84 C10 charcoal canister line question

[Taylorb27]

Replaced the current qjet with a good older rebuilt one I had due to not having to hack up the baseplate to get to the idle mixture screws. Older one does not have a front port coming off the fuel bowl. I'm guessing the older pickups had that line running to the air cleaner? If they even had charcoal canisters I guess. Carb is from a 72 Chevy Blazer. Thanks!

 

[1987 GMC Jimmy]

Does your emissions call for both a ported and manifold source? I believe it does on the spaghetti years. If there’s only one source of vacuum for the canister, it should be ported so it doesn’t constantly purge. You can just test the carb ports for ported with a vacuum gauge. Whichever one is dead at idle is the ported.

 

[Taylorb27]

Does your emissions call for both a ported and manifold source? I believe it does on the spaghetti years. If there’s only one source of vacuum for the canister, it should be ported so it doesn’t constantly purge. You can just test the carb ports for ported with a vacuum gauge. Whichever one is dead at idle is the ported.

Sorry I should have added more. I do have the small ported line hooked up to ported, also have the bigger hose Tee'd to the pcv valve. But my original carb had a larger port on the front, top portion of the carb that came out at a 45° I assume went to the fuel bowl. This carb off the 72 350 does not have that. I'm guessing that line was for bowl fumes, just don't know whether to hook it to a port on the air cleaner (beings there's one that goes off in that direction right now) or cap it.

 

[C10MixMaster]

Sorry I should have added more. I do have the small ported line hooked up to ported, also have the bigger hose Tee'd to the pcv valve. But my original carb had a larger port on the front, top portion of the carb that came out at a 45° I assume went to the fuel bowl. This carb off the 72 350 does not have that. I'm guessing that line was for bowl fumes, just don't know whether to hook it to a port on the air cleaner (beings there's one that goes off in that direction right now) or cap it.

yes that's from the float bowl. No the earlier models had a simpler charcoal canister that only did the gas tank/s. Your best bet is to probably cap that line at the canister or use the older style canister.

 

[Taylorb27]

yes that's from the float bowl. No the earlier models had a simpler charcoal canister that only did the gas tank/s. Your best bet is to probably cap that line at the canister or use the older style canister.

I wonder if having this hose open is causing a vacuum leak? When I bought this pickup it would not idle. Would hold any rpm above 1000 fine but nothing less. The spaghetti mess of vacuum lines were rotted so I removed everything that didn't have to do with essential engine function. That line was cut for some reason. The only reason it runs fine now is because I put the older carb on and have the idle screws turned out 3 turns.

 

[gotyourgoat]

I wonder if having this hose open is causing a vacuum leak? When I bought this pickup it would not idle. Would hold any rpm above 1000 fine but nothing less. The spaghetti mess of vacuum lines were rotted so I removed everything that didn't have to do with essential engine function. That line was cut for some reason. The only reason it runs fine now is because I put the older carb on and have the idle screws turned out 3 turns.

You might be on to something.

Fwiw most of canisters for the older squares had less hoses routed to the canister than the later squares.

 

[C10MixMaster]

I wonder if having this hose open is causing a vacuum leak? When I bought this pickup it would not idle. Would hold any rpm above 1000 fine but nothing less. The spaghetti mess of vacuum lines were rotted so I removed everything that didn't have to do with essential engine function. That line was cut for some reason. The only reason it runs fine now is because I put the older carb on and have the idle screws turned out 3 turns.

ok the bowl vent line should not cause a vacuum leak. when the engine is running that line is not in use , it only vents when the engine is off.

 

[gotyourgoat]

ok the bowl vent line should not cause a vacuum leak. when the engine is running that line is not in use , it only vents when the engine is off.

If you have diagrams for the vaccum ports on a quadrajet I'm all eyeballs.

 

[Turbo4whl]

If you have diagrams for the vaccum ports on a quadrajet I'm all eyeballs.

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[C10MixMaster]

If you have diagrams for the vaccum ports on a quadrajet I'm all eyeballs.

You must be registered for see images attach

 

[Rusty Nail]

Everybody gotz eyeballz theze dayz but junior aint got no pikz! grr

 

[75gmck25]

My original ‘75 Quadrajet has the canister purge nipple on the lower driver’s side, but I’m now using an ‘85 Quadrajet that does not have the nipple.

I first T’d the canister purge line into the PCV line, and it seemed to work fine. But it also seemed to be running lean at cruise, so I ran the canister purge up to a nipple I put on the air cleaner, so it would pull vapor out. Carb still runs lean at cruise, so I think I’ll move it back to the PCV line.

My ‘75 canister is a simple vacuum line setup, where the port on the carb controls it and there is no purge valve in the canister. Newer vehicles apparently have purge valves that provide more control over when the purge line is connected to vacuum.

Bruce

 

[Taylorb27]

Seeing as I have some qjet knowledge in this thread I may as well ask my other question. Am I able to easily adapt the electric choke from my original carb to this carb? Beings the choke pull off is on the primary side rather than the secondary side like the original 84 carb is set up?

I really appreciate the responses! Btw I just ran the line in question to a nipple on the air cleaner that exited pointing towards the canister

 

[gotyourgoat]

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Might give Ol brown a pop quiz on this later. Not sure she's gonna pass though.

 

[75gmck25]

I am using a Quadrajet from an ‘85 or ‘86 truck, and I bought an electric choke conversion kit from Cliffs High Performance. I believe the kit is universal and will work with several models, so maybe you can move yours over from the old carburetor. The kit is only the choke cap and electrical connection, so all the linkage remains the same.

I’m not sure I can find the directions right now, but I recall having to plug/cap the port on the lower part of the choke housing when I converted to electric. The old hot air choke pulls air through the housing (to heat the element?) and you cannot leave the port open. You also remove all the hot air choke tubes and cap the hot air choke well with a small block-off plate on the manifold. It’s a quick and simple conversion.

Bruce