[herculeesjr]

So I was driving to work early last week, think it was Monday, and the check engine light came on for the first time as I pulled into work, hooked it up to the diagnostic scanner and it showed P0441 EVAP Incorrect Purge Flow. Was going to run a KOER test but didn't have the time as cars started coming in so I cleared the code and parked it. Drove it the rest of the week with no CEL and Sunday I checked pending codes and it showed P0441 so since it was only $25 I replaced the canister purge valve that day since that was the "most common" fix around the web. I hate throwing parts at stuff but it's been a crazy last couple weeks and haven't had time to truly diagnose anything. But at the exact same spot on the road that the CEL came on last week it just came on again today. So as usual the parts throwing technique didn't work. Lol.
Anyways I've checked all the vacuum lines under the hood, some have apparently been rubbing against the engine and wheel wells but none are rubbed through and I've tied them up. I have some dry rotted fittings on the intake that I'm going to replace this afternoon but spraying them, or the vacuum lines, with starting fluid does nothing and I hear no intake leak hissing. So I'm now assuming it's somewhere in the EVAP system itself sadly. But I've never dug much into an EVAP system. Can anyone give me some pointers on where to start with this? This Jeep got it's first serious mudding adventure maybe a month ago, and got 5+ feet of airtime from a hidden ditch on it's stock suspension, so it really got shook up but no damage, and I have a bad habit of "topping off" the tank one extra click at the gas station. If those could be of any help. Other than that, it's a very routine Jeep, as you can tell by the CEL coming on at the same spot as last time.

EDIT: For about a week before the first CEL my mpg steadily dropped from 17-18 average to 14-15, after replacing the canister purge valve it's at 16-17.

 

[herculeesjr]

Bump.

 

[herculeesjr]

Bump

 

[jnicewan]

Evap system leaks can be a real PITA but sometimes it can be something real obvious or easy. Things like a gas cap seal being missing or cracked, vacuum lines leaking, EVAP lines cracked, collapsed or leaking.

I would start with inspecting the fuel cap and o-ring on the cap. Check the EVAP line under the Jeep, locate the vapor lines and charcoal canister and pay close attention to the rubber sections. Locate the emissions decal under the hood and check the vacuum line going to the purge valve and purge valve to the canister.

 

[herculeesjr]

Evap system leaks can be a real PITA but sometimes it can be something real obvious or easy. Things like a gas cap seal being missing or cracked, vacuum lines leaking, EVAP lines cracked, collapsed or leaking.

I would start with inspecting the fuel cap and o-ring on the cap. Check the EVAP line under the Jeep, locate the vapor lines and charcoal canister and pay close attention to the rubber sections. Locate the emissions decal under the hood and check the vacuum line going to the purge valve and purge valve to the canister.

The fuel cap looks okay but since I can't actually test it I may go ahead and replace it, though it did pass emissions testing July 2012. Wouldn't be surprised if it's the original cap and just for the fun of
it I did the math and that means the fuel tank has been opened, filled, closed over 400 times with almost 155,000miles on it. Haha that's a lot of fuel.
I've went over every single line under the hood except for the one that T's off of the cruise control and down into the passenger fender, swear I read what that went to before but now I can't find any information on it, not even the EVAP sticker shows it's there. Going to hopefully put it on a lift today and check that over along with all the undercarriage lines.
FYI apparently it's a hit and miss weather or not a ZJ has a leak detection pump but I'd like to note that mine does have one.

EDIT: Here is a link to my Jeep's album, having pictures of the leak detection pump + purge valve, and EVAP sticker. http://s1284.photobucket.com/user/herqulees/library/1997 Jeep Grand Cherokee ZJ 4L 4WD

 

[herculeesjr]

Got the Jeep connected to the computer today and it tested both the purge valve and LDP, oddly though it refused to test either with a running engine so all I could go by was the good and solid sounding clicks from both when I turned them on and off. So I know that the ECM isn't to blame for more odd electrical issues or any wiring and so far both the LDP and purge solenoid are looking good.
Didn't have enough time to remove the passenger inner fender to trace that mysterious vacuum line but shutting the IAC off with the computer resulted in a near instant stall telling me no vacuum leaks, or none major at the least. Only found one (assuming EVAP) line under the Jeep, running from the top of the fuel tank to the driver side fender where the Haynes manual says the canister is, found no problems but haven't looked in the fender yet. Will look there tomorrow and see if their is fuel in that line.

