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    Electrical nightmare and I am out of ideas

    Hey team,
    Just wanted to start of by thank you to all the contributors. you guys/gals made it keeping this car much easier.

    Background story, e30 07/1987 convertible cabriolet bought by my father in law with 4 miles on the title. Still have the original title.
    The car was in rough shape. It survived Sandy and sat outside for about 12 years until it was gifted to me.

    When i got it was dead as door nob. I replaced the starter, Injectors, new bat, all new filters all the basics and was able to start it!
    She did not sound very happy when she ran, almost like the belt was stretched/skipped a tooth.
    I wanted to get the car back to its original glory.
    Kept the engine in but removed the head, replaced all the bolts, valve seals, cams seals, crank seal, oil pump seal, polished the head up really nicely
    cleaned all the valves the whole 9 yards.

    Put everything back in and the following is happening.
    She Cracks very strong sounds very health! much better then before.

    No spark no fuel.
    Did the 30/87 short on fuel, strong! pressure at close to 40psi

    Noticed the following,

    The main relay buzzes, which means there is a short somewhere.
    Connected OHM meter to the body and positive terminal getting 1.2 ohm which mean closed circuit! not good.
    Pulled out all the relay and i mean all, Still and 1.2 ohm

    When I pulled the fuses fuse 6,8,10 dropped the OHM to 40ohms body to positive (bmw states it should say 1000ohm or 1k ohms, normal operating)

    Fuses 6,8,10 - means something in the back is going.

    So i did some investigating. all the wires seem good in the back by the taillights.
    i shook the cables in the back to see if i can stop the close loop beeping on the multi meter, nothing changed. the ominous beeping still haunts me.
    Disconnected the rear lights both left and right since in figured the issue was causes. still beeping 1.2 ohm.
    Disconnected all the sensors, oil pressure, cold start sensor, water temp, Electro fan. still beeping 1.2 ohm.
    Disconnected ECU main plug and the DME main plug, - still beeping 1.2 ohm
    Disconnected the reverse backup lamp - you guested it still beeping 1.2 ohm
    Disconnected the c101 - still beeping 1.2 ohm

    Started is connected, Alternator still connected

    Noticed a huge tear in the positive to the coil by the battery - so i cut it, re-soldered and heat shrunk it, even re-soldered together the shielding around the positive cable.

    After test again I have the multi-Meter going from the large positive which goes into the fuse box and the body/engine. Still getting 1.2 ohm and beeping.


    Everything is still disconnected hanging out.
    i'm at a loss right now.
    I was planning changing some of the connectors for brake pad and things like that, since all the connectors are crumbling in my hands. I do wan to make sure the car runs before i start making a new parts of the harness.

    Any recommendations?
    and just want to say thank you in advance.


    #2
    I would check the crank position sensor.

    The ECU will only kick the pump on if a signal from the CPS is received.

    No spark/no fuel is a common symptom of a bad CPS or damaged wiring.

    In some cases, after a timing belt is done, the wiring for the CPS won't be tucked back behind the clip that secures it away from the water pump belt and it's possible for it to be cut by the pulley or belt.

    Maybe you forgot to connect it all together? The connector is underneath the OBD0 port and I believe the plug is interchangeable with the other plug that is fastened to the same bracket. So, if you had swapped the plugs, the car wont start since there is no signal from the CPS.
    Current Collection: 1990 325is // 1987 325i Vert // 2003 525i 5spd // 1985 380SL // 1992 Ranger 5spd // 2005 Avalanche // 2024 Honda Grom SP // 2024 Yamaha XSR700 // 2024 Jeep Gladiator Rubicon

    Comment


      #3
      Originally posted by MrBurgundy View Post
      I would check the crank position sensor.

      The ECU will only kick the pump on if a signal from the CPS is received.

      No spark/no fuel is a common symptom of a bad CPS or damaged wiring.

      In some cases, after a timing belt is done, the wiring for the CPS won't be tucked back behind the clip that secures it away from the water pump belt and it's possible for it to be cut by the pulley or belt.

      Maybe you forgot to connect it all together? The connector is underneath the OBD0 port and I believe the plug is interchangeable with the other plug that is fastened to the same bracket. So, if you had swapped the plugs, the car wont start since there is no signal from the CPS.

      Appreciate the response.
      Sensor reading 520 ohm, within the BMW 10% spec. I though it was an issue as well.
      I replaced it with a brand new one when i was just starting out. I think it is damaged cables. Not sure where to start looking though

      Comment


        #4
        What have you replaced relay wise? did you do a fuel pump replacement? If so which pump did you use? Are all your grounds good? What codes are showing during a stomp test? Could be your ignition switch going bad. Do you have a 13 button OBC? if so it might cutting fuel because of the disable code.

        88' Seta 2.7i Zinno

        https://www.r3vlimited.com/board/for...430-my-88-seta

        Comment


          #5
          If you think you have a short check the strut tower grounds and positive wires on the firewall distribution block. They are long enough to be swapped and BMW used brown for ground and black for positive, which confuses people. One of those wires being swapped can cause a buzzing relay, I have seen it before, another burns the harness up.

