of screaming Datsun power. 73 C10 long bed, 350/350 combo, nice shape.

10-23-2006, 07:07 PM	#12
magnethead 7000 #'s of american IRON Join Date: Dec 2004 Location: north tx Posts: 883	Re: smog test failure FWIW my truck is 1800 RPM on high idle

10-28-2006, 12:35 AM	#13
hotrodhomi Registered User Join Date: Apr 2004 Location: Sacramento Posts: 3,737	Re: smog test failure I found a few vacuum lines that were wrong. After I fixed them I sent him back to the smog police. He said the blazer still has high CO values. HC and NO are great. He said the test guy was nice enough to run the tester in manual mode so they could mess with it a little bit. It tested fine at idle and high idle but would fail under load. Why would it fail under load and not at high idle? He said both tests were done at about 1800 RPM. Anyone have any ideas. I'm running out of things to tell him. __________________ '72 2wd blazer, bagged w/ watts link & EDC '72 C10 "Lowered Farm Truck" STOLEN 5-18-11 '66 impala ht

10-28-2006, 12:04 PM	#14
petemonster Registered User Join Date: Oct 2006 Location: minnesota Posts: 5	Re: smog test failure i used to take about a gallon of methanol or isoprophyl alchohol and mix it with about 3 gallons of premium gasoline when we had the emissions test in MN. pure alcohol burns more effeciently than gasoline with less emissions but is highly corrosive to aluminum parts in your fuel pump and carb not to mention the rubber ones.After you have passed the test go filler up to dilute the mixture and you should be fine. Also replace the PCV valve, breather element air filter,plug wires ,and spark plugs.....I like to use Delco rapid fires....those things I swear by. The fuel mixing usually works fine but you can replace those parts just to be sure.

10-28-2006, 01:33 PM	#15
hotrodhomi Registered User Join Date: Apr 2004 Location: Sacramento Posts: 3,737	Re: smog test failure Anyone know how to fix the problem. I bet if the problem was fixed it would run better (have more power). __________________ '72 2wd blazer, bagged w/ watts link & EDC '72 C10 "Lowered Farm Truck" STOLEN 5-18-11 '66 impala ht

10-28-2006, 10:46 PM	#16
72C203503ONTHETREE Registered User Join Date: Apr 2004 Location: Grant, Alabama Posts: 504	Re: smog test failure Reolace all the tune up parts then go from there. Its kind of hard to know whats wrong without seeing the truck in person, lol. Shouldnt cost a lot to replace the cap, rotor, wires, and plugs. If that doesnt fix it theres something goofy going on with the carb or emmissions crap. Sounds like the carb is needing a rebuild or is worn out and running too rich. Get the ignition side good and then mess with the fuel side. __________________ 72 Chevy C20, SOLD (Dang it.) 09 Challanger RT six speed in all black. 74 Datsun 710 wagon, all 1.8 liters of screaming Datsun power. 73 C10 long bed, 350/350 combo, nice shape.



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