vacuum line, please help

[gikken20]

Where does the vacuum line come from that goes here? the truck starts and idles and I can rev it up but when I put it in gear and give it any gas it dies, im guessing its choking itself out??? its a 68 GMC with a 350 and a quadrajet, Thanks,
since i just got my truck back after it sitting at my parents for 6 years ill post a bunch of pics once i get it cleaned up

[geezer#99]

It plugs into the manifold vacuum port on the back of your carb. It's your choke pull-off canister. If it's working right when you start up the vacuum pulls the choke blade open about a 1/4 inch.

[a2tripp]

you need to find the hose that plugged into it

[lil hoodlum]

Originally Posted by geezer#99

It plugs into the manifold vacuum port on the back of your carb. It's your choke pull-off canister. If it's working right when you start up the vacuum pulls the choke blade open about a 1/4 inch.

completely correct!!!! You rock!

[100%Chevy]

Nothing goes where your arrow is pointing.There's a hole for an allen wrench to adjust it with.
The hose is on the side of the diaphram,behind the carb,and it does go to the base of the carb.
I have the same or similar carb on my 68,c-10.
Mike.

[gikken20]

Originally Posted by 100%Chevy

Nothing goes where your arrow is pointing.There's a hole for an allen wrench to adjust it with.
The hose is on the side of the diaphram,behind the carb,and it does go to the base of the carb.
I have the same or similar carb on my 68,c-10.
Mike.

Awesome, it's been driving me crazy trying to find what goes there, my father was in the process of selling it until I got orders to fort Lewis and I could get it, a young kid had made a payment on it but couldn't come up the rest of the cash and he had messed around with it some so I didn't know if he had disconnected anything, when I fire it up it idles fine and will rev up with a little lag, when I put it in gear and give it gas it dies, what could it be? It took me awhile but I was able to drive it on and off a flatbed but it's been sitting for 6 years almost only being started occasionally, it's a quadrajet and I think the secondary's are not opening
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[geezer#99]

Check ball could be stuck in the accelerator pump discharge line. Stroke the throttle with the engine shut off and you should see two strong streams of fuel blasting into the carb below the choke plate. No fuel comes out then your check ball is stuck. Carb has to come apart to fix it.
Another possibility is secondary air valve set too loose. Tap it with your finger and it should snap shut. A quick opening of the air valve causes a big bog. Air valve is the big door at the rear of the carb.
Here's a link for quad info.
http://www.digitalcorvettes.com/foru...ad.php?t=88376

[lil hoodlum]

If the arrow is pointing to the rear vacuum break assembly (Choke pull off) then yes, there is supposed to be a vacuum hose attatched to it that goes to the base of the carburetor.

http://www.tocmp.com/manuals/Carbs/R...QJet/index.htm



Keith

[geezer#99]

Awesome diagram.
The checkball I speak of is #39 which is located under screw #40.

[gikken20]

So after looking into it more 100%Chevy is right about the adjuster for the diaphram, I pumped the gas while looking into it and only the pass. side is getting fuel, what's the best way to clean the injectors or do I have to rebuild it, I'd rather not rebuild it right now till I have some more cash cause last time I took a Q-jet apart I had to take it to my boss in a box to put back together so I'll have to have it rebuilt
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[gikken20]

so the fuel is coming out where the yellow arrow is, not to ask a stupid question but its supposed to come out at the red arrows right? is it a bypass or is it just jacked up, also the 2 screws are to adjust the fuel flow right? the right one was all the way turned in and when i backed it out no fuel came out, what should they roughly be at?

[wildearp]

Get a hand vacuum pump and check that vacuum pot. I replaced several of them for cracked diaphrams. Good chance it doesn't work even if hooked up right. I could only get about 2 years out of them.

[gikken20]

Originally Posted by wildearp

Get a hand vacuum pump and check that vacuum pot. I replaced several of them for cracked diaphrams. Good chance it doesn't work even if hooked up right. I could only get about 2 years out of them.

Could you elaborate more on how to do this please, I haven't messed with carbs really so where would I hook it up and do I need to block anything off? Thanks
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[geezer#99]

Which 2 screws are you talking about?

[gikken20]

The screws just inside of the red arrows
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[geezer#99]

Originally Posted by gikken20

The screws just inside of the red arrows
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Those 2 screws should be tight. They hold the top of the carb onto the main body of the carb.
The fuel should come out where the yellow arrow is. The red arrows point at the venturis where the fuel from your jets is discharged to mix with the air coming into the carb.
No fuel out the accelerator pump discharge on the right side might mean a plugged line or insufficient volume. Push down the plunger on the accelerator pump so it's flush with the top of the carb. Do it quickly and see how much discharge you have then. The pump lever is adjustable if needed. There should be 3 holes in the end of the arm.

The plunger is # 54 on the diagram. Pump arm is #3.
To check the vacuum pot hook up a longer hose to the pot and suck on it hard to see if it moves. Put your tongue over the end of the hose and when you release the suction you should hear the pot snap shut. Don't need no fancy hand vacuum pump if you got good lungs. LOL!!!

[gikken20]

Thanks geezer#99, is there a way to clean the line without taking the carb apart? I have two holes on the plunger so I'll reinstall the carb in the morning and see about it.
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[geezer#99]

Just sharply push down the plunger first to check flow. You don't need to stroke the throttle to do that. Use your finger on the tip of the plunger. Or use a flat screwdriver. You don't even need to have the carb installed as long as there's fuel in the bowl. You can trickle a bit of fuel into the bowl thru the round vent hole at the top of the carb. THe hole right in the middle of your pic.

[gikken20]

I know this will probably be hard to explain but am I looking for like a water gun stream or like it's pouring out, also what about if the lines plugged, thanks again for taking the time to help me
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[geezer#99]

Similiar to a water gun stream. A good squirt is more like it. If one side gives a strong squirt then do it a few times. Might unplug the other side. Manually pushing the plunger gives you maximum flow. Stroking the throttle only gives you a partial shot depending on what hole the lever rod is in.
If you do this with the carb off the motor you don't need to worry about flooding the motor.
I had a carb once with one discharge port that was strong and the other side weak. I adjusted the lever for max flow by putting the rod in nearest hole to the pivot. Worked good long enough till I had a chance to tear the carb apart and flush it out.
If you need help to adjust the rod hole let us know. There's a couple tricks to it. Easy to do but tricky for the rookie. LOL!!