          IG @turbovarg
          '91 318is, M20 turbo
          [CoTM: 4-18]
          '94 525iT slicktop, M50B30 + S362SX-E, 600WHP DD or bust
          '93 RX-7 FD3S

          Comment


            #6
            Originally posted by It's Soda Not Pop View Post
            What have you replaced relay wise? did you do a fuel pump replacement? If so which pump did you use? Are all your grounds good? What codes are showing during a stomp test? Could be your ignition switch going bad. Do you have a 13 button OBC? if so it might cutting fuel because of the disable code.
            1. Relays - I pulled out all the relays looking for the short
            2. No Fuel pump works well when you short 30/87 on the middle relay
            3. All Grounds have been cleaned and seem good according to the multi meter.
            4. Could be your ignition switch going bad - i didnt know they go bad, do they have a ground in them that could short? and cause a buzzing relay?
            5. 13 button OBC - yes i have. Have not checked it because there is a short through out the system​.

            Comment


              #7
              Originally posted by varg View Post
              If you think you have a short check the strut tower grounds and positive wires on the firewall distribution block. They are long enough to be swapped and BMW used brown for ground and black for positive, which confuses people. One of those wires being swapped can cause a buzzing relay, I have seen it before, another burns the harness up.

              This is interesting. I am going to check that in an hour or so.
              I believe I have 3or4 wires coming into the positive terminal red w/black shielding.
              1 Negative going straight to the tower. and then i have a wrapped bundle of black from the firewall which is connected to the valve cover.

              Comment


                #8
                My car is newer than yours and modified, a '91 318is with a '91 325i convertible engine and harness in it, but this is what I have:

                Click image for larger version

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                Ignore the white wire on the top terminal in picture two, it's an add-on. There are no wires going to my valve cover, It has been too long since I looked at a stock car to recall if there are supposed to be any.

                IG @turbovarg
                '91 318is, M20 turbo
                [CoTM: 4-18]
                '94 525iT slicktop, M50B30 + S362SX-E, 600WHP DD or bust
                '93 RX-7 FD3S

                Comment


                  #9
                  I'll echo the question Mr. Burgandy raised. This issue is not what the CPS reads but whether you plugged the CPS in correctly. There are two connectors side by side that look exactly the same. Swap them and see what happens. Easy to do and rules this out. I made this mistake once when trying to trace a no start (with no spark and no fuel after testing all other options). My old CPS would read fine but had a wire short where the insulation had worn through. I replaced the CPS with a new one and connected everything back up and still no start. Just on a hunch I swapped the plug connections since I had been moving things around and forgotten to mark which connectors went with which plugs. Car fired right up.
                  1990 325i: slippery slope from DD/DE car to SE30/ITS
                  1991 318is: raw DD
                  2004 330i zhp: civilized daily driver

                  Comment


                    #10
                    Look into the 13 button OBC. I know it can cause problems.

                    88' Seta 2.7i Zinno

                    https://www.r3vlimited.com/board/for...430-my-88-seta

                    Comment


                      #11
                      Originally posted by Boris3 View Post
                      I'll echo the question Mr. Burgandy raised. This issue is not what the CPS reads but whether you plugged the CPS in correctly. There are two connectors side by side that look exactly the same. Swap them and see what happens. Easy to do and rules this out. I made this mistake once when trying to trace a no start (with no spark and no fuel after testing all other options). My old CPS would read fine but had a wire short where the insulation had worn through. I replaced the CPS with a new one and connected everything back up and still no start. Just on a hunch I swapped the plug connections since I had been moving things around and forgotten to mark which connectors went with which plugs. Car fired right up.
                      When i took the car apart originally i marked up identical cables with different color masking tape to ensure i connect those back up.
                      just for kicks, i swapped them and tried again.
                      Relay still buzzing not spark no fuel.
                      I think there is a short something rubbed throw or cut a positive.

                      Comment


                        #12
                        Originally posted by varg View Post
                        My car is newer than yours and modified, a '91 318is with a '91 325i convertible engine and harness in it, but this is what I have:

                        Click image for larger version

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                        Ignore the white wire on the top terminal in picture two, it's an add-on. There are no wires going to my valve cover, It has been too long since I looked at a stock car to recall if there are supposed to be any.
                        I will send a picture of that i have on the positive and negative terminal in a few. cleaning up. I have strong suspicion it something in the back of the car.
                        When i pull fuse 6 ohm drop to from1.3 - 34 ohms
                        and when i pull 8 goes to 44 ohm

                        Comment


                          #13
                          You guys are going to laugh....
                          3rd brake light.
                          I disconnected it. Short went away.
                          Connected all the cables. started right up.
                          WTF is going on with the 3rd light!
                          anyways, We are done!
                          Have some housekeeping to do first. Mission for 2022 complete.
                          Thank you for all the help team
                          Last edited by cyrillink; 12-31-2022, 09:29 AM.

                          Comment


                            #14
                            Not sure if you're aware of this site, but you can grab the Electrical Troubleshooting Manual for your car/year, which REALLY helps with troubleshooting:


                            Save a copy in case the site dissapears.
                            sigpic
                            1987 - 325i Convertible Delphin Auto [SOLD], 325i Convertible Delphin Manual [SOLD]
                            1989 - 325i Convertible Bronzit m30b35 swapped [SCRAPPED], 325i Sedan Alpine Auto[DD]
                            1991 - 325i Coupe Laguna Manual [Project], 535i Sedan Alpine [SCRAPPED]

                            Comment


                              #15
                              Originally posted by cyrillink View Post
                              You guys are going to laugh....
                              3rd brake light.
                              I disconnected it. Short went away.
                              Connected all the cables. started right up.
                              WTF is going on with the 3rd light!
                              anyways, We are done!
                              Have some housekeeping to do first. Mission for 2022 complete.
                              Thank you for all the help team
                              3rd brake light eh? Wouldn't have guessed that one.
                              I guess your hunch about something in the back of the car was correct.

                              Comment

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