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1990 525i RPM sensor

Greetings and salutations, I have some questions about my 525i. First a little background: My 525i stopped running last week. I have the Bently Service Manual and have been going through troubleshooting a no-start condition. Ignition components appear alright, however there is no spark. The manual instructed checking the resistance of the Crankshaft/RPM sensor. The ilustration in the manual shows that wires 1 & 2 go through a coil and should have 540 ± 10% ? resistance. Connector 3 shows that it is grounding a shield surrounding wires 1 & 2. There is an open circuit between the number 3 connector and the metal body of the sensor. My questions are: Should there be continuity between the number 3 connector and the sensor body? Could this cause the no start condition? What else is a common cause of a no-start condition?

Thanks in advance, Homer

Reply to
Homer
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It wouldn't surprise me if it were only grounded at the ECU end - two grounds can cause loops and add to the interference rather than help stop it.

Reply to
Dave Plowman (News)

When my 89 325i stopped running, this was the culprit. One of the wires had broken right at the sensor and was making intermittent contact. Real pain in the ass before I happened on the actual problem...

Reply to
Psycho

Thank you all for your kind replies.

Another fact that I failed to include in my OP is that the code reader (scantool) I bought from an Internet site displayed an "E" when I ran the diagnostic command to retrieve any trouble codes that may have been stored in the car's computer. A normal display has always been "--" in the past when no codes were found. The "E" code was not listed in either the Bently manual nor the scantool user's manual. A call to the vendor of the scantool failed to define the "E" code.

Dave Plowman advised that the isolated shielding in the disconnected RPM sensor could be normal. The only other sensor displayed in the circuit diagram was the #6 Cyl sensor. I had recently replaced the sparking plug wires (they included a new sensor) so I assumed that it was not a part of the no-start problem.

The Bently manual suggested (in the maintenance section) that owners of

1989 -1995 5 Series BMWs should always carry a spare DMI main relay. I purchased one from the local dealer for $21 UDS and installed it in the underhood electrical box. The engine started thereafter and there has been running really well since. The car keeps burning out other seemingly unrelated fuses such as the power mirrors and A/C, so I know that there are other issues yet to resolve, but at this point I can drive to work to earn money towards additional repairs.

Thaks again, Homer

Reply to
Homer

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