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Thread: P1494 Leak Detection Pump-Ignore or Fix?

  1. #1
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    Default P1494 Leak Detection Pump-Ignore or Fix?

    Took the Cherokee to Autozone and got the following code and issue:
    P1494

    Definition
    EVAP leak detection pump pressure switch condition

    Explanation
    leak detection pump switch did not change after solenoid was energized

    Probable Cause
    leak detection pump defective
    open or shorted circuit condition
    solenoid defective

    Now I couldn't find a single hint of importance on the internet, but is this
    affecting my gas mileage or performance?
    Thanks!

  2. #2
    4 Litres of Fury trail rated's Avatar
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    Do you hear a hissing sound coming from the engine compartment? Check the vacuum hoses on the intake manifold, the one that drives the LDP is located on the side of the manifold.

    Also, to retrieve the codes, all you have to do is turn the key on/off/on/off/on without starting the engine. If you have a WJ, an OBD II code will be displayed on the odometer. If you have a ZJ, it will flash the CEL and will give you a Chrysler specific code. Counting flashes is done like this: one flash, short pause, two flashes, long pause, five flashes, short pause, five flashes - would give you 12 and 55.

    This method of retrieving codes works on all 1993-1997 ZJs and 1999-2004 WJs.
    |2001 WJ|4,0L|42RE|NV 242|380000 km|ECE Compliant|
    Внедорожник для Экспедиций и Приключений

  3. #3

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    Quote Originally Posted by Roche View Post
    Took the Cherokee to Autozone and got the following code and issue:
    P1494

    Definition
    EVAP leak detection pump pressure switch condition

    Explanation
    leak detection pump switch did not change after solenoid was energized

    Probable Cause
    leak detection pump defective
    open or shorted circuit condition
    solenoid defective

    Now I couldn't find a single hint of importance on the internet, but is this
    affecting my gas mileage or performance?
    Thanks!
    Does not really effect either one in the short term,it's more of a envirometal thing.The bad thing if you do not fix it will be your check engine light will always be on so you will not know of another issue until your starnded on the side of the road.
    I drive a Liberty,laugh now.

    Sitting on 35's,HP44,RockJock60,and 4:3 AtlasII

  4. #4
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    Loosing manifold vacuum is not good and can throw off a lot of combustion calculation. It also drawing in air after the intack and trottle flow sensors. IMO not a good thing to have knowingly happening. If you clear the code and it comes back assuming there is no manifold leak it may have been a glitch and the solenoid worked again.

    I would take note of the advice from "Trail Rated" and make sure there isn't a leak at the engine.

    2002 Grand Cherokee Laredo WJ 4x4 283,000km Jan. 2014
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  5. #5
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    syracuse, ny
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    I just dealt with this last winter and this summer... You dont say what year/model your Jeep is. That makes a difference, and if you post it we can probably offer more specific advice.

    In any case, trace the vacuum line from the manifold to the LDP, ALL the way. I found a rather large crack, but it was way in the back where the hard line transitions back to rubber. (on the V8 WJs its located behind the drivers rear wheel). I later in the summer also found a crack on the other end of that same hose, where it connects to the pump. I replaced all rubber at that point.

    Other things:

    These pumps, especially the ones mounted in the rear, can get full of water. Deep crossings, or in my case running with the wheel well liner out, can fill them with water. Bad news. I had to replace the pump.

    Replacing the pump if it comes to that - the I6 and V8 model are the SAME pump, but the hose connections are reversed. Its easy to use either for either, but you might have to re-route the vacuum source hose. I got several from a few WJs that were getting parted out, and used the one that looked the best.

    If yours is in the back, search for how to remove the bumper cover, and the fender liner. Its simple once you have the bumper cover out of the way. While I had it out I checked everything over real well, including the vapor canister.

    If you have an I6, I believe its located under the hood and you will have a much easier time..
    1996 ZJ Limited 5.2l, 31" Pirelli Scorpion AT, UC springs with Anthony's BB, Trac-lok, K&N FIPK, and heated seats that work now! (SOLD)

    2002 WJ Limited 4.7l, tow package, moonroof, 06 Rubicon Rims, bone stock but 21mpg!

  6. #6
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    Quote Originally Posted by trail rated View Post
    Do you hear a hissing sound coming from the engine compartment?
    I actually have a video for that, there is a sort of whining sound on acceleration.
    http://youtu.be/09WogMbjEPA

    Sorry I forgot to post info, it's a 97 Laredo I6.

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