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Picked up my Sting Gray Sahara at the end of August and am loving it so far. First Wrangler for me. Only problem so far is a Check Engine Light (CEL) that I picked up a couple of weeks ago. I had reseated all the fuses after I bought so I checked the gas cap and it was completely off, just bouncing around behind the closed fuel door. Installed and tightened but no luck on clearing the CEL after a few drive cycles. I had the typical OBDII codes for a gas cap, small and large evap leak. After doing some research I tried all the fixes I could find and learned a few things about the 4XE gas cap that I wanted to share,

1. After some troubleshooting I concluded that the gas cap was not seating tightly enough (I tried all the tricks like a little grease on the o-ring). I tried a "generic" jeep gas cap in the 4XE and it also did not work. Still had the evap codes in even though the new cap was installed tightly. The 4XE gas cap is unique in that it is not vented. Most vehicle gas caps have a spring loaded pressure relief built into cap that maintains the fuel tank pressure at the optimum level (also protects against a vacuum implosion). The 4XE cap does not have the pressure relief feature. It is a solid piece of plastic. Look at the internal end of the 4XE cap and compare to another car to see the difference (and to find another 4XE easter egg). The 4XE fuel system runs at a higher pressure than a normal auto fuel system and the relief feature is built into the fuel system not in the cap.

2. The 4XE cap can also only be inserted in only one position. Most modern gas caps have tabs at the end of the threads that fit into slots in the fuel filler neck. So to get a good seal you have to insert the cap with the tabs lined up with the slots in fuel filler neck before you tighten the cap. The tabs tend to be the same size allowing you to insert at each half turn while you are rotating the cap. The 4XE cap has a very large tab and a very small tab so that you can only install at one point. I'm not really sure why the 4XE cap is different in this regard.

3. Gas caps have a built in over-tightening feature (the clicks) that prevent you from tightening the cap so much that it becomes difficult for you or someone else to open. The clicking sound should be generated when the gas cap threads are at the right torque in the fuel filler neck but it is a fairly crude system. The torque value is set by bending some plastic tabs on two rotating plastic disks that allows the outer cap to rotate separately from the inner cap when the right torque is reached. The clicks are the sound of the plastic tabs slipping and snapping back. I could feel that my cap wasn't getting very tight, it would start clicking almost as soon as I felt any torque when I was tightening. The new generic cap felt much tighter.

4. The last point on the cap is the long tether that is originally installed on the gas cap. The long tether can get caught in the fuel filler neck when you are threading on the gas cap causing a poor seal and CEL. There is a recall for the gas cap that replaces it with a new cap with a shorter tether.

With that info in mind, I made an 7:30 am appointment at my local Jeep dealer and brought in for a new cap. I told them exactly what I thought the problem was, demonstrated the loose cap, and left expecting to get it serviced that day. One benefit of the uconnect vehicle tracking is that I could tell where my Jeep was at the dealer and at 2:00 pm it was still sitting outside. I called and my service rep said they could not get to it that day (why have appointments if they can't even get the vehicle in for diagnosis). I am very impatient with service centers so I said I would come get and just order a new 4XE cap myself. At this point I still had the CEL in.

I picked up my 4XE and brought home and decided to see if I could fix the cap somehow to really confirm that the cap was the problem. I disassembled and tried a few things but no luck. So as a temporary fix I inserted just the inner cap (the threaded portion of the gas cap) and tightened it down. Ran the jeep and checked the codes and was able to clear them this time! Ran the jeep for a couple of days and no problems. Definitely is a bad cap. Ordered a new cap from the dealer ($38 and backordered of course) and am running now with just the inner cap. Luckily I don't put gas in it often!! I will attempt to get the dealer to pick up the cost of the cap but I'm sure it will be too much of a hassle at this point.

Sorry for the long post, but given all the gas cap problems I've seen posted here I figured the information I found might be useful for others.
 

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Great Info and thanks in case I have this problem.

I am in NJ and we have a crazy law (for those that don't know) that we are not allowed to pump our own gas, so an attendant does it (like FULL Serve in other states). I have only put 5 gallons of gas in 2 times (for fuel refresh) but each time let the attendant do it. But I noticed he struggled the last time to get the cap on. I will now be getting out and making sure that I put it back on for now on so they don't unknowingly screw something up!!!!!
 

