I have an ongoing problem and was hoping some of the experts who may have seen this before might be able to weigh in and provide some advice.

For a long time now (maybe 2.5 years), I've been getting a "Fuel cap loose or missing" warning message on my dash. It always starts the same... I get that warning message in the cluster and then, perhaps a week or two later, a check engine light follows. When I check the code, it's for a minor evap emissions leak indicating a leak equivalent to a hole 0.5-1mm in diameter. I've tried numerous things to fix it. In fact, I think I've replaced every component in the evaporative system at this point. However, after I replace a part and reset the CIL, the car is fine for days or weeks, but the message ultimately comes back. My understanding from reading the repair manual is that the truck only checks for minor leaks every 14 trips (and those trips have to provide the right conditions for checking, so it could be more). That's probably why it takes so long to appear again. Last time, I managed to get the truck in and pass my emissions test before the check engine light came on, so I've got two years to fix this problem before my registration expires now... still, I'd rather get it done ASAP.

The parts I've replaced so far (in the order I replaced them) are:
1. Replaced the gas cap (first thing because it was cheapest and simplest)
2. Replaced the DMTL pump (seems to be a common cause of failure and I had the truck mostly apart to replace a million other things).
3. Replaced the Purge Valve (After the DMTL pump didn't solve it, I took the truck to an indy shop to get smoke tested. They supposedly smoke tested it, though I'm not sure I believe them, and told me I needed to replace the purge valve. I bought one for $400, replaced it, and saw no difference).
4. Replaced fuel flange (This time I took it to a LR dealer. They kept it for a week and told me that I needed to replace the fuel flange. I honestly don't even know what this is, but assume it's the part that connects the fuel filler neck to the gas tank? Crazy expensive... trusted the shop. BUT... didn't solve it)
5. Figured the only other piece in the system was the charcoal canister and that maybe the charcoal had become saturated and may be leading to the error, so I replaced the charcoal canister myself. No change.

At this point, I'm not sure what else to even try with the system. I will say that I have bashed the gas tank in a bit on the bottom while taking the car offroad up in Vermont and I'm wondering if that could have caused a leak somewhere? Still, seems like it would be a large one, not a 0.5-1mm leak if that's the case. Anyway, I'm looking for advice. If you gurus could provide any guidance or anything else to look at, I'd be greatly appreciative. I'm honestly not even sure where to go from here.

 

Have you smoke tested the lines? Leaks like this can be almost impossible to find without actually forcing some visible smoke in there and trying to track it down.

 

Both the Indy shop and the dealer supposedly smoke tested the system and replaced parts that were leaking smoke. Obviously, don’t know how much I believe them...

 

Do you have problems fueling it? i.e. does the pump stop before it is full? I was a known issue with the 2005's BUT I had the same issues with my 2007 SE.

The idea is the filler vent tube is dislodged, causing fuel to flow into the charcoal filter which then breaks down and then contaminates most of the evap lines.

Try pulling the fuel vent lines and make sure they are properly placed, then look at the evap lines for input and output of the canister.

Not saying this is the problem, but it is one place to look

Jeff

Standard Disclaimer: I could be wrong.

 

Thanks. I do sometimes have trouble filling it, but not often. I’ll take a look and review the diagram, but I thought there was some type of filter or check valve in the vent line that would prevent a “leak” from being detected in that piece. Either way, I’ll examine it and report back. Thanks for the suggestion.

 

I’m having the same problem. Have replaced dmtl pump, charcoal canister and fuel cap so far. No dice.

 

Did you ever get to the bottom of this issue? I'm having the same on my 2011 LR4.
Took it into the dealership (which always makes me squirm) - to perform the Recall N623.
Ever since that recall, I have had fuel/evap/check engine related issues...
So far I have replaced: DMTL pump, Charcoal Canister, Fuel flange, O-Ring, Fuel Cap.
Had the fuel tank removed, inspected evap lines, hoses & seals - had the whole system smoke tested about 3 times....
Issue keeps coming back.... But only since the dang N623 Recall....
LR4 had a very happy 12yrs of generally reliable service over 150,000 miles until I took it to the dealer.....

 

If you had issues after the deal had it, I would take it back to them to resolve, for free.