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Thread: Wj wont run

  1. #1
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    Oct 2001
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    Sammamish, WA
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    Icon313 Wj wont run

    So my brothers 2000 WJ (used to be mine) wont start. A while ago some punk kids through bags of flour on it, got everywhere, not much in the engine bay though. They drove it and got it all cleaned off. Then they let it sit in the garage for 2 weeks waiting to get it detailed (to get smell out of inside, yes sunroof was open). Anyway my bro (idiot when comes to cars) left the dome lights on. I got there and battery was completley dead (new battery as of 2 months) no cranking power and about 1.2 volts. Tried jumping it. Eventually got the jeep to crank, start, but would not stay running.

    Observations:

    I can hear the fuel pump pressurize
    After turning over you can rev it pretty good
    It dies almost instantly after letting off the gas (After turning over)
    Charged the battery with a high power charger no difference
    all electrical stuff is off including disconnecting deck and subs/amps
    I replaced the TPS sensor 4 months ago

    So not sure what it could be....Could he have some how killed the computer? Or maybe another sensor....?
    2000 Patriot Blue
    2.5" Anthony's Boost
    265 BFG All Terrains

  2. #2

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    When a battery is that low, it usually does not take a rapid charge very well. It may have gotten up to a high enough voltage to shut down an automatic charger before it was charged. Try charging it on the LOWEST possible settings. Let it charge as long as possible.

    I can give a long explanation but basically you probably still have a dead battery. I wouldn't worry about anything else having been damaged. Even if charging doesn't work, I would still consider the battery as the culprit.

    You may even need to charge the battery, disco the charger and let it sit, charge, disco, etc. Very dead batteries ramp up fast but don't store much energy. The battery is new enough that the plates are probably OK but the water/acid is stratified. You can help it by GENTLY rocking it a few times while it is charging. Just a little is all it takes. Tipping it in each direction a few times is plenty. You only need to raise each side an inch or two to be effective.

    Even if you get it to keep running, you should keep it on a "trickle" charge as long as possible before driving to make life easier on the alternator AND the battery. A very low battery can draw a lot of current for a long time. Much better to get that energy from the wall outlet. The only thing the alternator can do is deliver a fixed voltage. The charger will adjust based on current and will give a much "healthier" charge. This will also minimize the long term impact of having fully discharged the battery. One of the reasons it's "hard" on a battery to be fully discharged is a failure to do this. If you recharge slowly the damage is minimal. If you try to charge it fast, the temp and internal chemistry will encourage deposits on the plates. That degrades both the plates and the acid and becomes more or less permanent damage.
    '02 Overland
    --------------
    '06 Ram 2500 Laramie HD
    Cummins, 4x4, LWB Quad Cab
    48RE w/(Mopar/Jacobs) exhaust brake
    Big, beautiful, and silver...
    [Banks = coming soon]

  3. #3
    Registered oldgeezer's Avatar
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    Oakland, TN, USA
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    I have heard of that (not running unless foot on accelerator after dead battery, not the flour business) happening with ZJs, but don't remember hearing about WJs. The fix for a ZJ is to just drive it a while keeping the foot on the pedal as necessary. The problem clears up fairly quickly. I guess that the PCM has forgotten about things like the IAC setting and has to relearn.
    2001 WJ Limited, 4.7L, Quadra-Drive -- Kenne Bell Supercharger, Stillen Rotors with MM pads (F/R), Addcos (F/R), Kolak 3 inch exhaust with large case MagnaFlow, Rogue Chrome wheels, DRL activated, and Blaupunkt 3.5" dash speakers.

  4. #4
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    I said that i was trickle charging it. I turned it off overnight, but I will let it sit and charge now. I will also try to reset the computer to see if that helps.
    2000 Patriot Blue
    2.5" Anthony's Boost
    265 BFG All Terrains

  5. #5

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    Quote Originally Posted by nick9871
    I said that i was trickle charging it. I turned it off overnight, but I will let it sit and charge now. I will also try to reset the computer to see if that helps.
    If you leave the battery disconnected while it's charging then the PCM will use default values (reset) on the next start up. With a battery that low, the charger, even on "trickle" settings will be generating very high voltages. Personally, I would want to disco the battery to protect the PCM anyway.

    Remember to be reasonably carefull connecting/disconnecting. That battery is creating a lot of Hydrogen gas while charging. Keep the area ventilated and if you can, wait an hour or so after unhooking the charger before you reconnect to the jeep. That is also easier on the "health" issues for both the battery and the PCM.

    DON'T FORGET to check water levels in the battery. You will almost certainly boil away enough to need to add some. Use distilled H20 only. Don't add any of those "magic" additives from the parts stores.

    Just another .02
    '02 Overland
    --------------
    '06 Ram 2500 Laramie HD
    Cummins, 4x4, LWB Quad Cab
    48RE w/(Mopar/Jacobs) exhaust brake
    Big, beautiful, and silver...
    [Banks = coming soon]

  6. #6
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    Falls Church, VA
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    125

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    Quote Originally Posted by oldgeezer
    I have heard of that (not running unless foot on accelerator after dead battery, not the flour business) happening with ZJs, but don't remember hearing about WJs. The fix for a ZJ is to just drive it a while keeping the foot on the pedal as necessary. The problem clears up fairly quickly. I guess that the PCM has forgotten about things like the IAC setting and has to relearn.
    Happened to my WJ just a coupel months ago...where I live, I don't have to drive a lot and so the Jeep went undriven for a couple weeks. Went to start it and hardly anything happened. Tried to jump it, and still nothing. Finally, someone tried pressing the accelerator and puff of smoke puffed out the exhaust and it started, but wouldn't stay running. We let it run for at least a couple of minutes with the accelerator slightly pressed and finally it stayed running. I've been meaning to get a new, premium battery ever since. Its been kinda weak on the startup since then (but always starts).

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