Need advice on how to tackle an issue on my '86 305

[AMRAAM_Enjoyer]

One thing you can do is unbolt the charcoal canister, pull it out and carefully shake it. If you can hear fuel sloshing around, it's junk. I've always done away with the charcoal canisters and just vented to atmosphere but I remember reading on here that simply letting them dry out doesn't work either, apparently once the charcoal is soaked with fuel, it's essentially ruined. There's some universal charcoal canister setups but I don't think anyone repops an identical one at this point

I'll check that out and see when I get home from work. When routing to vent to atmosphere, is there any particular ideal path to follow? Or just any method to get it away from the truck?

 

[Ricko1966]

I'll check that out and see when I get home from work. When routing to vent to atmosphere, is there any particular ideal path to follow? Or just any method to get it away from the truck?

Just pull the hose at the cannister and stick a clear plastic fuel filter in it. The filter will let it breath but keep dirt and bugs out.

 

[SquareRoot]

At the moment, I drilled a 1/4 hole in both caps and that fixed the drivability issue. However, I can smell raw gas fumes around the vehicle and with the drivers window down. So I don't plan to leave it like that. I ordered and received a new 3 port cannister ($80) from Summit and a new check valve. Hopefully, check the lines and get it working right this weekend if I don't melt first. It's supposed to be 116 today

 

[Grit dog]

Thats my conclusion as well! Thank you both very much. I have new lines and a new gas cap on order so I am going to give that a shot. In the meantime I will give it a go with drilling a hole in the gas cap and see what that yields.

I admire the enthusiasm but fwiw, I’d have diagnosed the problem before buying new parts.
You haven’t said whether your 86 is plumbed up all as original or if it has any combination of fuel pumps, lines vents etc.

 

[TotalyHucked]

I'll check that out and see when I get home from work. When routing to vent to atmosphere, is there any particular ideal path to follow? Or just any method to get it away from the truck?

I always just go out of the tank and bring it back along the frame rail on that side. On my '85, there's clips for the rear harness that I just pressed the line into and it ends about 6" in front of the rear bumper, nothing fancy. I might've used a zip tie in a spot or two to make sure it stayed, can't remember now. Some people put a rollover valve/one way valve to help with smell but mine is just open.

 

[AMRAAM_Enjoyer]

One thing you can do is unbolt the charcoal canister, pull it out and carefully shake it. If you can hear fuel sloshing around, it's junk. I've always done away with the charcoal canisters and just vented to atmosphere but I remember reading on here that simply letting them dry out doesn't work either, apparently once the charcoal is soaked with fuel, it's essentially ruined. There's some universal charcoal canister setups but I don't think anyone repops an identical one at this point

I'll give that a shot as well. Thank you!

 

[AMRAAM_Enjoyer]

I admire the enthusiasm but fwiw, I’d have diagnosed the problem before buying new parts.
You haven’t said whether your 86 is plumbed up all as original or if it has any combination of fuel pumps, lines vents etc.

Yeah, probably a bit foolhardy on my part. But I figured that new fuel lines on a truck that wasnt driven all too much couldnt hurt. And yes, I do apologize, it is plumbed up as original. Charcoal canister, main, return, and vapor line, mechanical fuel pump, etc. Cross referenced with the fuel system diagram in the Chilton manual and it is a 1 for 1 to what is currently on the truck.

 

[AMRAAM_Enjoyer]

I always just go out of the tank and bring it back along the frame rail on that side. On my '85, there's clips for the rear harness that I just pressed the line into and it ends about 6" in front of the rear bumper, nothing fancy. I might've used a zip tie in a spot or two to make sure it stayed, can't remember now. Some people put a rollover valve/one way valve to help with smell but mine is just open.

Okay cool. Coming from fuel injection, this is all a bit new to me, especially considering I have never really had to mess with fuel system stuff before so this is all wonderfully useful knowledge to have for the future. My plan is to use what I learn on this truck to be a backbone for future projects down the line, so you have my thanks!

