Carb Trouble, Need Help Please

[NathanE]

I have a 1974 Chevy C10 that I purchased from someone who obviously did not care for the vehicle in the last 5 years. Recently I performed some work on the suspension, and have moved to the engine compartment. I am by no means a trained mechanic and have come across a stumbling block I was hoping to get help with.

Description of issue:
When vehicle is cold (has not been run all day) the engine turns over just fine, but idle is way high, even when the curb idle adjustment screw is completely lossened, When the Engine gets warmed up, the carb stays completely closed and the engine dies and will not start back up.
The carb is a rebuilt Quadrajet.

I am guessing it could be a vacum or electrical issue, but having no diagrams, pictures, and Frankly No Friggin Clue about carbs in general; I have no idea what to do and I cannot afford to take it to a shop.

Any help is greatly appreciated.

BTW recently joined and love this site already.

[INSIDIOUS '86]

welcome to the forum!
sounds like its just hitting the fast idle and choke on the carb when its cold, thes carbs normaly idle rather high when on the fast idle in effort to warm the engine. sounds like when it warms up since you have the idle screw backed out all the way it will choke out and die, not to mention these carbs sometimes devolop a leak and will cause idle problems, so to start it pump the gas once and put your foot to half throttle and it should start make sure you put the idle screw back in its origanal position

sooner or later someone that has taken the time on this forum to understand these rat trap carbs will tell how to fix the leak and such

[ray_mcavoy]

Welcome Nathan!

When you say:

When the Engine gets warmed up, the carb stays completely closed and the engine dies and will not start back up.

Am I correct in assuming you're talking about the choke staying completely closed?

If that's the case, you'll have to see what's keeping the choke from opening as the engine warms up. I think the factory setup for 74 was a divorced choke with a thermostatic coil mounted on the intake manifold crossover and connected to the carb with a short linkage rod. Make sure it's not missing any pieces and that the linkage moves freely.

Once you get the choke working properly, the Quadrajet carbs have two idle speed screws. The curb idle speed screw you mentioned only comes into play once the choke has fully opened. There's also a fast idle speed screw (in a somewhat hidden location on the passenger side near the choke linkage) that sets the idle speed when the choke is not fully open. This is the screw you'll need to adjust to bring down that "way too high" idle when the engine is cold.

[cjlinkster]

You may want to check to make sure that there is a thermostat in the engine; otherwise the engine may not get hot enough to expand the spring in the choke housing.

Does your choke pull off pull the choke plate open (1/4") upon the engine starting or does the choke plate remaining totally closed? The front pull off should open the choke plate once the engine starts. Use a vacuum pump to test the pull offs.

There are some good videos on youtube that will help you with the quadrajet.

[NathanE]

Sorry I should have been a little clearer when I said the carb would stay closed. Yes I am refering to the choke plates, both front and rear. Today I will check the Thermostat as well as the fast idle (which I had no idea about).
As for when it is warm I had the curb idle screw at factory setting as well as various other settings in an attempt to fix it, again that is my fault for not being clearer.
I will let you all know how it goes.
Thanks again!

[ray_mcavoy]

Hi Nathan,

No problem ... I figured you meant the choke but I just wanted to be sure

And just so you know, only the front plate is the choke. The rear plates are the secondary air doors.

[rayfinseats]

Read up on Qjets on the internet. Ya the rears (secondary air doors) wont open til full throttle under a load.

http://vetteprojects.com/kstyer/quadrajet.htm

[INSIDIOUS '86]

quadra bogs, nothin but trouble lol