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no start (have fuel, spark, + injectors getting 2v with ignition??)

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  • no start (have fuel, spark, + injectors getting 2v with ignition??)

    Hi all,
    I've been using this e30 wiki to resolve a no-start condition: https://www.e30zone.net/e30wiki/inde...s_Troubleshoot

    so far:
    - fuel is reaching the fuel rail (with new pump and filter)
    - spark plugs are sparking (confirmed by removing/grounding plug during crank)
    - injectors are not firing (plugs dry after cranking)
    - main/dme relay confirmed working with an ohm meter and 12v source
    - injectors cycle when provided with 12v
    - reading signal to injectors: I read 2v at the individual injectors when the key is in the ignition position, then, when cranking, I still read 2v across the individual injectors (was looking for a 12v pulse, that is what I should be reading correct? I'm using a cheap analog volt meter).

    Looking for guidance on where to look next, should I take apart the glove box and check the ecu? how do you check the ecu, is there a common fault? ///ummm

    thanks

    edit, posting this ecu/ DME pin-out for ref. in case it might help someone in the future, pin 14 & 15 are for injectors: https://s14net.vbulletin.net/forum/s...n-out-accurate

  • #2
    can someone confirm that if the CPS malfunction there should be no spark AND no fuel correct?

    Comment


    • #3
      Have you checked the trigger sensors?

      Comment


      • #4
        Is a trigger sensor the same as a crank positioning sensor? I have not checked the crank positioning sensor because I think that a malfunctioning sensor will cut fuel and spark.

        Comment


        • #5
          When was this engine running last? What got you to where you are? This info will help with diagnosis.

          Comment


          • #6
            Engine was last run approximately 3 years ago (I am told from previous owner), flushed out old gas & put new, replaced outboard fuel pump and fuel filter, fresh battery, replaced a few cracked engine hoses.

            Plugs look a little cruddy but still sparking fine.

            Everything I've done so far is in the first post, just pulled the dme to check the solder joints.

            Comment


            • #7
              Originally posted by BMWi4 View Post
              Is a trigger sensor the same as a crank positioning sensor? I have not checked the crank positioning sensor because I think that a malfunctioning sensor will cut fuel and spark.
              Yes, they are the same.
              not sure if they cut both. Someone can probably verify that.
              But they are failing now and then.
              They can also be switched, if someone has touched them or the wires of course..

              Comment


              • #8
                Pulled DME to verify enerything looks ok in there, the injection pins from #14 & 15 looked solid with no cracking which I've read sometimes happens

                Comment


                • #9
                  Hi,
                  The fact that you are measuring 2v at the injectors with the key in the on position is a concern, probably pay to recheck that just to make sure.

                  The injectors are supplied with 12v from the main relay and then earthing is controlled inside the DME to give pulse widths.

                  I suggest charge the battery, check the fuse-able link at the + battery cable in the trunk it feeds power to the DME and fuel pump relays behind the coolant tank.
                  Remove the plastic panel behind the coolant tank check voltage supplied to the DME relay and check DME relay terminal 87 voltage when cranking.

                  Dave.






                  E30 M3 1987
                  Mini Clubman GT
                  BMW E36 323 Msport
                  Toyota Corona
                  KTM 200EXC
                  Honda CB50 (1979)

                  Comment


                  • #10
                    Given the time it sat, possibly stuck injectors?

                    There’s a cheap tester you can buy on eBay (I’ll need to search for the link), or you can swap in a spare set, or send yours out for cleaning.

                    Good luck.

                    -Ken

                    Comment


                    • #11
                      Originally posted by 808M View Post
                      Given the time it sat, possibly stuck injectors?

                      There’s a cheap tester you can buy on eBay (I’ll need to search for the link), or you can swap in a spare set, or send yours out for cleaning.

                      Good luck.

                      -Ken
                      I was able to bench test and do a basic cleaning with this tester. You'll need to adapt some wiring. They have adapters to plug into an aerosol cleaning can but before they were available, I was able to pool cleaner in the top of the injector and pressurize with a compressor and then trigger the tester. For testing, just trigger and listen for the clicking.

                      If you are going to clean them, get some injector screens off of eBay.

                      Here's the tester: ALLOSUN Injector Tester Auto Fuel Injector Tester 4 pluse modes 12V Diagnosis

                      Sorry, couldn't get the link to work.

                      Comment


                      • #12
                        Dave @nz the battery is like new and sits on a trickle charger. Voltage to dme relay confirmed 12v hot, does this rule out the fusable link? I will check injector voltage again. Agreed 2v is very weird...

                        808M thanknyoubfor the link, I tested the injectors with a 12v source and they all activate ok, not stuck. While they are out of the car, I am sending them to get cleaned with new screens, pintles and o-rings, there's a diesel shop nearby that does good work

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                        • #13
                          If you have 12v or better at terminal 30 of the main relay while cranking all good, if not look towards cracked fusable link in trunk, otherwise look at my previous post.

                          E30 M3 1987
                          Mini Clubman GT
                          BMW E36 323 Msport
                          Toyota Corona
                          KTM 200EXC
                          Honda CB50 (1979)

                          Comment


                          • #14
                            Dave @nz Thanks, I'll double check the main relay terminal 30 while cranking and report back. (Note, when removing the main relay, terminal 30 and 86 show 12v hot as they should).

                            Just to confirm how to test, please let me know of this is right: with the main relay plugged in, terminal 30 to ground should register 12v on volt meter while cranking?

                            Comment


                            • #15
                              If you can leave the relay plugged in and back probe 30 make sure 12v when cranking, I recall one forum member had a cracked fuseable link and the 12v would disappear at times.
                              The wiring manual shows the main DME relay has two 87 terminals one powers up the DME other 87 terminal powers the injectors and feeds the fuel pump relay.

                              So if you have 2V at the Injectors you have a problem, back probing is best practice that way you can check voltage drop across the relay contacts.




                              E30 M3 1987
                              Mini Clubman GT
                              BMW E36 323 Msport
                              Toyota Corona
                              KTM 200EXC
                              Honda CB50 (1979)

                              Comment

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