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Now I gotta go look at my gas cap. Good info, tho. I was wondering why it was so hard to line the cap up when replacing it.

I had mine in for service last week (definitely worth it to get the PCMs reprogrammed) and noticed there is a recall on the gas cap tether. Not sure what it is, but I did notice that it's easy to get it twisted under the cap. They didn't perform that one because the part was on back order.

I also had an appointment 3 weeks in advance and it took 4 days to get the oil changed, tires rotated and 5 PCMs flashed. At least my Max Regen stays on now.
 

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Now I gotta go look at my gas cap. Good info, tho. I was wondering why it was so hard to line the cap up when replacing it.

I had mine in for service last week (definitely worth it to get the PCMs reprogrammed) and noticed there is a recall on the gas cap tether. Not sure what it is, but I did notice that it's easy to get it twisted under the cap. They didn't perform that one because the part was on back order.

I also had an appointment 3 weeks in advance and it took 4 days to get the oil changed, tires rotated and 5 PCMs flashed. At least my Max Regen stays on now.
Sorry, that's not good service. That was a 3 hour job luckily at my dealership. They also did not have the gas cap tether (backordered) and yes, it is because the original is too long and can get twisted under that cap causing it not to seal properly.
 

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Sorry, that's not good service. That was a 3 hour job luckily at my dealership. They also did not have the gas cap tether (backordered) and yes, it is because the original is too long and can get twisted under that cap causing it not to seal properly.
Yeah. Learned my lesson. Getting the loaner vehicle next time so they have skin in the game too.
 

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Now I gotta go look at my gas cap. Good info, tho. I was wondering why it was so hard to line the cap up when replacing it.

I had mine in for service last week (definitely worth it to get the PCMs reprogrammed) and noticed there is a recall on the gas cap tether. Not sure what it is, but I did notice that it's easy to get it twisted under the cap. They didn't perform that one because the part was on back order.

I also had an appointment 3 weeks in advance and it took 4 days to get the oil changed, tires rotated and 5 PCMs flashed. At least my Max Regen stays on now.
Ugh. That's terrible. I'd be livid. Mine was in and out in 3 hrs as promised when they did the updates. Just got a call that the tether arrived so I'm taking it in tomorrow AM.
 

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It happened to me and thank goodness for this thread. I filled up gas and put my gas cap back on. Three days later the check engine light comes on. Found this thread….went to look at the gas cap (see picture) and it looks like I fell for the “long tether” trap. In my rush to close the gas cap, I didn’t notice the tether got stuck inside while I pushed the gas cap closed! Put it back on right, I hope and cleared the CEL. Hope that works.

Vehicle Automotive lighting Automotive tire Wheel Automotive mirror
 

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2021 Jeep Wrangler Rubicon 4xe
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Got this warning on the dash today.
Tire Automotive tire Camera accessory Camera lens Tread

When I looked at the gas cap, I could see that the tether wedged itself between the cap and filler neck. I am 100% sure, that I did not pinch the tether between the cap and the filer neck when I filled it up three weeks ago. I am active on this forum and have read everyone’s problems with their Jeep’s, I am aware of this issue. Could the gas cap tether work its way between the gas cap and filler neck during normal driving?
 

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Got this warning on the dash today. View attachment 2944
When I looked at the gas cap, I could see that the tether wedged itself between the cap and filler neck. I am 100% sure, that I did not pinch the tether between the cap and the filer neck when I filled it up three weeks ago. I am active on this forum and have read everyone’s problems with their Jeep’s, I am aware of this issue. Could the gas cap tether work its way between the gas cap and filler neck during normal driving?
No way.
 

