Despres
Tele-Afflicted
Without too much back story, I am trying to get a 1975 BMW 2002 (USA) model running. I am somewhat handy but not a mechanic. It had a fuel delivery issue that I resolved, and still doesn't start so I am now troubleshooting the ignition system. The 2002 model had many iterations, there are dozens of wiring diagrams available online that all say different things, and this particular vehicle has been worked on by someone who apparently had one spool of black wire and one spool of yellow wire, so it is hard to trace the wiring effectively and I am reaching the end of my trouble-shooting capacity. (the guy with two spools of wire also had a lot of blue shrink-wrap tubing, so many sections of wiring are completely hidden behind blue tubing just to make it more of a hassle)
I haven't joined any BMW forums because I am not going to make a hobby of working on this thing, but knowing there are lots of folks on this forum who are pretty knowledgeable about electrical systems in general, I thought I'd post a general question, as I doubt this is very specific to this make and model:
The troubleshooting guides suggest testing the "Black Wire" from the coil, which if color-coded properly would be the low voltage one from the coil's primary winding to the switch on the distributor. The voltage should test 9v (this particular model has a resistor to reduce voltage to the coil). The voltage reads very low, around .7 mV. The trouble shooting guides all say if it the voltage is not there, check for a faulty connection or ignition switch (suggesting there is no power to the coil), but out of curiosity and because it was easy, I checked the connection on the other side of the primary winding, and it reads 9v going into the coil.
So my simple question for those who know how these things are supposed to work: If the current going into the Ignition Coil's primary winding is 9v, and there is zero or near zero current coming out the other side of the primary winding, doesn't that suggest the coil is bad? It seems to me that it would, but none of the guides I've read suggest that could be the issue. It is probably worth noting that the coil got pretty warm in the couple minutes I performed these tests with the ignition on.
I haven't joined any BMW forums because I am not going to make a hobby of working on this thing, but knowing there are lots of folks on this forum who are pretty knowledgeable about electrical systems in general, I thought I'd post a general question, as I doubt this is very specific to this make and model:
The troubleshooting guides suggest testing the "Black Wire" from the coil, which if color-coded properly would be the low voltage one from the coil's primary winding to the switch on the distributor. The voltage should test 9v (this particular model has a resistor to reduce voltage to the coil). The voltage reads very low, around .7 mV. The trouble shooting guides all say if it the voltage is not there, check for a faulty connection or ignition switch (suggesting there is no power to the coil), but out of curiosity and because it was easy, I checked the connection on the other side of the primary winding, and it reads 9v going into the coil.
So my simple question for those who know how these things are supposed to work: If the current going into the Ignition Coil's primary winding is 9v, and there is zero or near zero current coming out the other side of the primary winding, doesn't that suggest the coil is bad? It seems to me that it would, but none of the guides I've read suggest that could be the issue. It is probably worth noting that the coil got pretty warm in the couple minutes I performed these tests with the ignition on.
