engine and drivetrain So the brand new ignition switch worked great... until...

[Lilleyvanilli]

Wouldn't start AGAIN this morn. New BMW ign. switch installed 2 days ago and doing fine. Did I get another bad switch? I have trouble shot the problem back to the switch after cleaning every ground that I can find, installing a new coil (but kinda knew it was OK). Fuel is ruled out. This is def. electrical and ongoing for 2 years. Runs great at all speeds, but then... just won't start. The symptom will present itself every 4 months or so. But here's the weird thing that keeps leading me back to the switch...

When this happens and I try cranking, when I start to turn the key back counter-clockwise to turn off, the car will sputter (YES, like it's trying to start!). Sometimes, I'll let it sit, or keep wiggling the key hoping to hit the 'sweet spot and I get lucky. Other times I'm calling a friend to get me. SO, I replace the switch, but the NEW switch just did the same thing! Didn't start all morning. After lunch I tried it again, and she jumps to life with barely one engine rotation! I swear I think I've got another bad NEW switch from BMW. Any thoughts?

[tinkwithanr]

Maybe try the signal wire going to the starter? or bypass the ignition switch with a simple push button and see if that helps at all?

[Guest Anonymous]

Did you change just the electrical part? Your symptoms make it appear it's in the mechanical portion of the key/lock assembly where it can't find the start/run position. You should have +12v to your coil in both positions and +12v to your starter just in the start position. Also if you have the resistor bypass circuit to your coil the wiring or relay may be acting up.

[Lilleyvanilli]

Yes, I changed just the elec. portion. And I'm curious... should I have coated the whole metal area with grease? My old unit had some grease on the little springloaded 'ball bearing' (I dabbed some there yesterday because the key felt like it was sticking/jambing a bit upon turning to start. Backing off and turning again would stop the binding feeling). So if my key assembly can't find 'start', how do I fix? What do I look for in the barrel area where switch mounts? Am I smelling an expensive die cast German purchase?

When you mention +12v in both positions, that's 'Start' and ? Also where/how to measure this with my meter?

As far as Resistor bypass circuit, would like to know where/how to check also. I have the equivalent to a Bosch Blue (no external ballast), but it is a 3 wire off the coil (brand new, BTW)

[Lilleyvanilli]

Possibly, but it will turn over all day long, so I think starter circuit is fine. Funny, you just reminded me of my first car... 1963 1/2 Ford Galaxie 500... with 'custom push button start'. Worked great for years.

[Mike Self]

position, the starter motor turns over but the engine doesn't fire. If that's the case, the problem is in the circuit that connects the "hot all the time" lead on the back of your ign switch to the "hot only when the key is turned to ign" (the "run" position) lead.

If that's the case, try this: identify these two wires. Make sure the "hot all the time" wire is actually hot all the time. Next time the situation occurs, run a jumper wire between the two wires, effectively bypassing the ign switch. If the car then starts and runs, there's a problem with the switch.

Now to determine if it's the electrical portion of the switch or the lock mechanism that's causing the problem:

1. disconnect the battery so you don't accidentally touch some live wires together, and remove the electrical switch from the key switch so that it dangles loose under the dash.

2. reconnect the battery, and then using a screwdriver or other suitable tool, try starting the car. If the electrical portion now functions properly with no jumper wire (as in the previous test), then there's some wear in the mechanical lock mechanism that isn't allowing the electrical switch to function properly. If you have to reinstall the jumper wire to make it work, then you have a bad electrical switch.

Finally--if everything above checks out, then the problem is in the wiring between the ign switch and the coil.

Good luck, and let us know what you found to improve all our knowledge; that's what the board is for!

cheers

mike

[Lilleyvanilli]

Thanks, Mike,

I have not done this yet, trying to find time, but when I do, you bet, I will post my findings for all.

Funny, but I've gotten REALLY good at starting the car... Turn key and crank engine over a few times (just to make sure it won't start), then release fingers from key and juice the throttle and "Brrrrooooom"! starts right up. Works every time. Now that I've said that...

[jgerry2002]

What year is the car? If its a '74 you need to swap out that extra starter interlock relay next to the ignition switch.

Just had to replace mine again due to a no start condition. You turn the key and you get nothing... wait about 5 minutes and the car will start up just fine.

[Lilleyvanilli]

My car is a '76. But it does sound like this is a similar problem. I wonder if my car has the same item beside the switch that you mention. Was this an expensive part or hard to install?

[Lilleyvanilli]

Just curious, does your '76 have this interlock switch or just your '74? I've looked at my '76 and do not see anything resembling what you speak of. Part # ?