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Old 11-23-2019, 11:23 PM   #1
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Location: Central OR
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Charcoal Canister Delete Questions

My 81 K30 454 had no canister in it when I bought it. Holley, Edelbrock, Headers, and an in and out mechanical pump all ready on it. I did not pay any attention to the smog delete until today while bleeding the Hydroboost after installing a new steering gear box.

I have gasoline draining out the drivers side front axle tube at the yoke. So I followed the front diff breather hose up to the front cross member and over to the drivers side, to what I believe is the hard line from the tank to the former charcoal canister.

It got dark and cold so I came in to do some research.There are 2 hard lines next to the steering box that have a rubber hose connecting them in a loop. I need to figure out what they are for. I have always had problems with the pass side tank overflowing even though I never use it. My hose routing must be really messed up.

The questions are... What do you all do with the breather line from the tank to the former canister? Cap it or let it vent somewhere? Why in the world would my diff be filling from a wrongly connected vent line with fuel flowing in it. One would think the vent line would be connected high up in the system to not be in contact with liquid. As I said my routing must be really messed up.

Thanks for any help and I hope you got a good laugh out of this.
1955 GMC 250 8 Flatbed
1971 C30 157" 350 4spd PS PB White With Blue Int 10' Flatbed
81 GMC K30 CnC 9' Flatbed 454 T400
71 LT1 Convertible, 72 Coupe
69 CJ5 V6, 75 CJ6 V8
67 M715, 72 M35A2 Bobbed, 95 XLC2
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Old 11-24-2019, 02:02 AM   #2
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Location: Sunray,TX
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Re: Charcoal Canister Delete Questions

If I remember correctly, the front diff vent has a clamp and one of those breather cap things on the end. The clamp bolts to that same crossmember that the tank vent comes across I think.

On one of my rock crawler jeeps, I run the tank vent up and over the brake booster, then have it tied to the side of the frame to limit any vapors or liquid from getting where it shouldn't.

If I were in your shoes, I would hunt down all the charcoal stuff and hook it back up, but that's just me. I don't like my truck to smell like gas in the garage. If you wanted to do it like I did on my jeep, that would work great too, just pay attention to where the vapors and liquid could contact exhaust, etc.
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Old 11-24-2019, 08:49 PM   #3
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Re: Charcoal Canister Delete Questions

If one tank is overflowing the return lines off the tank switch valve are hooked up backwards... the fuel is being returned to the tank that's not in use. Fix this ASAP before you have a fire.

The fuel tank vent lines should route to the charcoal canister. Really no reason to delete the charcoal can. It keeps the barn from smelling like gasoline and it doesn't cost any HP to keep it in working order.

Someone tied the tank vents to the front axle vent... Your axle vents should terminate in a vent cap. Rear is a hose with a vent hooked on the bottom of the bed. I've never seen a front vent that's hooked up in the original location. I run mine up to the frame and terminate with a vent fitting near the top of the frame.

I'd check to make sure whomever borked the hose routing didn't hook the tank vents to the transmission and transfer case to fill them with gasoline.
1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8

RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
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