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It won't start - looking for a donor MEFI

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  • It won't start - looking for a donor MEFI

    Alright well I finally got my car out of the trailer yesterday to start season prep, i know i know i know, i lagged....
    Anyways, the car hasn't been started since April and has sat in the trailer since. Went to start it yesterday and put the key in the on position and the fuel pump didn't prime. Went to start it and crank crank crank, won't start, no fuel obviously. I check the fuel pump fuse, fine. Fuel pump relay, fine. Ignition fuse, fine. Power relay, fine. Everything powers up no problem. Put a hot wire from the battery straight to the fuel pump, works fine, but the car still won't start with the pump connected straight to the battery. So everything lead to the MEFI. I checked the grounds and they looked good. Checked any loose connections and lightly took the compressor to blow out all sand in the general area. Everything looks okay. So I'm assuming my MEFI took a dump over the summer. Is that a possibility? I bought it used from a guy last year who said it had been sitting on his shelf for years and he had no idea what the track record of it was. The fans don't work on the temp switch so it's kind of had issues since I bought it, but that's been it. So couple questions:

    What else should I take a look at? jc_whipsandjacks had some good feedback and said check the command wire for the fuel pump relay, which i'll take a look at tonight.
    Any other thoughts to help diagnose?
    Any one have a MEFI 4 or 4a lying around that I could borrow to plug in and see if that remedies the issue?
    And if it does happen to be the computer, anyone have a MEFI 4 or 4a tuned for a stock LS1 or an LS1 with a mild cam they'd be willing to sell? Not looking for one tuned for a stroker or boost since I won't be doing either of those with this motor.

  • #2
    The idea of a ground wire growing some corrosion over summer seems more logical that the ECM randomly deciding to to work (not that it not possible) There is a control side and power side to the relay both sides have a ground. Might be a good idea to find the grounds and clean them regardless of how they look
    JC Whips and Shyt For all your whip and Sand Jack Needs
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    • #3
      Originally posted by jc_whipsandjacks View Post
      The idea of a ground wire growing some corrosion over summer seems more logical that the ECM randomly deciding to to work (not that it not possible) There is a control side and power side to the relay both sides have a ground. Might be a good idea to find the grounds and clean them regardless of how they look
      Just took a look at every wire that has anything to do with the functionality of the car starting and everything is clean and connected well. Checked for voltage at all relays and everything looks good except for the wire going from the MEFI to the fuel pump relay. So at this point I’m stumped. Why would it not trigger it to kick on the relay? I went as far as replacing all fuses as well even though they looked fine and checked for continuity on the new fuses as well.

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      • #4
        Originally posted by acefuture View Post

        Just took a look at every wire that has anything to do with the functionality of the car starting and everything is clean and connected well. Checked for voltage at all relays and everything looks good except for the wire going from the MEFI to the fuel pump relay. So at this point I’m stumped. Why would it not trigger it to kick on the relay? I went as far as replacing all fuses as well even though they looked fine and checked for continuity on the new fuses as well.
        I had this happen to a Colorado Sand Truck I was prepping. I installed a new supercharged engine, MEFI and harness and it would not start. I called everyone I knew asking for advice and direction. Even had my buddy come over to doublecheck and it just would not fire up. I talked to CBM and they said to bring the MEFI to them. Chris put it on a car he knew would run and it did the same thing- absolutely nothing. The MEFI had just died. $1000 later I had a brand new MEFI installed and the engine fired right up. Sometimes they just die.

        I have a MEFI 4b that was on a twin turbo engine if you want to try it. Don't know if it'll work for you, obviously it will need a tune, but whatever MEFI you install, your car will need to be tuned.
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        • #5
          Originally posted by L.R.S. View Post

          I had this happen to a Colorado Sand Truck I was prepping. I installed a new supercharged engine, MEFI and harness and it would not start. I called everyone I knew asking for advice and direction. Even had my buddy come over to doublecheck and it just would not fire up. I talked to CBM and they said to bring the MEFI to them. Chris put it on a car he knew would run and it did the same thing- absolutely nothing. The MEFI had just died. $1000 later I had a brand new MEFI installed and the engine fired right up. Sometimes they just die.

          I have a MEFI 4b that was on a twin turbo engine if you want to try it. Don't know if it'll work for you, obviously it will need a tune, but whatever MEFI you install, your car will need to be tuned.
          Might take you up on trying that MEFI you have just to see if it is the computer or not. I'll shoot you a text. Thanks

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          • #6
            I would disconnect the J2 connector on your MEFI; Check to to see you have a constant 12V to J2-1. Next check J2-19, this should get 12V when you turn on the ignition. Everything else the MEFI does (to run the engine) is dependent on Crank Trigger and Cam Trigger signals.
            Pin-outs can be found on Google
            Rick
            No matter where you go.... There you are....

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            • #7
              Originally posted by Dunelover View Post
              I would disconnect the J2 connector on your MEFI; Check to to see you have a constant 12V to J2-1. Next check J2-19, this should get 12V when you turn on the ignition. Everything else the MEFI does (to run the engine) is dependent on Crank Trigger and Cam Trigger signals.
              Pin-outs can be found on Google
              Rick
              Okay will give that a shot. Thanks

              Last night I chased the entire wiring system from battery to MEFI as well as every connector at the motor. Everything looks great. So i'll give that a shot as well as trying another MEFI and see if I can't get this figured out soon.

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              • #8
                Well it was the MEFI. Borrowed another one from @L.R.S. And it started right up. Bummer that I need to get another one but at least it’s easily fixable. Thanks to everyone who chimed in with helpful advice

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                • #9
                  Originally posted by acefuture View Post
                  Well it was the MEFI. Borrowed another one from @L.R.S. And it started right up. Bummer that I need to get another one but at least it’s easily fixable. Thanks to everyone who chimed in with helpful advice
                  Glad you found the problem but sucks you have to buy another MEFI and have the car tuned. If you're going to use CBM call Bruce soon, or I can hit him up for you when I'm there on Monday. I'm also going to Danzio on Monday, but that'll be wee bit more expensive.
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                  • #10
                    Originally posted by L.R.S. View Post

                    Glad you found the problem but sucks you have to buy another MEFI and have the car tuned. If you're going to use CBM call Bruce soon, or I can hit him up for you when I'm there on Monday. I'm also going to Danzio on Monday, but that'll be wee bit more expensive.
                    Yea. Like you said, good and bad news. I’ve got a lead on a MEFI from a guy who just boosted his motor that is willing to sell his 4a that was on his stock LS1. So could be just a plug n play for me. Hoping it’ll work without needing dyno time

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