Hello,

I have a 2002 XJ8 with 125K miles and started getting a periodic "Check Gas Cap" message coming up and an occassional P0455 code being tripped on my car. I did the easiest thing first and got a new gas cap from the dealer and it did not do much to stop the codes. I have been reading some posts about this in the forum and can't really determine if it is caused by the Canister Close Valve or the Purge Valve. Should I just buy both and replace them or is this typically caused by one or the other? I was going to try to fix the problem before I had to go through the hassle of a dealer smoke test.

Thanks for any help on this issue.

 

From my experience, just get both and install both. I lost a customer in a 2000 XK when I could not find the leak coming from the purge valve soon enough. The last visit was the final repair. I found a sliver of metal causing the leak. The close valves can get corroded as well and since they don't close all the way during the EVAP test, a leak code will be triggered. I still have the test harness I made for that XK that had switches and connectors to close off the system without WDS/IDS.

 

I was taking a look at the EVAP system under the car and did notice the vapor tube going from canister to canister was rusted. Is this an item that should be automatically replaced? Is it a dealer only item?

 

Hmmmm, The rust on that pipe could be through, but it is hard to say. I would say removed it and inspect it but the bolts will break when you take them off and the clips that hold them into the canisters will break too. I have seen those rusted but not causing a problem. If you have some question about the pipe, then just find one at a salvage yard. That pipe is more than likely stupid expensive from the dealer and not a normal item for the aftermarket to make.

 

Thanks for the Help Mark!!!!!

 

I'd been battling The P0455 code for a while myself. I changed the gas cap, still had the code. Then I changed the purge valve under the hood(bonnet). The code soon returned. I stripped off the lining in the trunk(boot) and observed all of the fittings hidden back there and found nothing. Went back to the engine compartment and don't you know a vacuum hose had come undone from my new purge valve. I replaced it with a zip-tie and I'm code free. I'll replace that hose soon as it's probably original and doesn't fit as tight as it should.

 

I believe the "rusty pipe" is the crossover pipe connecting both charcoal canisters. Under the car, behind the rear tires & made of a grade of steel just itching to rust.


Many have a short flexible silver sleeve, (perhaps designed to protect from wheel wash?)


While the exposed pipe is eagerly rust-prone, under that sleeve is worse. It's as if the sleeve was designed to retain road salt & moisture. Even if the exposed length of this pipe is rust-free on your car, move the silver sleeve and examine the hidden section of pipe.


You or your "go-to" shop can replace the canister connector with copper tubing.


Align the ends of your new tubing as closely as possible with the nipples on the canisters.


I believe these pipes rusty and leaking are causing more "small evap leak" codes than most realize.

 

I just fixed my P0455 code on my 99 XJ8. The steps I took were:

Replaced gas cap. Was a waste of money, my old one was fine. I wouldn't suggest doing this unless you see damage on the seal.

I inspected all the hoses. The three that go to the purge valve under the hood near the firewall, and the hoses that go to the fuel tank behind the carpet in the trunk, and then jacked up the car and inspected the hoses coming in and out of the charcoal canisters. I didn't see anything out of place, and though the crossover pipe under the car was really rusty, it didn't have any holes in it. So I took off the purge valve located on the firewall, took it apart, and couldn't find anything wrong with it other than a little bit of dust inside. It was in good shape and wasn't passing air (large leak p0455 code type problem) when I blew in one side of the larger outlet pipes, So I just put it back on and moved on.

So I next I took a look at the canister close valve under the car near the right rear wheel. See attached PDF for what it looks like. I measured 27 ohms across the pins which I thought was low for a valve but as it turns out the new one I bought had the same value. It is attached just by a single T27 screw and a hose clamp on one side. When I removed it and put 12 volts on the pins I didn't hear any click and was able to blow air through it even with power on the pins, which would cause the test to fail I believe? So I replaced it and cleared the code and this was indeed the problem. I did try to repair the old one, but it was too rusty and a new one was fairly inexpensive, I think about 70 dollars off eBay for an original one.

So I hope this helps anyone trying to solve this annoying problem. Take a good hard look at all the hoses and system components in the PDF then go after the Canister close valve first, purge valve second. Really you don't even need to remove them to inspect. Just rig up some way to get 12 volts on the pins and listen for a click on the canister close and on the purge just remove both larger hoses and put a test hose on one side and try to blow air across the valve. You shouldn't be able to or there is an issue.

 

This probably belongs in the Stickies. We will be seeing more and more of these kinds of issues with cars that are much older with lots more miles, rust and corrosion. Repairs way outside the Tech Support Bulletins.