Gas Fumes With Full Tank

[Keyav8r]

91 Eliminator, 4.0, AX-15, 4x4, SWB - PO had the gas tank replaced due to rust. When I fill the tank there is a strong gasoline smell that gradually goes away as the tank level is burned down. Noticed it on the previous fill up but seems worse this time. Bad enough that I've parked the truck outside for the last few nights.

I'll be under the truck today, so what should I be looking for?

Vent line to the vapor canister?

Leak around filler neck?

Gas gauge is inop so I have to fill up at around 200 miles to avoid running out of gas. Could probably go a little further between fill ups as it took 13 gallons after 230 miles on the last tank.

Will be looking at the gas gauge issue today also.

Alright, MJ gurus, tell me what else I should be looking for to cure this problem.

[ComancheKid45]

Check the O Ring 2 the sending unit...theyre know to harden and start leaking fuel with a full tank. Also check the filler hose connections, 25 year old Rubber does tend to lose some of its strength. ;) 

[ParadiseMJ]

When the tank was replaced, were the rollover valves on the top of the tank also replaced? The plastic nipples on the valves do decompose over time and fuel exposure. They're also an added expense...about $50-60...when replacing a fuel tank. The evap lines that go to the charcoal canister "T" together to one line, then they attach to a metal line, that goes up the firewall, and then back in to a rubber hose. So there are 8 connections (valves[2], T [3], rubber to metal, metal to rubber, rubber to canister, that can be broken or just plain not attached.

 

If the PO didn't want to, or didn't KNOW to replace or attach the valves then fuel fumes, or fuel itself will escape/slosh out (especially with a full tank).

 

As said above the filler connection is also suspect. It consists of 2 hoses, one big one, and a 5/8" relief or return hose. Both of them are kind of a PITA to replace or re-attach as they tend to kink up if they're not attached properly. I'd also check the attachment at the fuel filter. The two little rubber hose pieces tend to get overlooked when people change the fuel filter. That generally only appears when the truck is on/running or even just with the key turned to on (the fuel system is pressurized).

[Oyaji]

:agree:

 

Both posts spot-on and a great place to start. Likely a leak atop the tank from one of the above, considering you said it is worse with a full tank and the gasoline odor weakens as the fuel level drops.

[Keyav8r]

Crawled under the truck this AM and checked fuel filter lines (OK, no leak), fuel pump/sending unit gasket (OK, no signs of leakage). Started truck (with wheel chocked and parking brake on), still no sign of leakage. Took off the plastic tank cover/skid plate thingy and found some greasy residue from rear pinion leakage (PO had the seal replaced before I bought the truck). Checked the filler and vent hoses by looking between the unibody rail and the fender and by removing the filler neck. No sign of leakage but they look like they were not replaced when the tank was

Looked closer at the tank (obviously new replacement) and saw stains running down the upper part of the front and inboard sides of the tank. Also saw some moisture between the rear tank strap and the tank. Supported the tank and removed the strap and sure enough a greasy residue but with a gasoline smell.

Lines to the rollover valves are in place and apparently intact, but look like they weren't replaced when the tank was. Didn't want to pull on them too hard and make the situation worse.

Conclusion - leakage from the top of the tank, probably from a rollover valve and/or the hose attached to it.

So I will be dropping the tank next weekend to check the valves and lines and to replace the filler and vent hoses. Probably pull the pump and sender unit while I have the tank out to see if the sender works. Don't know if I have any options if it doesn't work, but it would be nice to know if it is or isn't good.

While I had the filler neck off I was able to siphon out about six gallons. Have driven the truck about 140 miles since the fill up so I should be down to 5 or 6 gallons in the tank. I'll drive it a little more during the week to get the fuel level as far as I can to make pulling the tank easier and safer.

Thanks for the info. That's what I really like about the forum. There's usually someone who's been there, down that and is willing to provide the "how to" and the "watch out for" info.

[Keyav8r]

Don't have access to my manuals now. Found the following parts on Team Cherokee.

 

Fuel Filler and Vent Hose Kit PN 52000623 - listed for Cherokees, not sure if they will work on a 91 MJ. Anybody have the MJ PN or know if these will fit?

 

Fuel Pump and Sender O-ring PN 53000575 - listed for MJ and XJ

 

Vent (Rollover) Valve PN J5360058 - listed for MJ and XJ (2 required)

 

Grommet for above valve PN 52018823 - listed for MJ and XJ (2 required)

 

Push Nut Set (4) PN 3420214 -listed for various applications on XJ - possibly correct for the push nut on the fuel pump/sender plate?

 

The fuel pump and return hose, the vent hoses and the vacuum tee should be available from NAPA, etc.