gas smell

Hi guys, I need some help. My 1996 XJ has had a bad gas smell that turned out to be a leaky tank. I just replaced the tank this past weekend with a new one and drove the jeep over 200 miles in the last 2 days without a problem, but now i am getting a strong raw gas odor coming from the passenger side rear wheel well. I got under the jeep while it was running and checked and there is no leak from the seal on the fuel pump, the gas line from the fuel pump to the fuel filter and no smell or visible leak from the filler neck (i didnt remove the guard though) but there is no smell at all from the drivers side. the smell is only from the passenger side! the only thing that comes to mind is the 2 vent tubes on top of the fuel tank.

any ideas?? i know i will probably have to take the tank back down this weekend but was hoping someone here might have some ideas.

thanks in advance!

might be the vent tubes. check all hoses that lead to and from the tank..... i'll gamble on this one and say that its going to be the seal in the pump.... i had the same thing happening to me 2 months ago when i failed emissions. turns out that it was the seal being dry and cracked.... :wave:

I had the same issue (really rusty tank) and couldn't find a good one at the junkyard, so I ended up swapping in a 97+ tank+pump. My fuel gauge no longer works (working on fixing that, but it'll require some fun electrical magic) and I now have the 97+ check valve and two fuel filters in my line (one on top of the pump, one in the line) but it seems to run just fine. Plus, it'll never rust out again because the new tank is HDPE.

kastein said:

I had the same issue (really rusty tank) and couldn't find a good one at the junkyard, so I ended up swapping in a 97+ tank+pump. My fuel gauge no longer works (working on fixing that, but it'll require some fun electrical magic) and I now have the 97+ check valve and two fuel filters in my line (one on top of the pump, one in the line) but it seems to run just fine. Plus, it'll never rust out again because the new tank is HDPE.

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On the gas gauge--at some point the rocket scientists of Chryco decided it would make sense to reverse the ohm readings of the fuel gauge--old was Empty = 1 ohm, Half = 44 ohms, Full = 88 ohms suddenly became reversed (I don't have the exact ohm numbers on hand).

Good luck with figuring things out on that--to my knowledge no one else has.

joe_peters said:

On the gas gauge--at some point the rocket scientists of Chryco decided it would make sense to reverse the ohm readings of the fuel gauge--old was Empty = 1 ohm, Half = 44 ohms, Full = 88 ohms suddenly became reversed (I don't have the exact ohm numbers on hand).

Good luck with figuring things out on that--to my knowledge no one else has.

Click to expand...

I'm actually looking into building a small module / extension cable combination that uses an ADC, a microcontroller, and a digital potentiometer to allow the installation of a 97+ tank/pump assembly in a pre-97 XJ. I haven't done much except scratch my head while looking at the two pump assemblies side by side though, I need to get around to looking at the wiring diagrams in the relevant FSMs and figuring out which color codes go where. The variable resistor assembly on the pre-97 assembly appears to be two laser trimmed variables connected in some strange way, ground referenced, with multiple leads to the gauge/ECU, while the 97+ is a simple two-lead variable resistor interface.

The 95 FSM I have shows a much simpler circuit, more in line with the 97+ design (and like you say, resistance/level coefficient inverted) so I am going to have to just screw around with a DMM I guess.

EDIT: They also changed the pins around a little on the connector to the fuel pump (C307 on a '95 it looks like). I think their rationale for swapping from empty=1ohm to empty=high resistance was that it's better to think your tank is empty when it's not (open circuit) than it is to think it's full when it's not.

Well, from other posts I have seen, if you work this out there could be a market for it.

joe_peters said:

Well, from other posts I have seen, if you work this out there could be a market for it.

Click to expand...

I've considered it... it's one of about half a dozen plus neat little electronic gadgets and modules I have kicked around thoughts of building and selling here (as an official vendor of course), though I haven't designed PCBs or written code for any of them yet.

OP - did you ever figure out where the smell was coming from? I don't remember where those vent tubes went to originally on my 96, do they connect to the return line (3/16" steel line) or do they go to breather filters or something?