 

[buttersjeep90]

Got the Jeep connected to the computer today and it tested both the purge valve and LDP, oddly though it refused to test either with a running engine so all I could go by was the good and solid sounding clicks from both when I turned them on and off. So I know that the ECM isn't to blame for more odd electrical issues or any wiring and so far both the LDP and purge solenoid are looking good.
Didn't have enough time to remove the passenger inner fender to trace that mysterious vacuum line but shutting the IAC off with the computer resulted in a near instant stall telling me no vacuum leaks, or none major at the least. Only found one (assuming EVAP) line under the Jeep, running from the top of the fuel tank to the driver side fender where the Haynes manual says the canister is, found no problems but haven't looked in the fender yet. Will look there tomorrow and see if their is fuel in that line.

you shouldn't have to remove the inter fender to trace that line. i have a 97 zj and that line goes under the battery tray to the evap canister. i have a vac leak. mine was intake/exhaust gasket fixed that didnt go away, replaced valve cover gasket and it got better. then traced that line to under the battery tray and the link was all cracked. i've replace almost all of the hard plastic lines with rubber lines seeing at 17 year old plastic is really easy to brake when you accidentally elbow it. the canister will most likely be attached to the bottom of the battery tray and just to let you know you might snap the bolts that hold the battery down. i did even with pb blaster. good luck.

 

[Uniblurb]

you shouldn't have to remove the inter fender to trace that line. i have a 97 zj and that line goes under the battery tray to the evap canister. i have a vac leak. mine was intake/exhaust gasket fixed that didnt go away, replaced valve cover gasket and it got better. then traced that line to under the battery tray and the link was all cracked. i've replace almost all of the hard plastic lines with rubber lines seeing at 17 year old plastic is really easy to brake when you accidentally elbow it. the canister will most likely be attached to the bottom of the battery tray and just to let you know you might snap the bolts that hold the battery down. i did even with pb blaster. good luck.

Did they change the location of the emissions charcoal canister that much on a 97 4.0 compared to a 96 4.0? On my 96 the bottom of the battery tray (passenger side) is a vacuum reservoir and the charcoal canister is located up under the far driver's side of the stock front bumper. Agree about those old plastic vacuum lines becoming brittle and have replaced quite a few myself.

Herquelees, I'd check your charcoal canister closely to make sure it isn't cracked/broken. Especially if you had your ZJ 5+ feet in the air and it might have come down on the front end.

 

[jnicewan]

The charcoal canister is behind the bumper on the LH side, its behind/below the LH headlamp and forward/under the air filter box. The vapor/vacuum lines are in the engine compartment, the vac supply line goes to the intake, the fuel vapor goes to the firewall and follows the fuel supply line back to the tank. Check rubber connections, maybe even disconnect on both ends and blow air through it to verify no restriction.

 

[herculeesjr]

Okay it's been awhile but I finally got a chance to smoke test my Jeep on lunch and smoke started coming out of the leak detection pump filter so looks like I need to find a new LDP. I don't like to buy used and even if I did most ZJ's in pull a parts around here have mostly been stripped but the dealer wants almost $170 and that's crazy to me for the little thing. Anyone have any suggestions for somewhere I can buy one or am I stuck going to the dealer parts counter?

 

[freedom0226]

Ebay

i know you dont like to buy used but then ebay will be your best bet.

http://www.ebay.com/sch/i.html?_trk...ction+pump&_nkw=1997+jeep+grand+cherokee+leak+detection+pump&_sacat=0&_from=R40

and make sure you get one that is confirmed working.

 

[herculeesjr]

i know you dont like to buy used but then ebay will be your best bet.

http://www.ebay.com/sch/i.html?_trk...ction+pump&_nkw=1997+jeep+grand+cherokee+leak+detection+pump&_sacat=0&_from=R40

and make sure you get one that is confirmed working.

Thanks for the link, I've kinda forgotten about the problem because oddly it's gone away, I know it's going to come back eventually, but if it can just pass its emissions test coming up in a couple weeks so I can wait till I actually have the money I'll be happy.

 

[freedom0226]

I also seen a Jeep at the junkyard and saw one still on it let me know if you want me to go pull it