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I dropped the tank for a cleaning, and a new fuel sending unit, while I'm at it I'm going to address the fuel lines, and the fuel tank vent, the vent hose was plumbed to my transfer case, my j10 has none of the emission stuff on it, what did you guys do for the vent hose? I'm thinking run it high and dry like for a differential vent? I don't want to just plug it off...

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Fuel tank vent should run up to the charcoal canister, to run fumes through to the carb.
Gotta love POs creative thinking....EH?

Yeah, this thing has sat for about 16 years now, 15 years ago the p.o. took the motor out and did a rebuild on it and deleted all that stuff....I mean I like the simplicity but some things are just better to stay put...lol

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In that case yes, just run it up the front of the bed, and put a little filter in the tip of the line. Maybe the PO thought gas fumes in the transfer case would give it more power to the tires?

Agreeing with above, yes you can run the vent quite high behind the filler neck cover. You need the vent to be open to the atmosphere, and allow air into the tank as the fuel is removed. The original filler cap will have no vent. A cheap fuel filter works good as a vent. This is what I did with my transfer case vent on my '82 J20.

Likely the PO did not understand the plumbing and connected whatever was disconnected.

I just did this my self, my grommets for the two vents (wagoneer) were shot. Might be a good time to replace both.

Might be difficult to replace both for the OP. There's only one vent on a J-truck tank.

the amount of fuel evaporation loss thru the vent line is so nominal , and the vent canister was a government EPA sham , think about it, where did ALL THOSE HIGHLY IMPORTANT fuel vapor recovery filler necks go at the gas stations GONE there is more fuel vapor loss at fill up than during a tank being driven dry, run a vent line to a high point and attach a fuel filter to prevent contamination as there is a very slight vacuum as fuel gets consumed from the tank , if there were no venting you would have on going on/off fuel starvation issues due to a sealed tank (no venting)

So far dealing with bj's hasn't been a very good experience....do any of you know where to find a fuel sending unit for an 84 j10? I can't find any online anywhere, and some folks seems to be trying to pass off wagoneer fuel sensors for j10's...

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The '80 listing shows a Jeep PN 5359793. The '81J book lists a J5363977 as the proper replacement for '84-86. Could not find a listing for the '81-83 part... likely either of the above would work.

Looking online, I found no current source for the 3977. The 9793 leads to several places that list the MTS JPSU-3 as the proper replacement. The few of those I looked at all said out of stock.

I would call MTS tomorrow and ask about availability. They may be able to point you to one of their retailers. Likely BJs is selling the MTS part, if they have stock.

Bj's and mys both are out of stock I guess, but I'm gonna make some calls tomorrow....

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My 76 J10 has no vent on its original tank.. no charcoal. No cats. I think 76 was the last year for this.

Only (vent) mine has is the large breather that goes up to the filler neck