 

[TotalyHucked]

Okay cool. Coming from fuel injection, this is all a bit new to me, especially considering I have never really had to mess with fuel system stuff before so this is all wonderfully useful knowledge to have for the future. My plan is to use what I learn on this truck to be a backbone for future projects down the line, so you have my thanks!

Hey, we're glad to help! Funny enough, my truck is fuel injected too lol (LS swapped), venting like that is an option whether carb or FI. Especially as old as these are and it's hard to find replacement parts to keep it a closed system with the charcoal canister, it's pretty common to just vent them like that.

I have seen a couple guys on here come up with a homemade charcoal canister setup to help with fumes, it was just a small glass fuel filter that was gutted and filled with charcoal pieces with hose run to and after it. Would also be a good option in the off-chance your truck does fume more than mine. I think they mounted it on the core support, but something like that could go along the rail as well or pretty much anywhere since it's small

 

[Grit dog]

Yeah, probably a bit foolhardy on my part. But I figured that new fuel lines on a truck that wasnt driven all too much couldnt hurt. And yes, I do apologize, it is plumbed up as original. Charcoal canister, main, return, and vapor line, mechanical fuel pump, etc. Cross referenced with the fuel system diagram in the Chilton manual and it is a 1 for 1 to what is currently on the truck.

No apologies needed. I have parts never needed and not returned sitting around due to doing the same thing sometimes. Only reason I mentioned it.
Good news it’s not cobbled together, that helps. I was kinda assuming it was because in my limited experience it’s more common to pull a vacuum in the tank with a plugged vent. Maybe someone like @Ricko1966 has an explanation for the positive pressure?

 

[Ricko1966]

I admire the enthusiasm but fwiw, I’d have diagnosed the problem before buying new parts.
You haven’t said whether your 86 is plumbed up all as original or if it has any combination of fuel pumps, lines vents etc.

That was the point of the no cap test. Oh well.

 

[AMRAAM_Enjoyer]

Hey, we're glad to help! Funny enough, my truck is fuel injected too lol (LS swapped), venting like that is an option whether carb or FI. Especially as old as these are and it's hard to find replacement parts to keep it a closed system with the charcoal canister, it's pretty common to just vent them like that.

I have seen a couple guys on here come up with a homemade charcoal canister setup to help with fumes, it was just a small glass fuel filter that was gutted and filled with charcoal pieces with hose run to and after it. Would also be a good option in the off-chance your truck does fume more than mine. I think they mounted it on the core support, but something like that could go along the rail as well or pretty much anywhere since it's small

No apologies needed. I have parts never needed and not returned sitting around due to doing the same thing sometimes. Only reason I mentioned it.
Good news it’s not cobbled together, that helps. I was kinda assuming it was because in my limited experience it’s more common to pull a vacuum in the tank with a plugged vent. Maybe someone like @Ricko1966 has an explanation for the positive pressure?

That was the point of the no cap test. Oh well.

You guys are legit heroes. Went home on for lunch, popped the gas cap off drove to Mcdonalds and back. Let the truck sit with the cap off while I ate, went back outside after about 15 minutes and the first start didnt catch but the second one did and she idled rough for about 5 seconds and then she was solid. I am now positive its a venting issue. Thank all of you so much, I wouldnt have thought of this probably for another week or so. Hell, I was pricing out 4 barrels and intake manifold cause I thought the little 2 barrel might have just taken a **** and figured "why not upgrade?" lol. Regardless, thank you!

 

[AMRAAM_Enjoyer]

That was the point of the no cap test. Oh well.

Wasnt really clear as to when I ordered those. My mistake, I placed that order a few days before I started this thread. So they were already on the way.

 

[Turbo4whl]

Interesting, so based on this experience, it may very well be possible that the charcoal canister is clogged up, or the vapor line is, maybe even both. It would make a lot of sense. Thank you for the input!

Yes, the charcoal is for fuel vapor only. If raw fuel gets sucked in somehow, it melts the charcoal into a lump (clog).

 

[olnick]

My tank does the exact same thing! Only difference is is does this on the tank that I am NOT running off of. Each tanks vent is sealed off when NOT in use and is vented when in use!
Are you running dual tanks????