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M42 Full Rebuild now won't start

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    M42 Full Rebuild now won't start

    Hey guys,

    I'm stuck. We just finished rebuilding my M42 from the bottom up.

    All new gaskets and seals, crank, timing chain and chain guide, all new sensors, DME, AFM, spark plugs, spark plug wires, you name it.

    Stomp test shows all clear.

    Fuel system has been redone. New pump, new filter, good pressure.

    All grounds are checked and solid. All sensors are plugged into the right place. All fuses and relays are good.

    However, the car just cranks and cranks and cranks but won't fire.

    Any idea of how to diagnose and see where we went wrong? We've double checked everything and can't figure it out. Any help would be greatly appreciated!
    Last edited by theTBLACK; 05-05-2016, 09:18 AM.
    Founder
    TheDirtyThirty
    instagram.com/thedirtythirty

    #2
    You probably already checked this, but how about the crank position sensor just above the oil pan?

    Pictures of the rebuild? Good luck!

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      #3
      Check main and fuel pump relays

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        #4
        Check for spark and fuel. Make sure your timing is set correctly and I'm assuming you have compression from the fresh rebuild?
        sigpic
        1991 318is x 2 .

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          #5
          Originally posted by Gkwan View Post
          You probably already checked this, but how about the crank position sensor just above the oil pan?

          Pictures of the rebuild? Good luck!
          Yeah I replaced that with a new one and no dice :(
          Founder
          TheDirtyThirty
          instagram.com/thedirtythirty

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            #6
            Originally posted by Gumby View Post
            Check main and fuel pump relays
            I have fuel pressure and all relays have been replaced :( but I'll double check.
            Founder
            TheDirtyThirty
            instagram.com/thedirtythirty

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              #7
              Originally posted by Fsnow View Post
              Check for spark and fuel. Make sure your timing is set correctly and I'm assuming you have compression from the fresh rebuild?
              Have both spark and fuel. Timing is spot on and compression is perfect. Literally at a loss right now.
              Founder
              TheDirtyThirty
              instagram.com/thedirtythirty

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                #8
                Problem with the ECU maybe?

                Sent from my SCH-R970 using Tapatalk

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                  #9
                  Injector pulse? Fuel off the rail doesn't guarantee it's getting into the combustion chambers. (assuming that's how you tested it). I posted about this in the m20 section too, but my car didn't want to start and I had fuel off the rail but no injector pulse. The injector harness connector was corroded to death with this blue goopy stuff.
                  BMW tech
                  Umass Amherst
                  05 wrx sti

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                    #10
                    Originally posted by nk1221 View Post
                    Problem with the ECU maybe?

                    Sent from my SCH-R970 using Tapatalk
                    I swapped it, still the same problem.
                    Founder
                    TheDirtyThirty
                    instagram.com/thedirtythirty

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                      #11
                      Originally posted by e30onBBSs View Post
                      Injector pulse? Fuel off the rail doesn't guarantee it's getting into the combustion chambers. (assuming that's how you tested it). I posted about this in the m20 section too, but my car didn't want to start and I had fuel off the rail but no injector pulse. The injector harness connector was corroded to death with this blue goopy stuff.
                      I tried starting it with ether and still nothing - so i'm ruling out fuel for now.
                      Founder
                      TheDirtyThirty
                      instagram.com/thedirtythirty

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                        #12
                        Man thats weird! Could it be flooding itself out? Wouldn't hurt to also check for vacuum leaks.

                        Sent from my SCH-R970 using Tapatalk

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                          #13
                          Originally posted by nk1221 View Post
                          Man thats weird! Could it be flooding itself out? Wouldn't hurt to also check for vacuum leaks.

                          Sent from my SCH-R970 using Tapatalk
                          I don't think so :( I also replaced all hoses and vacuum lines haha.
                          Founder
                          TheDirtyThirty
                          instagram.com/thedirtythirty

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                            #14
                            Damn haha! Is it throwing any codes during a stomp test?

                            Sent from my SCH-R970 using Tapatalk

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                              #15
                              Originally posted by nk1221 View Post
                              Damn haha! Is it throwing any codes during a stomp test?

                              Sent from my SCH-R970 using Tapatalk
                              Codes run all clear!
                              Founder
                              TheDirtyThirty
                              instagram.com/thedirtythirty

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