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Join Date: May 2014
Posts: 3
1987 (3/87) 325i Convertible Ignition Switch Cont. Tests - Bentley's Manual Issue

Car just quit, it cranks, however, does not start. I am looking at the "BMW" 3 series Electrical Troubleshooting Manual and pages 41 & 42 Electrical System provides a Continuity Tests for IGNITION SWITCH.

Disconnected C200 and at the "Switch" side only three terminals ring okay when the Switch is placed in ON/START and one does not Ring.

The Bentley Manual itself says that there's two Violet wires but, I only see one. Additionally, the manual says there should be a BLACK/YELLOW and I don't see this color except a SOLID BLACK. The actual Switch harness has a Solid Green, Violet, Blue/Green, Solid Brown, Brown/Red and a Brown/Blue.

It has failed the C1 -to- C continuity.

Using the Pin-30 (RED) the solid Green, Violet, and Blue/Green rings with joy in ON/START. The others don't either in ON/START. Should I just replace the IGNITION SWITCH even though the Manual doesn't match the Switch Harness Wire Color Code?

The wiring references in the Bentley manual are a JOKE. Pages 41/42 Ignition Switch Continuity tests. The connector doesn't look exactly like the numbering diagram. Apparently "Terminal 9" black/yellow wire is the start signal that becomes "Terminal 50", but at this wiring connector it is a microscopically small wire size. There's no way that little thing can handle the juice needed to energize a starter solenoid. Did this "Terminal 9" go through a relay or circuit somewhere to become the larger "Terminal 50" wire that triggers the BMW starter?

Its so damn hot in the shop right now its hard to think, and once inside the car with the windows stuck up! you just sweat like mad and can't see within 2 minutes. I wish I could meet the guy that put this Bentley manual together, especially pages 41/42!

Can anyone help, Pretty PLEASE?

Last edited by guapoman2000; 09-02-2014 at 07:24 AM..
Old 08-31-2014, 08:22 PM
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The first thing was to check for FUEL and I completely took out the Aux Fuel Pump underneath the car, driver's side. The pump worked like a champ and while this pump was removed, I did check the voltage at the terminals and didn't receive the specified voltage.

I checked every single FUSE and Relay in all areas of this car. Up to including purchasing brand new relays for the MAIN and Fuel pump. The new ones are hermetically sealed to keep humidity / dirt out and yes, I check every relay outside the vehicle for proper activation and core and relay arms at various Voltages up to and including 12 Volts. I was amazed that the older Relays work very well below 12 Volts and contacts maintain flip action under power very well.

I have checked all cable links for any lose grounds or lose wires along the way to the battery / FUSE box. Since it is a convertible the span to the battery is not that long to reach so, there is not that much to look for as far as cable runs because the battery is in the Engine compartment.

I have replaced the Engine Speed Sensor twice and the one in the car is brand new and measures the specified Ohms that the computer is expecting.

Coil has nothing close to 12-Volts, as a matter of fact it doesn't have the 12 Volts per the manual when it should have it when Battery is connected and most especially with the Ignition Switch. Additionally, I did remove Cylinder #1 Spark Plug Wire and used a Spare Spark Plug (Brand new) and checked for spark and nothing. (While Family Member Cranked Engine)

I have removed the plastic cover in the Glove Box and carefully disconnected the Main Motronic Control Unit Harness and have pin probed all the pins and the ones that do not seem to have 12 Volts are the one going to the MAIN replay since it makes since that the Montronic is the one sending this control but, the Montronic is receiving power, pin 18 (See Diagram, Page 1360-5).

Last edited by guapoman2000; 09-03-2014 at 10:10 AM..
Old 09-03-2014, 06:11 AM
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1987 BMW 325i convertible with motronic 1.1 engine management

The Harness is the large one. (55 Pin)


Old 09-03-2014, 06:22 AM
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OK, first things first: I just barely know jack squat about Bimmers--and less about the 80s 3-series! So anything I can tell you will be pretty much from a "well it looks like the diagrams say" perspective.

With that said, the second post first.
It looks like the diagram is saying that the two 87 pins on the main relay are hooked together inside the relay, so they should be electrically identical. You're showing the same thing on both (0V) which seems to say they are OK. What the relay should do is to bridge together the 30 pin with the two 87 pins when there is voltage across the 85/86 pins. Since 86 (? diagram is fuzzy) goes straight to the battery, you need to check that 85 gets grounded when the key is on.

First diagram:
C and 50 are electrically the same, since they are connected inside the switch. (At least, according to the diagram.) And when you turn the switch to "start" only, both of those should be bridged to 30 (and to C1, which is connected to 30 inside the switch).

So now you need to figure out which wires correspond to what in the diagram. I think it's pretty safe to say that your red wire is the same as the red wire in the diagram, as it is the fattest wire in both. (Labeled with a 4mm-diameter conductor on the diagram, the others are 2.5mm or less.) And that makes sense, as it's the power supply for the whole switch. After that, guessing gets hazardous.

OK, so you've checked each wire in each key position. The results don't seem to make a whole lot of sense, but this switch has a couple more wires than the one in the diagrams. (That's what happens when one book covers many model years, sad to say.) I would double-check those tests, as at least one wire should connect to 30 at all times but "off". If the tests give the same results, then I think the switch is the most likely culprit. It only makes sense that some things are powered with in "ACC", and others only when the key is in "run".

.... But as I said, I'm not very up on the BMW side of things ... Hopefully someone with direct experience can chime in here.

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A few pics of my car:
Old 09-03-2014, 01:56 PM
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