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Thread: 1994 2.4 No Spark...

  1. #1

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    1994 2.4 No Spark...

    I know there are other threads, but i cant seem to locate the problem...

    I was having issues with the engine randomly turning off. Sometimes it would fire up right away, other times it did not. Now my motor is turning over but is not getting spark from the coil at all. When it was running the timing was 5 degrees BTDC and it was running good (aside from randomly dying). The leads to the coil are getting 12v and when cranking, one of them is dropping. High voltage terminal is showing 11.3 ohms (which is within spec per the haynes manual). I have replaced pretty much everything in this order...

    Plugs
    Wires
    Cap and rotor
    Entire disputer
    Coil (twice)
    J121/LX626 power transitor (ICM)
    Main relays (coming off battery)
    ECM relay
    ECM

    Other parts recently replaced prior to this issue (which i dont think would cause this issue, but more info the better i guess):

    o2 sensor
    EGR
    Fuel pump

    Ive gone over the wiring numerous times and i am afraid im at wits end here. Hopefully someone can help me think of something i have missed?

  2. #2




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    MAF may be dead
    Pennyman1
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  3. #3

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    Quote Originally Posted by pennyman1 View Post
    MAF may be dead
    would that cause no spark in the coil? At this point im willing to try anything, so im going to replace it lol im just curious how the MAF would prevent spark...

  4. #4

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    just unplug the maf and see if it woks. the truck will run rich but should run fine.

    you claimed to have replaced the ecm, was it a rebuild or new? more info is needed here. if you could pull it and take a picture of the inside of it without the cover on so i can see the bare board that would be great.

    to see if its a fueling issue take a can of starter fluid and pull the vacuum hose off the manifold to the brake booster and spay a shot down it, plug the tube back in and see if it fires up. give this a try even tho you have replaced the fuel pump. ive had brand new pumps from napa fail months after replacement.

    try these things first before throwing more parts at it. chances are its a maf or ecm. the 2nd gen trucks weakest link where the ecm-maf-timming belts-front lower control arm bushings. other than those they are pretty solid.

  5. #5

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    Quote Originally Posted by finalfighter View Post
    just unplug the maf and see if it woks. the truck will run rich but should run fine.

    you claimed to have replaced the ecm, was it a rebuild or new? more info is needed here. if you could pull it and take a picture of the inside of it without the cover on so i can see the bare board that would be great.

    to see if its a fueling issue take a can of starter fluid and pull the vacuum hose off the manifold to the brake booster and spay a shot down it, plug the tube back in and see if it fires up. give this a try even tho you have replaced the fuel pump. ive had brand new pumps from napa fail months after replacement.

    try these things first before throwing more parts at it. chances are its a maf or ecm. the 2nd gen trucks weakest link where the ecm-maf-timming belts-front lower control arm bushings. other than those they are pretty solid.
    Pulled the MAF and still no spark. Cleaned it, still no spark.
    It is getting fuel, i pulled a plug and could smell the gas.
    Definitely a rebuild ECU. Pics below:
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    I have traced all wiring for continuity (even the connectors) and everything checks out.

    Im about ready to drive it off a cliff

  6. #6

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    so they rebuilt your old ecm and sent it back to you? its possible the ecm coil driver went bad and it just wont work even if the caps got replaced. if you are getting fuel the distributor should be working. the ecm uses the signal from the distributor to work the injectors and the ignition. sense you are getting fuel its not the distributor.

    it looks like you need a new ecm. grab this one https://www.ebay.com/itm/1991-1992-M...wAAOSwPqleKYmd

    and follow this guide: http://www.mightyram50.net/vbulletin...+ecm+swap+Info

    dam, time sure does fly.

  7. #7

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    i dont what else it could be. if the new ecm does not fix your issue than i would replace the engine bay harness. i dont know if you have access to any pick n pull but they are 40 bucks out the door. plus they are easy to pull out. takes me less than 20 minutes to swap.

  8. #8

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    I don't know what other members' opinions are of those pics but there's a lot of brown funk on some of the soldered joints and the board appears to be scratched up under the caps. Are you able to pull codes from it?
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  9. #9

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    Well I feel dumb now....

    When I went to check continuity on the wires again, the wire between the icm and coil literally fell out when I pushed on it. Took the plug apart and judging by the color I'd say it was holding on by a single strand (enough to give me a signal of continuity, but not to ground a drop the coil to spark). Soldered it back together (I dont have that crimper/pin connector), plugged it in and it fired right up. Just got the timing set and it runs like a champ again. Some many parts over a single strand of wire. Let's put this one in the archives

  10. #10

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    glad it worked out.

    as for the ecm, thats pretty normal on theses when exposed to lots of moisture. it usually does not present a problem. ive seen worse.

  11. #11

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    You can now feel un-dumb for diagnosing the fault and fixing it yourself for next to nothing.
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  12. #12

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    I'm having a similar issue. The disy was changed, new coil, wires and plugs. The coil was throwing some strange voltage. 12v on all 3. So I pulled it and put one off an old ram charger just to try it. It will sputter on starting fluid. Did a comp test, reset disy timing. Then just to be sure to make sure I wasn't 180 out I move it 180. Pulled fuel rail and sprayed carb cleaner through it. Pressure reg won't shift though but it seems stuck closed which should make it run rich if I'm not mistaken. Someone tell me where I went wrong. Also, the truck has been sitting in the woods for about 3 years. It's new to me. And it's about 2 hours away and I can't get it towed. I've hooked a winch to it and uprooted a tree. I've jacked each week up and pulled it and got the brakes free spinning and it still won't budge with a winch. It's a 4x4 and hubs are unlocked, it's in neutral and I'm at my witts end here.

  13. #13

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    The timing belt may have chewed off a few teeth and thrown the timing out - check timing alignment marks. You will need to put the ECM into tune/diagnostic mode. There is a single trace wire in the engine bay that needs to be ground to the body so the ECM will accept new ignition tune settings. The clutch might be frozen (?) or you may need to try to put it in 2WD and roll it back 15-20 ft to disengage 4x4 mode (this is normal for a locked up 4x4)

    A link that will help with tuning your ECM - http://www.mightyram50.net/vbulletin...th-ECM-control

    An online tip to disengaging a locked up 4x4 - https://itstillruns.com/disengage-st...e-2156971.html
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  14. #14

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    So if I've put the new to me ECU in, it won't do anything till I ground the wire to put the ECU into "setup" mode and it takes the new timing?

  15. #15

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    If the ignition parts are solid, the ECU is good and you've got base timing in the ball park then you'll be good to go with resetting the engine tune Hopefully you won't have anything that may be throwing an error code.
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