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    scotsmann7's Avatar
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    Timing rebuilt 4.0 liter jeep engine

    I am having problems starting my newly installed 4.0 L engine (1998 Wrangler Sport). I just replaced the old engine in my Wrangler with a new professionally built long block. The old engine ran fine, except for the bad rod bearing. All wires, lines etc. were carefully tagged and replaced in kind. Fuel is getting to the cylinders, I need to know how to check for spark. I have changed the distributor 180 degrees, in case I was off on TDC with no luck on that change.
    Any suggestions?

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    Re: Timing rebuilt 4.0 liter jeep engine

    Verify this, CKP is properly seated and connected. With the reference mark on the crankshaft damper on TDC, make sure that the #1 piston is on the compression stroke. Verify that the distributor is lined up to fire on #1 cylinder.. Check your firing order..To verify for spark, remove one of the spark plugs and lay it on the engine compartment hooked up to the ignition wire cable. make sure that the base is grounded to the body or engine so that when you crank the engine , you will see if it's got spark coming out.
    Confucious says: Don't eat the snow where the huskies go!

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    Re: Timing rebuilt 4.0 liter jeep engine

    What is the CKP?

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    Re: Timing rebuilt 4.0 liter jeep engine

    If the pulley notch is lined up with "0" on the timing marks is it TDC or could I be off 360 degrees for the compressions stroke on #1 cylinder? I pressurized the cylindeder with my air lance, and at "TDC" and one complete turn ahead it pressurized the same.

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    Re: Timing rebuilt 4.0 liter jeep engine

    Quote Originally Posted by scotsmann7 View Post
    If the pulley notch is lined up with "0" on the timing marks is it TDC or could I be off 360 degrees for the compressions stroke on #1 cylinder? I pressurized the cylindeder with my air lance, and at "TDC" and one complete turn ahead it pressurized the same.
    CKP(Crankshaft position sensor) located on the bell housing lined up on the flywheel.. Yes you could be off on your timing.
    Confucious says: Don't eat the snow where the huskies go!

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    Re: Timing rebuilt 4.0 liter jeep engine

    When indexing the distributor, you actually want the rotor to point just past the #1 terminal when the #1 cylinder is at TDC on the compression stroke. Indexing the Jeep 4.0 HO Distributor this is a good writeup for indexing the distributor. I know it seems simple but a lot of people mess this up, I know I did when I installed my stroker.
    BAMFCJ7

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    Re: Timing rebuilt 4.0 liter jeep engine


    On the 4.0L engine, it should be just slightly before (counterclockwise of) the 11 o'clock position . If not, place a flat blade screwdriver into the oil pump gear and rotate it into the proper position.
    The distributor is correctly installed when:
    • the rotor is pointed at the 5 o'clock position (4.0L engine)
    • the plastic alignment pin (or pin punch tool) is still installed to distributor.
    • the number 1 cylinder piston is set at top dead center (TDC) (compression stroke)
    • the centerline of the slot at the base of the distributor is aligned to the centerline of the distributor hold-down bolt hole on the engine. In this position, the hold-down bolt should easily pass through the slot and into the engine.
    Confucious says: Don't eat the snow where the huskies go!

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    Re: Timing rebuilt 4.0 liter jeep engine

    It turned out the I was 180 degrees off with the distributor. When I positioned the rotor to the 11 o'clock position with the crank pointed to TDC, but apparently not on the compression stroke, it started right up and ran great. Thanks very much for the help!!!
    David

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