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  • #76
    Originally posted by basketcase View Post
    Yes as the relays all have been replaced it might be a wiring issue. Each relay has a control side and a load side. If the wiring on the control side gets a high resistance, it could de-energise the relay. I'm not saying its the ignition switch yet. I think as you are getting this fault regularly now, it is time to isolate the circuit causing the problem. Then narrow down the fault in that circuit whether it is a wiring or component issue.

    Yes the coil will be hot at all times. This is only for testing purposes, so just disconnect the wire once you are satisfied the feed to the coil is either at fault or not. After driving the car just pop the hood and disconnect.

    If that does not make a difference, then try bridging the load side of the relays one at a time, pins 30 and 87. That takes the control side of the relay out of the equation (86 and 85) . If the fault stops by doing this to one of the relays you can then diagnose that circuit.

    These are all temporary measures for diagnosis obviously. The cars battery will drain pretty quickly if left on, and risk of burning out a component.
    If a high resistance is causing a relay to kick off, wouldn't I be able to test that with a voltmeter? If so, how many ohms should I see? I have to say running around with a hot coil for an unspecified amount of time doesn't sound like fun. Yes, the issue has been more regular, but I can't say it will show in one drive or in 20.

    Will
    '69 Datsun 2000 Roadster vintage race car (Street driven on a regular basis :taz
    '59 Alfa Romeo 101 Sprint (HUGE project :uhoh
    '88 M3

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    • basketcase
      basketcase commented
      Editing a comment
      You can test the circuit with an ohmmeter for resistance (set your multimeter to ohms) and with each wire isolated from the circuit you should read only a few ohms max. Ideally 1 ohm, but 2 or 3 is acceptable for a longer line. But that does not test the circuit under load. To do that you need to do a voltage drop test. Not easy for a relay circuit. Actually ohms testing a relay circuit is not fun either. Bridging the relay is the first step IMO to see if that stops the problem.

      A hot coil is fine when engine is running. All cars run with a hot coil when driving. Just disconnect the wire you fitted when you are parking it up. Really that's what I would be doing if this were my car.

      Make sure you fit the 12v feed to the 12+ side, not the ground side. The 12+ side is coming from ignition switch.

  • #77
    Is this a different problem? I mean, did you solve the first problem only to uncover another?

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    • #78
      Still the same issue I've been chasing since April. It just has become frequent enough that I've stopped driving the car for the most part. I think I'm now $1400 into new parts for it and the problem is still here, and worse than ever, yet I'm no closer to fixing it. I know its something insanely off the wall and stupid, but I don't have the slightest idea what it might be now.

      Will
      '69 Datsun 2000 Roadster vintage race car (Street driven on a regular basis :taz
      '59 Alfa Romeo 101 Sprint (HUGE project :uhoh
      '88 M3

      Comment


      • #79
        Can you print out the wiring diagrams for the DME in A3, page 1364-4 would be a good place to start. http://wedophones.com/BMWManualsLead.htm

        What may help is connect up 2 test light bulbs inside of the car that you can monitor while driving with thin speaker wires going to terminal 86 of the main computer relay and other bulb connected to terminal 87 of the fuel pump relay.

        The first one will check the power supply through the ignition switch and OBC relay.
        Second will check test power supply out of the fuel pump relay.

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

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        • #80
          At work if I were just to throw parts at a problem like this I would be out of a job. The test bulbs idea is good but time consuming to setup, and watch. If you fit a jumper wire between 30 and 87 on the relay(s), and then drive the car until it either fails or doesn't, then you have isolated the circuit which is causing the issue. That's the first step in fixing the problem, is isolation.

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          • #81
            Originally posted by basketcase View Post
            At work if I were just to throw parts at a problem like this I would be out of a job. The test bulbs idea is good but time consuming to setup, and watch. If you fit a jumper wire between 30 and 87 on the relay(s), and then drive the car until it either fails or doesn't, then you have isolated the circuit which is causing the issue. That's the first step in fixing the problem, is isolation.
            Yes I agree and see what you are saying makes a lot of scene bridge pine 87 and 30 of the main relay that really out, with the light idea shows if power supply is getting to the relay via ignition switch and OBC relay.

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

            Comment


            • #82
              From your description of the symptoms and circumstances under which the engine dies and considering all the parts you have replaced my thoughts/ hypothesis are/is:
              It is caused by an intermittent short between both leads in the engine wiring loom going to the engine coolant temperature sensor.
              Here's why: firstly you have replaced many parts but not the wiring loom and secondly every time it happens the DME gets an input equivalent to " engine at operating temperature" and reduces the amount of fuel it is injecting. For the cold engine this reduced amount is too little to keep it running. the times you manage to get the engine up to normal operating temperature , the difference between the correct readout of the sensor (~200 Ohm) and zero when the wires short out against each other is too small to have a serious effect on the engine running.

              Find the terminals on the ecu that carry the CTS signal and solder a single wire to each of them. Solder a 2000 Ohm resistor between the two free ends of these wires.
              Put the DME connector back on and disconnect the connector at the CTS on the engine coolant rail. Make sure the engine is cold and start it and drive off.
              Whilst the engine warms up it will start running richer and richer since it keeps seeing the 2000 Ohm resistance. As soon as the coolant temp needle starts moving you put the connector back on. The 2000Ohm resistor will still make the engine run richer than it should but less so.

