Hi all,

I have an '01 XJ and a few days ago it threw a CEL, and upon scanning I had 3 different codes all related to evap system. P0455, P0442, P0456. They are all titled "evaporative emission system leak detected" followed by "(large leak)", "(small leak)", "(very small leak)", respectfully.

A few months ago I had a different evap code pop up (P0441) which I successfully fixed by swapping out the canister purge valve. Since then I hadn't had any trouble until these three codes showed up at once a few days ago. It then dawned on me that the while filling up the truck with gas the last few times, the pump repeatedly shuts off as if the tank is full (when it's not). I think this may be the catalyst for the codes as I had previously smoke tested the system when I was trying to figure out the P0441 code and saw no leaks, and all the lines are pretty new. Therefore I don't think there's actually a leak, I think it has something to do with the mechanism that is causing the fuel pump to shut off while filling.

Hoping to get some guidance if anyone has any ideas on how to fix this. Thanks in advance.

 

check the archives, but i believe there is a long rubber line between charcoal canister and tank, it gets old (if its original), replace it

check the FSM and/or Parts Manual, which is sure to be illuminating

 

The tube running from the breather on the fuel pump down the driver's side frame rail to the engine is made from plastic not rated for gas fumes. Over time, it gets brittle and cracks or breaks. -This is the Most likely reason for the code. Look carefully along the entire tube - If you are lucky, you will see it. If not, a smoke test will tell you where the leak is. You can splice in fuel line to repair it Or Better - replace the entire line

 

Thanks for the response. Not much rust on any of the lines and I previously smoke tested the system when I was trying to figure out the code that popped up a few months ago that I've since fixed, and didn't see any leaks. Going to double check the line that you mentioned but assuming it looks good, my hunch is that it's the charcoal canister itself based on what I've read.

 

Also, why would a hole/crack in that tube cause the gas pump to stop repeatedly before the tank is actually full? Is it just because there's a loss of suction since it's no longer a fully air tight system?

 

I had that same problem. I changed the fuel pump/ filter/ tank vent/ fuel gauge float assembly - and then I could get the tank full - I don't know why, but that worked for me. Make sure that line is good all the way to the charcoal filter and on to the air cleaner. Disconnect the charcoal filter at the inlet and see if things change before you buy a new one. Fuel goes into the tank displaying the air in the tank. The vipers go through the plastic tube to the charcoal filter on to the be burned in the combustion chamber. Air has to get back into the tank as the fuel level goes down. When you start the engine, a vacuum purges the the tubes. If this purge is incomplete (leak in the system) a code will be sent All of this information is in any good shop manual - you should get one

 

Thanks! Just to clarify one thing - what am I disconnecting the charcoal filter at the inlet for? To check the line further or to try filling it up with gas and then drive it while it's disconnected?

 

Disconnecting the filter will cause a CHECK ENGINE code to show - do it BEFORE you go to a gas station to fill up. If you get 17 gal in the tank, then the filter is clogged. The charcoal filter stores the vapers till the vacuum purges it. If it is clogged, air can't escape the tank which could prevent you from filling it all the way - this is very unusual. But it's easier than changing the fuel pump assembly - which is your option if disconnecting the filter makes no difference

 

Oh I see. Let me rephrase, I can get my tank full, but the pump at the gas station just keeps clicking off as if the tank is full. I have to hold the fuel pump handle down lightly and not put the nozzle all the way into the fill hole, and then I can get it full without the thing clicking off every couple seconds.

 

Yes - see if the pump handle works normally when you pull into the station with the filter disconnected

 

Ok got it. Really appreciate the help. Will let you know what comes of it when I get around to doing it