Loading ...Q I have a 88 635csi. Last summer, I had an intermittent problem of no start when turning the key to position III. Sometimes it would start as normal. By last October the intermittent problem became permanent. The battery and all other electrical functions are fine. It is an automatic transmission car. I replaced the ignition switch but that fixed nothing. I know there is a start relay that links to the indicator switch on the transmission lever, but I do not know how to test. What is the most likely cause ….and how do I go about verifying cause? I cannot afford to keep replacing parts blindly!
A The following procedure would be applicable to all older model BMWs (through 1994) with automatic transmissions.
From your description, I assume your no-start is due to the starter not cranking when you turn the key.
In this case, with an automatic transmission, we have the ignition switch, shifter neutral-safety switch, starter relay and the starter itself (as well as the wiring).
First, let’s test to see if the starter is OK. Perform all tests with the shifter in the PARK position.
* Since you have already replaced the ignition switch, we will bypass testing this.
* Use a length of wire to jumper 12-volts (from the positive battery terminal) to pin #11 in the diagnostic connector plug. Alternately, you can run the positive jumper wire directly to the terminal on the starter solenoid. The terminal should have a small gauge black/yellow wire connected to it.
* If the starter cranks when the jumper is run (either to the diagnostic plug or the solenoid terminal), the starter is OK.
* If the starter tested as OK, access the starter relay. On the E24 chassis (6-series through 89), the relay is mounted under the driver-side dash. Remove the lower dash panel. The relay is to the left near the side kick-panel. It is mounted above a harness connector block, in the area forward of the hood cable lever.
* Pull the relay and socket from the top of the connector block (it will slide off the block). Note the wires entering the back-side of the socket (there should be four wires/terminals). Locate terminal #85, with the brown/black wire. Connect a jumper from this contact terminal to ground. Connect the jumper to the underside of the spade terminal where the original wire connects to it …. keeping the relay plugged in.
* Try the ignition key …. to crank the starter. If it does crank, you likely need a new shifter neutral safety switch. If it does not crank, you likely need a new relay.
Click here to see BMW Starters:
http://www.bavauto.com/se1.asp?dept_id=36
Click here to see your 635csi Neutral Safety Switch:
http://www.bavauto.com/shop.asp?HC1=0&Htarget=search.asp&HCY=1988&HCM=635CSi&SearchStr=neutral%20safety
Click here to see the Starter Relay for most BMWs through 1994 (with automatic transmission):
http://www.bavauto.com/shop.asp?HC1=0&Htarget=search.asp&HCY=1988&HCM=635CSi&SearchStr=0+332+019+456
