Need blazer tank swap help!

[big steve-o]

So, I put a 25 gallon tank from a 1980 k5 blazer in my 85 gmc 1500. The filler neck is giving me fits. One, the tank does not have a vent line like the old one did, that came out next to the filler hole via a hose that runs alongside the filler. So the gas bubbles back when I pour it in. Also, the center 3/8 line on the sending unit from my old tank was capped off. What was that, return line? If so, can I run that to a vent? Next, I can't seem to get the line to stay running downhill from the filler to the tank, it goes over the frame rail, and to my fuel door behind the rear wheel. Truck Used to have a tank back there, and the bed support channel is notched for the neck, but even that sits too low, causing fuel to puddle in the neck and not drain to the tank. I am getting very frustrated, as this is my daily driver, and I can't seem to get the tank to work right! Also, if you're about to link capt kaos' blazer tank swap, none of this is in it.

[clapage6]

i can only chime in on the 3/8 line on your sender. cause my 6.2l crew had those 3 tube senders. 1 5/8 feed, 1 3/8 return, and one 3/8 line went to a spout that was used to drain water from the tanks if needed. you can cap it off as usual. it wont work as a vent because that tube runs all the way to the bottom of the tank as i believe this is where the water would be if you had a lot of water in the tank somehow. do cap it tight though cause as the gas sloshes around and gets hot it can create some pressure if the cap isnt vented and will start to leak through that 3rd line.

And just an observation that your pump cutting off issue is most likely related to that "hump" in the filler neck. Fix that somehow and your filling problem should go away also

[big steve-o]

It seems like the center 3/8 line ends right at the top of the sending unit. I could be wrong, but unless some hidden trickery is afoot, the only line that extends to the bottom of the fuel tank is the main supply line with the sock on it. I suppose it has to have a vent for both allowing air to escape during fillup, and allowing air in as fuel is taken out. I must be missing something, but what?

[clapage6]

ahhh i looked at some pics online and i see the difference now.... the diesel ones have one of the two 3/8"ers going all the way down but the senders for the gas engines do not, I have no idea what that 3rd is there for then :-p good luck buddy..

[motornut]

my 79 Jimmy
3/8 main feed to the bottom
1/4 return
5/16 vent
1/2 inch fill vent

[jitteryguy]

I had the same issue's with the 25 gal. Burb I put in my CCSB, the only thing I could come up without cut'n the bed any ware was to raise the bed floor a few inch's so the neck can have a little angle, I pull'd mine back out and will use it my Dually that has a raised bed floor.

[big steve-o]

So, if the main line and the small line on my sending unit are both hooked up, is the middle line a vent that was plugged because the old tank was otherwise vented? Can I just unplug and run the hose somewhere and use it for a vent?**edit** just thought about what I was asking and it became fairly obvious that I either need to drill some other vent line into the tank, or get the sending unit from the blazer with the full vent. Gotta see if I can get the s.u.

[jitteryguy]

I vent'd mine from the send'n unit, it didn't help with fuel'n though.

[big steve-o]

Finally bit the bullet and bought the Blazer sending unit. Hooked up all the lines and vents, but still had to go through the bed floor. Put my filler behind the driver side wheel hump, just barely noticable. Didn't want to go through the bed, but it fills without incident. I can put the pump on full blast and lock it, and it works just fine. If I had any advise for others looking to do this swap, I'd say buy the right sh!t up front and save the headaches, but otherwise go for it. Now I just need to figure out some nice looking cap ideas.