Gas? Air? Mixture?!? HELP!! lol

	Blazer Forum Classifieds Photo Gallery Search Contact BF Sponsors
Blazer News Member List Forum FAQ Timeslips Recalls TSBs Calendars Register Login

Gas? Air? Mixture?!? HELP!! lol

Printable Version

Blazer Forum >> Mechanical & Maintenance >> General Tech Help >> Full Size Tech >> Gas? Air? Mixture?!? HELP!! lol

Page: [1]

Message

<< Older Topic Newer Topic >>

Gas? Air? Mixture?!? HELP!! lol - 4/6/2008 9:13:46 PM

drewski120

Posts: 15
Joined: 3/31/2008
Status: offline

OK the 1974 K5 blazer, 383, RV cam, flathead pistons, new ignition system(coil, distributor, and plugs/plug wires), and a 600 CFM Carter AFB performance series carburetor...

Problem im having is starting, when i pump the gas pretty good it WILL turn over, but unless i keep just the exact right amount of pressure on the gas pedal it will do one of two things...backfire loudly(which includes fire exiting thru the carburetor, NOT GOOD im guessing)...is this a mixture issue or what?

Is there a troubleshooter i need to follow or what? lol

Thanks for the help

_____________________________

Andrew

Post #: 1

RE: Gas? Air? Mixture?!? HELP!! lol - 4/6/2008 11:38:18 PM

BigBlack73

Posts: 43
Joined: 3/12/2008
Status: offline

the backfire would most likely be from the carb gettin loaded up a bit. i would say your gettin to much air to your carb, considering you have to give it an equal amount of gas to go with air for it to start. almost like the carb isn't choked enough when first starting it. if it's automatic choke, then your getting the correct amount of air, your probably just getting not enough gas. which could mean your idle is set too low, or your fuel pump is gettin worn out. if it's manual choke, make sure it's choked enough when starting it. if none of this has made any difference, i would, as said before, mess with the idle a bit and see what happens. shoulda got a edelbrock 1400 series ;) lol.

_____________________________

1973 K5 Blazer
SB350 + 1405 Edelbrock
SM465 + NP205
Inverted leaf springs on 4" blocks
38.5 Swampers

(in reply to drewski120)

Post #: 2

RE: Gas? Air? Mixture?!? HELP!! lol - 4/7/2008 4:31:36 AM

swartlkk

Posts: 14299
Joined: 5/1/2005
From: Waterloo, NY
Status: offline

I would venture a guess that this has to do with your timing post as well. Intake backfires can be caused by having the spark too advanced.

If you are having to hold the throttle open a bit, I would have to wonder what your choke fast idle is set at and if it is proper. You may have to pump the carb a bit to get some fuel into the intake, but you shouldn't have to hold the throttle 'just right' to get it to start after that.

_____________________________

Kyle-

2004 Rainier
1970 Chevelle - Resto
1974 K5 Blazer - Resto

(in reply to BigBlack73)

Post #: 3

RE: Gas? Air? Mixture?!? HELP!! lol - 4/7/2008 1:52:05 PM

drewski120

Posts: 15
Joined: 3/31/2008
Status: offline

It is a manual choke, gonna try some of the stuff mentioned and will post back...lemme know if you think of anything else please.

Thank You

_____________________________

Andrew

(in reply to swartlkk)

Post #: 4

RE: Gas? Air? Mixture?!? HELP!! lol - 4/7/2008 9:12:40 PM

drewski120

Posts: 15
Joined: 3/31/2008
Status: offline

Ok so i tinkered with it for HOURS today...i put the two adjustment screws on the front alllll the way in and tried to start it and then just slowly took the screws out half a turn at a time trying to get it adjusted but i just cant get this thing to stay running...i was going to adjust the idle but this carb has the wierdest throtle cable in the world and i cant figure out how to adjust the idle...urghhhh headache..

(in reply to drewski120)

Post #: 5

RE: Gas? Air? Mixture?!? HELP!! lol - 4/7/2008 9:22:33 PM

swartlkk

Posts: 14299
Joined: 5/1/2005
From: Waterloo, NY
Status: offline

THIS link may help... All I could find short of buying a book on the Carter AFB carbs.

_____________________________

Kyle-

2004 Rainier
1970 Chevelle - Resto
1974 K5 Blazer - Resto

(in reply to drewski120)

Post #: 6

RE: Gas? Air? Mixture?!? HELP!! lol - 4/7/2008 9:29:23 PM

drewski120

Posts: 15
Joined: 3/31/2008
Status: offline

Hmmm thanks Kyle, really appriciate the help...dunno what im gonna do yes but ill just keep tryin i guess.

_____________________________

Andrew

(in reply to swartlkk)

Post #: 7

RE: Gas? Air? Mixture?!? HELP!! lol - 4/7/2008 10:13:25 PM

BigBlack73

Posts: 43
Joined: 3/12/2008
Status: offline

Damn... sorrry man, if anything else pops into my head i'll definitely let ya know. i'm not familiar with carter carbs at all.

_____________________________

1973 K5 Blazer
SB350 + 1405 Edelbrock
SM465 + NP205
Inverted leaf springs on 4" blocks
38.5 Swampers

(in reply to drewski120)

Post #: 8

RE: Gas? Air? Mixture?!? HELP!! lol - 4/7/2008 10:24:44 PM

Chevy Lover

General Tech Moderator
Posts: 3411
Joined: 6/11/2006
From: Vancouver. B.C. Canada
Status: offline

I just checked the link that swartlkk sent you and I would have given similar answers as #3 & #4.

