BMW 3-Series (E90 E92) Forum - View Single Post

dpaul · 09-22-2018, 04:38 PM

If moving the wire from the 13mm terminal to the 10mm terminal allows the car to start, then there is nothing wrong with either the wire to the starter, the starter, the solenoid or anything to do with the key circuitry. There is likely corrosion related to the larger terminal or the wire bringing power from the battery to the larger terminal.

Carefully inspect the pictures I've linked below. If you don't have 12+ volts at the larger terminal (after removing nut and wire and carefully wire brushing everything to be free of corrosion), then you have a problem with the wire from the battery bringing current to that terminal.

There are two pieces of wire to be concerned about 1) a short wire from the battery to the thru terminal at the bottom of the batter compartment (#4 in the diagram in the first link). 2) a long wire from the outside of the battery compartment to the engine compartment (#1 in the diagram in the first link). The long wire (#1 in the first link) connects up behind the jump point in the engine compartment (#1 in the second link). The third link shows the wire that goes from the B+ terminal in the engine compartment (#1 in second link) to the starter and then on to the alternator. That's the only one you can actually see with the hood up. Unlikely that one is the problem here. Another simple test you can do: connect positive lead from a jumper cable to the positive terminal of the battery in the trunk. Connect other end of the positive lead of the jumper cable to the jump point in the engine compartment. If the engine starts, than your problem is likely the one I suggested in my first post.

So why did you see 11.7 volts on the jumper point which dropped to 1.4v atter re-connecting the starter cable? Because you put a load on the circuit that has a fairly high resistance due to broken wire/connector or corrosion. In any case 11.7v is not enough. If you have 12.6 at the battery, you must have 12.6 at the jumper point or else there is a problem in that circuit.

https://www.realoem.com/bmw/enUS/sho...diagId=61_1946

https://www.realoem.com/bmw/enUS/sho...diagId=61_1859

https://www.realoem.com/bmw/enUS/sho...diagId=12_1339

09-22-2018, 04:38 PM	#10
dpaul Lieutenant Colonel 654 Rep 1,893 Posts Drives: 2009 E90 335xi, 2011 E93 M3 Join Date: Dec 2012 Location: Boston iTrader: (3)	If moving the wire from the 13mm terminal to the 10mm terminal allows the car to start, then there is nothing wrong with either the wire to the starter, the starter, the solenoid or anything to do with the key circuitry. There is likely corrosion related to the larger terminal or the wire bringing power from the battery to the larger terminal. Carefully inspect the pictures I've linked below. If you don't have 12+ volts at the larger terminal (after removing nut and wire and carefully wire brushing everything to be free of corrosion), then you have a problem with the wire from the battery bringing current to that terminal. There are two pieces of wire to be concerned about 1) a short wire from the battery to the thru terminal at the bottom of the batter compartment (#4 in the diagram in the first link). 2) a long wire from the outside of the battery compartment to the engine compartment (#1 in the diagram in the first link). The long wire (#1 in the first link) connects up behind the jump point in the engine compartment (#1 in the second link). The third link shows the wire that goes from the B+ terminal in the engine compartment (#1 in second link) to the starter and then on to the alternator. That's the only one you can actually see with the hood up. Unlikely that one is the problem here. Another simple test you can do: connect positive lead from a jumper cable to the positive terminal of the battery in the trunk. Connect other end of the positive lead of the jumper cable to the jump point in the engine compartment. If the engine starts, than your problem is likely the one I suggested in my first post. So why did you see 11.7 volts on the jumper point which dropped to 1.4v atter re-connecting the starter cable? Because you put a load on the circuit that has a fairly high resistance due to broken wire/connector or corrosion. In any case 11.7v is not enough. If you have 12.6 at the battery, you must have 12.6 at the jumper point or else there is a problem in that circuit. https://www.realoem.com/bmw/enUS/sho...diagId=61_1946 https://www.realoem.com/bmw/enUS/sho...diagId=61_1859 https://www.realoem.com/bmw/enUS/sho...diagId=12_1339 Last edited by dpaul; 09-22-2018 at 04:48 PM..
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