Fuel Tank vent lines and all that goes with it?

SurfnCJ8

Legacy Registered User
SOA Member
City
Wilmington
State
NC
#1
1984 w/4.0 ( I think from a 98 Grand Cherokee but that is a question/topic for another thread) & 20 gal tank. All done before I got the jeep so quality of installation and correctness is an unknown.

With this extra stay at home time I have lately I started getting the jeep ready for the warm weather. Sunday I went and filled it up and it started leaking fuel. Turns out it was coming from a smaller hose on drivers side that I am guessing is a vent. Looks like there are a handful of hoses that size wedged up along the frame rail, with at least this 1 that is leaking not attached to anything. Before I started just aking things apart I did a some searches trying to find what is supposed to be there, but didn't find a good diagram yet. What I am trying to find out is:

1. What is actually supposed to connected in the fuel venting system and how is all attached/put together

2. What is the minimum necessary for it to function safely and properly ( if things from question 1 aren't all necessary)

Any help /info is appreciated. Hope everyone is doing well and staying safe!

thanks, Tom
 

walkerhoundvm

Just trying to stay upright
LIFETIME
CJ-8.com Member
City
Cave Creek
State
AZ
#2
That 20g tank (if it's OEM) should have two check valves on top plugged right into the tank. They connect to one another with a Y piece and some rubber line; the third arm of the Y goes to a line all the way to the charcoal canister. From there it's just a matter of vapor scavenging to the throttle body.

It's pretty simple on the 20g, a little more complicated with the 15g.
 

SurfnCJ8

Legacy Registered User
SOA Member
City
Wilmington
State
NC
#3
Thanks. I think charcoal canister is missing as well. I am off tomorrow so I need to crawl around the jeep some and see exactly what lines are there and where they are running.
 

Spieg

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Aurora
State
CO
#4
Being that it's an unknown, I'd probably drop the tank and see what the PO did. Assuming it has EFI with that 98 engine, you want to look things over pretty carfully. EFI requires more psi than the original carburetor and you want to be sure where the pump is (in tank or external pump, or both) and that the correct fuel line is used in the correct places.
 

SurfnCJ8

Legacy Registered User
SOA Member
City
Wilmington
State
NC
#5
It is EFI and the pump along with a filter is mounted along the passenger side frame rail. I will look at all that as well while I am at it. Thanks for the suggestion. I think that the PO I purchased from had the motor swap done at a local( to him) jeep shop so hopefully they did a decent job. I have had the jeep a few years now but all I use it for is running around town and going to the beach. It runs OK but is overdue for a good looking over.
 

SurfnCJ8

Legacy Registered User
SOA Member
City
Wilmington
State
NC
#6
Was doing a google search and found this pic from an old thread on here. Very Helpful.



1493AE17-DAE5-4F02-89F0-7E3B70DBD123.jpeg
 

walkerhoundvm

Just trying to stay upright
LIFETIME
CJ-8.com Member
City
Cave Creek
State
AZ
#7
That's for the 15g tank only. If you had a 15-20g swap, some of the hardware may still be in place (and likely bypassed), but if the 20g was in there from the start, almost none of it will look the same.
 

SurfnCJ8

Legacy Registered User
SOA Member
City
Wilmington
State
NC
#8
Most all of my hardware is missing. Did find the charcoal canister in a box with a bunch of old jeep parts so I need to look it over. Found a replacement check valve online with the place for the 2 vent lines and the line to the canister. Traced all my vent lines and those are all there so that is good. Hunting now for threads / info on how and where folks who have done the 4.0 swap ran the lines for vapor scavenging from the canister.
 

walkerhoundvm

Just trying to stay upright
LIFETIME
CJ-8.com Member
City
Cave Creek
State
AZ
#9
TRex autoparts or something like that is where I got my check valves. You will need two. Careful - they're kinda poorly made, the aluminum cup filters aren't pressed very well and can fall off. My vapor line is run up the inside driver side frame rail, in parallel with the brake lines. Canister sits just under the coolant reservoir behind the front P wheel well.

TRex also sells the fuel sending unit with MTS listed as the manufacturer, but they're just rebranded Crown or Omix parts. They can also have quality issues, so you'll need to test the ohm readings out before installing one.
 

Spieg

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Aurora
State
CO
#11
Jeep YJ 20 gal tank used the same check valves as the CJ... Last time I checked you could still get them from the Jeep dealer.
 

SurfnCJ8

Legacy Registered User
SOA Member
City
Wilmington
State
NC
#12
Bought and installed this the other day. Supposed to take the place of both stock pieces. Should be OK. Now to see about the charcoal canister. Resized_20200408_191548.jpeg
 

Spieg

Scrambler Junkie
LIFETIME
CJ-8.com Member
City
Aurora
State
CO
#13
Interesting... I can't really picture how that would be installed. Can you please post up some photos of the installed piece? Would also love to see the gas tank and skid plate.
 

SurfnCJ8

Legacy Registered User
SOA Member
City
Wilmington
State
NC
#14
I will post some pics the next time I get a chance to work on it. Hopefully tomorrow but we are doing some house remodeling so my honey do list is pretty long. Basically my two gas tank vent lines connect to the double connector and then the single runs to the charcoal canister that I have not put back in yet. Of course after I bought that and installed it I was going through some boxes of old Jeep parts that I have and I found the original setup. 20200416_161346.jpg
 

walkerhoundvm

Just trying to stay upright
LIFETIME
CJ-8.com Member
City
Cave Creek
State
AZ
#15
I will post some pics the next time I get a chance to work on it. Hopefully tomorrow but we are doing some house remodeling so my honey do list is pretty long. Basically my two gas tank vent lines connect to the double connector and then the single runs to the charcoal canister that I have not put back in yet. Of course after I bought that and installed it I was going through some boxes of old Jeep parts that I have and I found the original setup. View attachment 82430
The larger piece tends to be in good, working condition. The smaller piece is usually rotted, though there is a direct replacement from DMC (yes, that DeLorean motor company) https://store.delorean.com/p-6703-rollover-check-valve.aspx
 
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