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Picked up my Sting Gray Sahara at the end of August and am loving it so far. First Wrangler for me. Only problem so far is a Check Engine Light (CEL) that I picked up a couple of weeks ago. I had reseated all the fuses after I bought so I checked the gas cap and it was completely off, just bouncing around behind the closed fuel door. Installed and tightened but no luck on clearing the CEL after a few drive cycles. I had the typical OBDII codes for a gas cap, small and large evap leak. After doing some research I tried all the fixes I could find and learned a few things about the 4XE gas cap that I wanted to share,

1. After some troubleshooting I concluded that the gas cap was not seating tightly enough (I tried all the tricks like a little grease on the o-ring). I tried a "generic" jeep gas cap in the 4XE and it also did not work. Still had the evap codes in even though the new cap was installed tightly. The 4XE gas cap is unique in that it is not vented. Most vehicle gas caps have a spring loaded pressure relief built into cap that maintains the fuel tank pressure at the optimum level (also protects against a vacuum implosion). The 4XE cap does not have the pressure relief feature. It is a solid piece of plastic. Look at the internal end of the 4XE cap and compare to another car to see the difference (and to find another 4XE easter egg). The 4XE fuel system runs at a higher pressure than a normal auto fuel system and the relief feature is built into the fuel system not in the cap.

2. The 4XE cap can also only be inserted in only one position. Most modern gas caps have tabs at the end of the threads that fit into slots in the fuel filler neck. So to get a good seal you have to insert the cap with the tabs lined up with the slots in fuel filler neck before you tighten the cap. The tabs tend to be the same size allowing you to insert at each half turn while you are rotating the cap. The 4XE cap has a very large tab and a very small tab so that you can only install at one point. I'm not really sure why the 4XE cap is different in this regard.

3. Gas caps have a built in over-tightening feature (the clicks) that prevent you from tightening the cap so much that it becomes difficult for you or someone else to open. The clicking sound should be generated when the gas cap threads are at the right torque in the fuel filler neck but it is a fairly crude system. The torque value is set by bending some plastic tabs on two rotating plastic disks that allows the outer cap to rotate separately from the inner cap when the right torque is reached. The clicks are the sound of the plastic tabs slipping and snapping back. I could feel that my cap wasn't getting very tight, it would start clicking almost as soon as I felt any torque when I was tightening. The new generic cap felt much tighter.

4. The last point on the cap is the long tether that is originally installed on the gas cap. The long tether can get caught in the fuel filler neck when you are threading on the gas cap causing a poor seal and CEL. There is a recall for the gas cap that replaces it with a new cap with a shorter tether.

With that info in mind, I made an 7:30 am appointment at my local Jeep dealer and brought in for a new cap. I told them exactly what I thought the problem was, demonstrated the loose cap, and left expecting to get it serviced that day. One benefit of the uconnect vehicle tracking is that I could tell where my Jeep was at the dealer and at 2:00 pm it was still sitting outside. I called and my service rep said they could not get to it that day (why have appointments if they can't even get the vehicle in for diagnosis). I am very impatient with service centers so I said I would come get and just order a new 4XE cap myself. At this point I still had the CEL in.

I picked up my 4XE and brought home and decided to see if I could fix the cap somehow to really confirm that the cap was the problem. I disassembled and tried a few things but no luck. So as a temporary fix I inserted just the inner cap (the threaded portion of the gas cap) and tightened it down. Ran the jeep and checked the codes and was able to clear them this time! Ran the jeep for a couple of days and no problems. Definitely is a bad cap. Ordered a new cap from the dealer ($38 and backordered of course) and am running now with just the inner cap. Luckily I don't put gas in it often!! I will attempt to get the dealer to pick up the cost of the cap but I'm sure it will be too much of a hassle at this point.

Sorry for the long post, but given all the gas cap problems I've seen posted here I figured the information I found might be useful for others.
thanks for the run down. My 2 week old 4xe Rubicon just gave me CEL 2 days ago. i tried a code reader but the one I have would not work, which one did you use to read the codes?
 

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Quick update - picked up my new gas cap on Friday and it screws on much tighter than my last one. No CEL with the new cap! Cost me $38. Dealer parts said it was backordered and could take several months but showed up in about a week!
Do you have the link for the newvao to purchase? Having same issue and I want to avoid the dealer appointment lol. Thank you
 

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thanks for the run down. My 2 week old 4xe Rubicon just gave me CEL 2 days ago. i tried a code reader but the one I have would not work, which one did you use to read the codes?
The gas cap only screws in properly when it is oriented a certain way, if you try tugging on the cap, and it comes off, you may have it screwed in wrong.

