I'm fed up - $50 to anyone who can come tell me why my Yj won't start...

    I don't have the tools, knowledge, or time left to figure this out now.
    Rehash - 1991 4.0L HO FI
    Cranks, but won't fire.
    I have no spark at the coil.
    Replaced Coil and Crank Position Sensor
    I don't have a check engine light at all.


    I unspooled the engine wire harness and couldn't find any breaks,
    splices, or snaps in any of the wires. ECM "looks" good.


    A new harness and/or ECM will cost several hundred dollars so I'm
    looking for some kind of evidence that that is whats wrong with her...
    or if its something entirely different.


    If anyone is up for a challenge I'll pay for it at this point...

    Have you verified the Fuelpump? Lack of pressue may cause the computer to not iniate a spark. I suspect a logical issue, something it telling the ECM its not ready. Try swapping your ECM with another if soimeone can lend one to you.


    Steve $50 please.

    Nobody belongs anywhere, nobody exists on purpose, everybody's going to die. Have a beer.


    Jeeps Owned... 89YJ, 81CJ-8, 99XJ, 93XJ, 00WJ, 05LJ, 22Bronco Badlands !

    Edited once, last by deadfeat ().

    forget the wiring harness...


    If you addressed all spark creating parts...


    check your fusebox AND your ignition module... i had an Ignition mudule go out on my ford and it did exactly what your describing...


    crapped out fuel pump IS possible.. but I'd look at your fuel pump relay 1st ...


    fuel filter may have a chunk of crap in it.......


    does your fuel gauge work? my avalanche's fuel gauge freaked out and said i had 1/2 tank when it was actually empty.... :bang:


    just some suggestions.. I aint no mechanic ..... usually a beer can be of assistance when trying to troubleshoot a problem like that.....




    :rolleyes: If that aint it... its probably the inner spark defribulating generator .. down under the manifold next to the muffler bearing assembly.. or may be low on brake light fluid.... :rolleyes: lol

    Is there any fuel pressure at all? a silly thing to check... the wiring leading to the crankshaft sensor you replaced. On XJs those have melted/shorted out and will mimic the problem of a dead sensor (cranks but not fire, no CEL, no fuel pressure, etc). If you were above the canal I'd swing by with a manual, but sussex county is a bit of a drive right now with my work schedule. good luck.

    Jerry / Whatevah

    2020 Gladiator Mojave - 33" Falken mud tires, LoD side steps, Zroadz bed rack, Quadratec QRC winch bumper, Superwinch EPi 9.0, Kleinn on-board air, Kleinn air horns, lots of lights, Yaesu ham radio with GPS tracker.

    Gone- 2012 JK Rubicon with stuff. Long gone- Long-arm 2001 Cherokee with stuff.

    Check the fuse box
    there is a fuse that will kill the spark located in the main box and in the
    distrubition box near the battey

    >>Lack of pressue may cause the computer to not iniate
    a spark.
    The fuel rail pressurizes nicely and there is a full tank in the back now.
    You can even smell it after a few cranks.


    >>I suspect a logical issue,
    As do which is why this is getting so frustrating.


    >>Try swapping your ECM with another if soimeone can
    lend one to you.
    Working on that, but (apparently) the 91s were a rare breed - before 91
    were carbs, after 92 were a completely different setup.


    >>check your fusebox AND your ignition module...
    Replaced all the Maxi Fuses and fuse box relays - apparently the 91s did
    not come with an ignition module.


    >>fuel filter may have a chunk of crap in it.......
    I am getting fuel at the rail, but when I replace the filter this weekend
    I'll report back.


    >>does your fuel gauge work?
    Partially. When you first start it up it dials over to "F" and gets stuck -
    when I first bought it I thought that was the big issue, it was out of gas,
    but a full tank later and she's still sitting.


    >>If that aint it... its probably the inner spark defribulating
    generator .. down under the manifold next to the muffler bearing assembly..
    or may be low on brake light fluid.... lol
    Already checked the blinker fluid, muffler bearings, and compression on the
    distributor- no effect.


    >>Is there any fuel pressure at all? a silly thing to check...
    Yup - I have fuel and compression.


    >>the wiring leading to the crankshaft sensor you replaced.
    On XJs those have melted/shorted out and will mimic the problem of a dead
    sensor (cranks but not fire, no CEL, no fuel pressure, etc).
    When I yanked the wiring out there was no visbale damage to that line.


    >>Check the fuse box there is a fuse that will kill the spark
    located in the main box and in the distrubition box near the battey
    You mean there's an igntion fuse under the dash as well? I have not replaced
    those relays yet because of the miles of added speaker/accessory wires. I have
    replaced the fuses on both boxes though. Any idea which fuse it would be
    on a normal box?

