Replacing WJ leak detection pump - North American Grand Cherokee Association
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Old 08-12-2009, 06:14 AM   #1
wjcando
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Default Replacing WJ leak detection pump

I've had an intermittent EVAP system error message for months, traced probable cause to the leak detection pump that's squeezed between the left headlight and the airbox on a wj. Picked up the assembly at a junk yard, looked a lot newer than mine, worth a try. It was easy to get out of the donor because bumper, grill and other stuff was already gone.

Factory svc manual says the unit is removed/reinstalled by removing only the airbox first. Did that, plus pulled the headlamp out, plus my rig has no fender liners or washer bottle to get in the way. Even then, it was a PITA to remove the old one (using vise grips on the wrong side of the bolt, where the threads extend into the wheel well).

I've only been able to put back two of the three bolts (8mm hex head). The space is so tight, I just can't get to the bottom bolt.

Anybody done this replacement before? If so, got any suggestions on technique and tool?

Otherwise, I'll probably just wait until I tear up the front to install an aftermarket bumper.
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Old 10-14-2009, 04:59 PM   #2
01_WJ_Grand_Cherokee
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First I have to chuckle. I had to replace my leak detection pump due to a check engine light that pointed me to large leak. Fortunatly my buddy had a smoke machine and hooked it up an found where the leak came from. Now there is no real technique to it. I recommend at least two people when it comes to the bolts for the air filter. But using smaller tools and adjustable angles to work best. I bought my pump straight from the deal including hose and filter. Still got a good deal with military discounts. So let me know if you need to know anything else.
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Old 10-17-2009, 07:05 AM   #3
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Update. I was in a junkyard several months ago and found a WJ with a LDP that looked newer than mine. So I pulled it, paid maybe 16 bucks, took it home and put it on my rig. Problem solved for about three months. This week, the check engine light comes back with the same code. Smoke machine next, I guess.
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Old 10-17-2009, 11:32 AM   #4
01_WJ_Grand_Cherokee
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What code are you actually getting? I would recommend, presuming the code is for a large leak, getting a smoke machine to see where the leak is at. You get OEM parts for a little bit cheaper at www.moparpartsamerica.com They pretty much got every OEM part for the WJ. Also on the website i just mentioned gives an exploded view of the componets other than the LDP that are part of the emission system
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Old 10-18-2009, 07:45 AM   #5
wjcando
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Thanks.

I'm getting P0441, Evap purge flow monitor, insufficient or excessive vapor flow detected during evaporative emission system operation. Not a big deal I guess, but enough to fail the VA emissions test if it happens to kick in at the wrong moment during inspection.

Tried replacing fuel cap months ago, tried checking all evap related hoses under the hood, had a friend run a scan and he said it pointed to the LDP. So when I found one cheap in a junkyard, I thought I'd give it a try. Worked like a charm -- for about 2 months.
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Last edited by wjcando; 10-18-2009 at 07:49 AM.
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Old 10-18-2009, 08:47 AM   #6
01_WJ_Grand_Cherokee
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Well I looked up a few things and I would say to change the purge valve at this time since you are getting that code. You can get a new one for about 26 bucks at the website I mentioned before. I would also recommend changing the purge valve isolater as well and thats around 8 bucks on the website as well. Not sure of the year on your WJ but these are the prices for 99 to 01. If you go to website go under emissions and click on filter and there should be a view illustration button and that will show you the emissions related components.
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Old 05-05-2010, 12:27 PM   #7
dufunnel
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What year WJ had the leak detection pump in the engine compartment? My 04 is behind the driver's side rear wheel right by the gas tank. See TSB 25-001-02a. Anyone know if the LDP beeps on a failure? I've seen several problems reported around the web of a beeping after startup for about 5 minutes coming from the driver's side of the gas tank area. I've been having this beeping intermittently, and I also have the large leak DTC. I'm wondering if anyone has encountered this condition so I might limit my diagnostic time.
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Old 05-05-2010, 09:46 PM   #8
01_WJ_Grand_Cherokee
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Default LDP Location

I know for a fact that the 1999-2001 has the LDP in the engine compartment. I do know that they eventually relocated like you said to the rear. No the LDP does not make any sounds, esentially its a solenoid that opens and closes. When this malfunctions it will cause your check engine light to come on. Usually the code set is a large leak detected. To further confirm that the LDP is leaking is hooking up a smoke machine as I had done which confirmed my problem. Also another good website with a wealth of info is wjjeeps.com
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