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Thread: 90 mighty max wont run please help!

  1. #1

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    Lightbulb 90 mighty max wont run please help!

    Okay so I recently purchased my third mighty max...a 1990 mighty max 2.4 auto trans. Was told truck originally stopped running said he had to feather the gas to make it go. Truck is getting fuel to motor and is in time. Swapped dizzy with one of my others...I reset dizzy today and it ran for like 4 seconds. Just spitting and sputtering. Now truck does nothing but turn over and back fires like a hit and miss engine but will not run. Any clues? Any and all help will be greatly appreciated! Maybe fuel injectors clogged? Ecm has also supposed to be new.. thanks in advance

  2. #2

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    Check that your distributor is set correctly. I'm not being a tool (well, trying not to be one anyways...) but if you've put it in 'by the book' sometimes you can get this weird, and really freaking annoying, phenomenon where regardless of whether you pull the distributor out and full retard or advance it just barely fires. I got caught with this once and it took over 2 hours of me continuously pulling the thing out and reinstalling it that I suddenly realised wtf was going on. Somewhere an anomaly had taken place when swapping the head over the distributor cam gear was now 'in between splines' and there was no way it was going to fire.

    So I did something that should not have theoretically worked, but it did. I swapped the order of the leads #1 to #4, then hooked the leads up in their standard firing order now using #4 on the distributor cap as #1. And it fired first crank. 2 hours of it farting fire in both directions and me dispersing colourful metaphors at it - and is just jumped to life first turn of the key

  3. #3

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    Has the ecu been rebuilt? Symptoms sound similar to what I went through.
    1990 MM 4x4 3.0
    1991 MM 4x4 3.0 Diamonte
    1994 MM 2wd (work in progress)

  4. #4

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    I set distributor at tdc of #1 I dunno?. And was told ecu
    Was rebuilt. I'm wandering they swapped ecu from a 5 spd truck aren't the computers different? I have another whole 91 that puked oil thru the intake...that I could use for parts just dunno where to start... any way the injectors could be clogged? I think it's getting fire. And getting fuel to motor. He said he once got it running off ether. And timing has been set by a mitsu tech so it's supposedly right

  5. #5

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    Hmm. I 'thought' I had it right too but I got caught out. It was when I full advanced and retarded the distributor and only got a little glimmer of it wanting to fire that I started looking outside of the box for a solution. You got fuel, your ECU has been rebuilt (leap of faith...) and you're still shooting spark. The fact that a manual ECU has been installed in an auto truck may mean a signal from somewhere isn't being intercepted by the ECU and it's throwing fault codes. I know there's a trick to getting an auto ECU to work on a manual optioned engine so I think it would be reasonable that doing the opposite swap requires some wiring or signal input modification. ECU diagnostics is not my thing so I'm really not sure.

  6. #6

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    Yea I started thinking it mite have something to do with that. I played with the distributor also and could tell it was getting somewhere...just sounded like cap lol. I have another good ecu but it's manual also. Guess I'll research some more to see if it's a manual ecu lol. Thanks for the tips @geezer101

  7. #7

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    the ecm will work out of a manuel. it will also work if its from a 1991. post a pick of the ecm case and the inside of it too. it sound like your timing is off. the distributor is extremely tricky to time. theirs a thread on here about it somewhere. spay some starter fluid in the throttle body to see if it will fire up. also check the maf sensor to see if its bad.

  8. #8

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    if the ecm is from a 1991 you will need to change the maf sensor to a 2g style from the 1991-1996 mighty max trucks along with wiring a maf reset wire. check this out if this is the case with the ecm being a 1991. the 1991 ecm will run with the 1990 maf but you will get poor mpgs. http://www.mightyram50.net/vbulletin...ight=1990-1996

  9. #9



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    I'm thinking it's timing. Just because a "Mitsu guy" changed the belts don't mean it's correct. You may want to run through the sticky in the tech section. http://www.mightyram50.net/vbulletin...am-Timing-Mark
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  10. #10

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    Ok guy I bought truck from said he swapped ecu with a running mighty max so dunno year or trans. But I so have a 91 with a good ecu that I know is good and will try to swap and maf sensor. And yea that's what I was thinking timing....sprayed ether in throttle body and does nothing. Just spits and sputters. Like a hit and miss engine backfiring. I'm gonna reset timING again just to make sure. Thanks for all the help

  11. #11

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    Ok so it seems the head gasket is blowed.... got the truck running reset the timing and it cranked right up...checked oil and its very milky...

  12. #12



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    Welcome to the club, lol. We have all seen it or had it. Replacing a head gasket is not a hard job, but there is the more serious problem that always seems to show up on a blown gasket. You need to look closely at the combustion chambers for small cracks that occur between the intake and exhaust valves or the jet valves. It is something that happens very commonly when overheated. There were rumors that Mitsubishi did a bad torquing on that last head bolt and caused some engines to blow head gaskets.
    Inspect the head carefully, if you have Jet valves, this would be the time to install a removal kit for about $20. Be prepared for the worst and if there is no cracks, you slid by it with a stroke of luck.
    The heads can easily be repaired by welding the crack and try not to grind the added metal because this will weaken it and it will crack again. A good welder can fix these in a very short time and they can last forever, in fact they are better with the added material.

    Anyway, keep us posted and we can point you through the repair easily. Heads are also available for about $275 to $350 if I remember correctly.
    After a repair like this, if done correctly it will not do it again if maintained and keep a watchful eye on the temp gauge. Remember, your not The Lone Ranger to have a blown head gasket or a crack on the head. I have replaced mine and the latest one which is #4 has been perfect for many years.

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