    Well its good to see ya got a sense of humor about this.. I know how frustrating when it seems like you've tried everything and it still don't work... But IF you aint got it by the time i get off the boat on the 3rd.. I'll be more than happy to swing by and lend a hand.... Your in Susexx right? Im in Milford...



    If your still havin trouble I'll PM ya before i get off work

    check your ground.... the ground to the motor could be loose.... take the postive terminal off for 5 min and let the comp reset and try again


    i had the same problum when i replace my motor... crank... fuel... no spark... apperently i messed up my wirngharness or it went bad on the left side by the distrubitor and coil... it got to the point where i couldent deal with it any more and towed it to the jeep delership... took 2 weeks and 256 dollars... the mecanic had to hand make the left side of the harness replacing each wire.... then it worked.... would of cost me a small fortune but they siad it would of been easy if they got the part and put it in... but the mecanis ordered the wrong one so he had to do it by hand... and i just paid for that days labor.. hehe



    thats all i have

    Quote from Bonkers


    >>Lack of pressue may cause the computer to not iniate
    a spark.    >>Try swapping your ECM with another if soimeone can
    lend one to you.
    Working on that, but (apparently) the 91s were a rare breed - before 91
    were carbs, after 92 were a completely different setup.


    I believe my current one is from a '94 XJ. You want one without the security system (VTSS?).


    [quote author=Bonkers]
    fuel filter may have a chunk of crap in it.......
    I am getting fuel at the rail, but when I replace the filter this weekend
    I'll report back.


    I believe he's speaking about the small 15 amp fuse that sits in the fuse box that houses the relays. Did you check the distributor pick up (cam sensor)? It sits in the distributor. The orange wire that supplies power to the CPS also supplies power to the distributor pick up. Also make sure your CPS is properly spaced from the fly wheel. Some of them can be pretty sensitive. IIRC another thing that have affected starting problems (that I've read about on this board) were the throttle position sensor. But I believe that was with TJs.

    Member since 2000

    Jeeps Owned'79 CJ5:

    Specs-

    - 258 I6

    - '93 Cherokee fuel injection and HO head,

    - bored 30 over

    - with 4x4 cam

    T18 tranny with granny low / Dana 18 t-case

    Dana 44 front and back from late '70s Wagoneer, both locked and loaded with 4.88 gears

    SOA on modified YJ springs with shackle reversa

    Fiberglass tub with 6 point cage mounted to the frame


    2015 Grand Cherokee Limited
    Spec-

    Quadratec Floor mats

    Edited once, last by Slimer ().


    no ground= no turnover... if the block didnt ground, then the starter wouldnt be grounded either... up to u here, but if u really get p/oed, go to a bone yard. p/u an hei distributor off a older 6 cyl gm motor. 50 bucks, new cap for 15 at autozone, and some wire. the hei's are an upgrade anyhow, have the coil IN the cap, and simple to install. swap drive gears from your old dist. one 12 volt keyed power source. at least that would completely eliminate all questions on the spark issue. than u can go from there....

    I'm not sure HEI would work with the EFI because the distributors are different.

    Member since 2000

    Jeeps Owned'79 CJ5:

    Specs-

    - 258 I6

    - '93 Cherokee fuel injection and HO head,

    - bored 30 over

    - with 4x4 cam

    T18 tranny with granny low / Dana 18 t-case

    Dana 44 front and back from late '70s Wagoneer, both locked and loaded with 4.88 gears

    SOA on modified YJ springs with shackle reversa

    Fiberglass tub with 6 point cage mounted to the frame


    2015 Grand Cherokee Limited
    Spec-

    Quadratec Floor mats

    Quote from deadfeat


    You could always have fun blowing uit up!


    you wont do it!!! i double dog dare you


    the coil bolts could be loose and not have a ground... of if its anything like yjrosco's old motor its cover in gallons of oil, crap, and small childern like the ax-5 he gave me

    Quote from yankee19934


    of if its anything like yjrosco's old motor its cover in gallons of oil, crap, +
    and small childern like the ax-5 he gave me


    Actually, its covered in a fine, and really annoying, layer of grease (like
    someone doused the engine bay in WD40) but the motor and TC look
    pretty dam clean - especially considering I'm willing to bet this truck has
    never been washed.


    In fact it was so dirty when I brought her home I thought it was black -
    it wasn't until I washed it and removed the 7# of stickers and posuer
    mods did I even realize it was blue:
    Before:

    After:


    But here are shots of the motor - maybe someone can see something I am missing:
    Coil:

    Top:

    Fuse Box:

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