              Instead of a fixed value resistor you could use a potentiometer with a range of 200 - 2000 Ohm and adjust it to lower values according to the temp gauge reading.

              A fellow E30 enthousiast built an interface box for his 55pin DME which allowed him to measure the voltage, current or resistance between each of the 55 pins with the engine running. That way he was able to find an intermittent contact problem in (you guessed it..) the CTS wiring.

              Good luck and please report back your findings.

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              • #83
                If you don't want to make your own interface box, you can search for a OTC-3226-UB-80 breakout box and OTC 3226-15 cable. This will allow measurement of all the I/O on the 35 pin DME used on the S14. eBay is your best bet and sometimes the prices are not too bad.

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                • #84
                  I have mapped the engine coolant sensor resistance vs temperature for use with an aftermarket ECU and the resistance at approx 75 F is 2000 ohms and at approx 175 F it is 350 ohms. I have the entire table if needed.

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                  • #85
                    I haven't had a chance to check anything else. Yesterday I figured since I had my own second ECU that was fully stock, I should put that in and give the loaner back. I unplugged the battery, pulled the loaner, installed my stock one, buttened everything up. Reattached the battery. Car started and ran, so I sat there an was resetting the OBC and the stereo, so about 5 min of idling. And it died. Now it won't restart. Swapped the loaner ECU in, nothing. Tried different relays, nothing. By this point, it was dark, and I had no power, (Thanks PG&E) so I gave up trying to figure it out. I'd guess it had been idling for about 5 min. I don't remember if I could hear the fuel pump running when it died or not. It cranks fine, but does not fire. I tried again about an hour later, and nothing. Something tells me that whatever was on its way out, has finally totally died. (is it possible to install a relay the wrong way? I'm thinking no, but just wanted to check. It was pretty dark when I was swapping relays with a flashlight held in my teeth. I tried wiggling the harness around at the ECU, but this made no difference.

                    Will
                    '69 Datsun 2000 Roadster vintage race car (Street driven on a regular basis :taz
                    '59 Alfa Romeo 101 Sprint (HUGE project :uhoh
                    '88 M3

                    Comment


                    • RAD2LTR
                      RAD2LTR commented
                      Editing a comment
                      Got the car running, popped fuses 7 and 11, one for the fuel pumps (7.5A and a dash/diagnostic port fuse) I can see the bigger fuel pump popping the 7.5 amp fuse, but I don't know what caused the other one to go. I wasn't even driving it. I put my stock ECU back in, started it and let it run till it was warm. I haven't driven it however. Perhaps tomorrow.

                      Will

                  • #86
                    Hel. lo Track30.

                    I had some similar dying issues. Tracked it down to the driver chip in the DME. The driver chip activates the Base of a BJT transistor for the shorting out of the Secondary side of the coil so spark can jump. Literally got stranded a few times. Sometimes it would restart. I had to replace the entire DME.
                    I'm looking for E30 M3 right rear quarter panel. Or entire rear clip for a repair. I've checked Ebay and Dealerships and some dedicated dismantlers. Original owner and not interested in selling. Tks, Angelo 408-206-9663

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                    • #87
                      Angelo,
                      Its not the ECU, I've had 2 different ones (Now 3, haven't tested the 3rd yet) and the problem has persisted. My first ECU does have an issue, but its not the underlying issue since it reappeared with the rebuilt loaner one. The first two had aftermarket chips, an IIGo (my original ECU) a Conforti in the loaner one. The third is a straight, stock ECU.

                      Will
                      '69 Datsun 2000 Roadster vintage race car (Street driven on a regular basis :taz
                      '59 Alfa Romeo 101 Sprint (HUGE project :uhoh
                      '88 M3

                      Comment


                      • #88
                        Originally posted by Angelo View Post
                        Hel. lo Track30.

                        I had some similar dying issues. Tracked it down to the driver chip in the DME. The driver chip activates the Base of a BJT transistor for the shorting out of the Secondary side of the coil so spark can jump. Literally got stranded a few times. Sometimes it would restart. I had to replace the entire DME.
                        I'm looking for E30 M3 right rear quarter panel. Or entire rear clip for a repair. I've checked Ebay and Dealerships and some dedicated dismantlers. Original owner and not interested in selling. Tks, Angelo 408-206-9663
                        Hey Angelo, can you create your own thread please about your wtb quarter panel... You have posted this in many unrelated threads and its getting old.

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                        • #89
                          I finally had a chance to play with the car yesterday. After replacing the fuses, I was able to get it started again, but didn't have a chance to go for a drive. After I got home from work yesterday I ran errands with it and it didn't miss a beat. No hesitations, hiccups or other weirdness. Based on the fact that it ran correctly last night, I drove it to work (35 degrees out this morning) and it ran fine. I'm not going to say that I managed to find two ECUs with the same issue, one of which was supposedly rebuilt, both with different aftermarket chips, but based on the fact that the ECU with the stock chip seems (at this point at least) to be fine, I really have to wonder. I guess time will tell.

                          Will
                          '69 Datsun 2000 Roadster vintage race car (Street driven on a regular basis :taz
                          '59 Alfa Romeo 101 Sprint (HUGE project :uhoh
                          '88 M3

                          Comment


                          • #90
                            Well Will, keeping our fingers crossed that your problem has been solved. This has been quite the journey. If it is the ECUs, it would be good if there was a way to diagnose for future reference.

                            Cheers

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