_____________________________

Give a man a fish and he will eat for a day, teach a man to fish, and he will sit on a boat drinking beer for a life time

(in reply to BigBlack73)

Post #: 9

RE: Gas? Air? Mixture?!? HELP!! lol - 4/8/2008 6:55:21 AM

drewski120

Posts: 15
Joined: 3/31/2008
Status: offline

The biggest problem i'm having right now is the truck wont even run at idle...so i cant adjust the carb at all with knowledge of how the engine is running at each setting...so its all guess work really...I've considered a new carb but i really dont have the money for all that right now, one thing i noticed thats odd to me and once again makes me think its gottttta be a idle adjustment...if i get it to turn over and hit it hard on the gas, talkin like 2000 rpms, it will stay going(doesnt really have a choice right? lol) but that just does not seem right at all...but granted im a 17 y/o self-taught mechanic here so my skills/experience, is very limited...thanks again for all your helps guys.

_____________________________

Andrew

(in reply to Chevy Lover)

Post #: 10

RE: Gas? Air? Mixture?!? HELP!! lol - 4/8/2008 9:23:41 AM

swartlkk

Posts: 14299
Joined: 5/1/2005
From: Waterloo, NY
Status: offline

Base settings on most carbs are 1.5 turns on the mixture screws on the front and screw the idle speed screw all the way in (fastest idle). This should get you running. If not, try playing with the timing by rotating the distributor and see how that affects things.

_____________________________

Kyle-

2004 Rainier
1970 Chevelle - Resto
1974 K5 Blazer - Resto

(in reply to drewski120)

Post #: 11

RE: Gas? Air? Mixture?!? HELP!! lol - 4/8/2008 1:22:56 PM

drewski120

Posts: 15
Joined: 3/31/2008
Status: offline

OK got her to run, thanks everyone for the help, especially Kyle on that last post, i was adjusting the wrong screw for idle which explained SOOOO much(i felt really stupid)...anyway now i've got a loud squel/squeak from under the hood(I mean realllllly loud too) checked oil, its good, so im thinking its the belts, concur? disagree?

Thanks again!

(in reply to swartlkk)

Post #: 12

RE: Gas? Air? Mixture?!? HELP!! lol - 4/8/2008 1:35:56 PM

swartlkk

Posts: 14299
Joined: 5/1/2005
From: Waterloo, NY
Status: offline

Remove the belts and see... For testing purposes on a cold engine, the belts are not necessary.

_____________________________

Kyle-

2004 Rainier
1970 Chevelle - Resto
1974 K5 Blazer - Resto

(in reply to drewski120)

Post #: 13

RE: Gas? Air? Mixture?!? HELP!! lol - 4/8/2008 2:54:19 PM

drewski120

Posts: 15
Joined: 3/31/2008
Status: offline

K its not the belts...the squel SEEMS to be coming from the carburetor or carb area...

(in reply to swartlkk)

Post #: 14

RE: Gas? Air? Mixture?!? HELP!! lol - 4/8/2008 3:10:10 PM

swartlkk

Posts: 14299
Joined: 5/1/2005
From: Waterloo, NY
Status: offline

Is it a cyclic squeak sound or is it more like a whistle?

_____________________________

Kyle-

2004 Rainier
1970 Chevelle - Resto
1974 K5 Blazer - Resto

(in reply to drewski120)

Post #: 15

RE: Gas? Air? Mixture?!? HELP!! lol - 4/8/2008 3:12:00 PM

drewski120

Posts: 15
Joined: 3/31/2008
Status: offline

Well...i would say more like cyclical but it just randomly started doing this so im not really sure...friend says it sounds just like a pig squealin lol

< Message edited by drewski120 -- 4/8/2008 3:44:20 PM >

(in reply to swartlkk)

Post #: 16

RE: Gas? Air? Mixture?!? HELP!! lol - 4/12/2008 7:25:24 AM

drewski120

Posts: 15
Joined: 3/31/2008
Status: offline

Ok so i finally got her to start...now im hearing a LOUD squeal from the engine compartment(can be heard in the cab)...I checked the belts, its not them...a friend says its coming from the carburetor, which it could be but thats odd no? Well any tips or advice would be appriciated

1974 K5 Blazer, 383 stroker, new ignition system, Carter AFB 600 CFM 4-barrel carb.

_____________________________

Andrew

(in reply to drewski120)

Post #: 17

RE: Gas? Air? Mixture?!? HELP!! lol - 4/12/2008 7:31:32 AM

swartlkk

Posts: 14299
Joined: 5/1/2005
From: Waterloo, NY
Status: offline

Can you narrow down where it is coming from? The only sound that would be cyclic would have to come from the rotating assembly (NOT GOOD) if the accessory drive belts are off.

Without a better description, it is VERY difficult for any of us to pin point the problem for you. We depend on your description to diagnose the problem. You really need to go over the engine with a long screw driver, handle to your ear, other end touching on various components of the engine while its running, trying to find a location that has the noise you describe.

_____________________________

Kyle-

2004 Rainier
1970 Chevelle - Resto
1974 K5 Blazer - Resto

(in reply to drewski120)

Post #: 18