Here is Chris’s video on this problem.

 

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Picked up my Sting Gray Sahara at the end of August and am loving it so far. First Wrangler for me. Only problem so far is a Check Engine Light (CEL) that I picked up a couple of weeks ago. I had reseated all the fuses after I bought so I checked the gas cap and it was completely off, just bouncing around behind the closed fuel door. Installed and tightened but no luck on clearing the CEL after a few drive cycles. I had the typical OBDII codes for a gas cap, small and large evap leak. After doing some research I tried all the fixes I could find and learned a few things about the 4XE gas cap that I wanted to share,

1. After some troubleshooting I concluded that the gas cap was not seating tightly enough (I tried all the tricks like a little grease on the o-ring). I tried a "generic" jeep gas cap in the 4XE and it also did not work. Still had the evap codes in even though the new cap was installed tightly. The 4XE gas cap is unique in that it is not vented. Most vehicle gas caps have a spring loaded pressure relief built into cap that maintains the fuel tank pressure at the optimum level (also protects against a vacuum implosion). The 4XE cap does not have the pressure relief feature. It is a solid piece of plastic. Look at the internal end of the 4XE cap and compare to another car to see the difference (and to find another 4XE easter egg). The 4XE fuel system runs at a higher pressure than a normal auto fuel system and the relief feature is built into the fuel system not in the cap.

2. The 4XE cap can also only be inserted in only one position. Most modern gas caps have tabs at the end of the threads that fit into slots in the fuel filler neck. So to get a good seal you have to insert the cap with the tabs lined up with the slots in fuel filler neck before you tighten the cap. The tabs tend to be the same size allowing you to insert at each half turn while you are rotating the cap. The 4XE cap has a very large tab and a very small tab so that you can only install at one point. I'm not really sure why the 4XE cap is different in this regard.

3. Gas caps have a built in over-tightening feature (the clicks) that prevent you from tightening the cap so much that it becomes difficult for you or someone else to open. The clicking sound should be generated when the gas cap threads are at the right torque in the fuel filler neck but it is a fairly crude system. The torque value is set by bending some plastic tabs on two rotating plastic disks that allows the outer cap to rotate separately from the inner cap when the right torque is reached. The clicks are the sound of the plastic tabs slipping and snapping back. I could feel that my cap wasn't getting very tight, it would start clicking almost as soon as I felt any torque when I was tightening. The new generic cap felt much tighter.

4. The last point on the cap is the long tether that is originally installed on the gas cap. The long tether can get caught in the fuel filler neck when you are threading on the gas cap causing a poor seal and CEL. There is a recall for the gas cap that replaces it with a new cap with a shorter tether.

With that info in mind, I made an 7:30 am appointment at my local Jeep dealer and brought in for a new cap. I told them exactly what I thought the problem was, demonstrated the loose cap, and left expecting to get it serviced that day. One benefit of the uconnect vehicle tracking is that I could tell where my Jeep was at the dealer and at 2:00 pm it was still sitting outside. I called and my service rep said they could not get to it that day (why have appointments if they can't even get the vehicle in for diagnosis). I am very impatient with service centers so I said I would come get and just order a new 4XE cap myself. At this point I still had the CEL in.

I picked up my 4XE and brought home and decided to see if I could fix the cap somehow to really confirm that the cap was the problem. I disassembled and tried a few things but no luck. So as a temporary fix I inserted just the inner cap (the threaded portion of the gas cap) and tightened it down. Ran the jeep and checked the codes and was able to clear them this time! Ran the jeep for a couple of days and no problems. Definitely is a bad cap. Ordered a new cap from the dealer ($38 and backordered of course) and am running now with just the inner cap. Luckily I don't put gas in it often!! I will attempt to get the dealer to pick up the cost of the cap but I'm sure it will be too much of a hassle at this point.

Sorry for the long post, but given all the gas cap problems I've seen posted here I figured the information I found might be useful for others.
Thanks for the post! I just picked up my 2022 4xe High Altitude a few days ago. 77 miles and this came on. Still have the gas from the full tank the dealer gave me. I'm going to try this! Really appreciate the detail in your post.
 
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