electrical and ignition M10 signal to starter (fried crane xr700 ignition?)

[Jesse Burgman]

Hey guys, I'm having troubleshooting what happened to my ignition. Up until last night the car started perfectly, however while performing some maintenance, (plugs, wires, fuel filter) I knocked the ignition signal wire off the starter.

 

When I hooked the wire back up, I didn't realize there was more than one spade on the starter solenoid and I accidentally plugged it into the ground. When I turned the key and got no response, I investigated further and found the correct connecter (+) and hooked it back up to that. While diagnosing I also jumped the starter to the battery to make sure it was correctly functioning.  

 

However, now when I turn the key I get dash lights but no response from the starter. I've checked continuity from the starter to the balast-resistor, and from that to the coil and ignition unit with positive results. I've also checked the ignition grounds, and they look okay also. The only other clues I have to this mystery is that the ignition unit has a LED that's normally on when the car is running, but it won't light up now, and if I leave the ignition on the red wire between the ignition unit and the balast-resistor gets hot, as does the balast resistor.

 

 

[Tommy]

Well I can't say what is wrong but I can tell that if your starter doesn't run it doesn't have anything to do with ignition system. It must be something in ignition switch or wiring, assuming the starter was running when jumped. If your starter is running but the engine doesn't start you might have fried the XR700 while diagnosing. Also what comes to my mind is that I don't think there is ground spade around starter, there is the spade straight to positive and the start spade to solenoid...?

 

  hth, Tommy

[Jesse Burgman]

Thanks Tommy, my starter looks this.

 

Cliffs notes for the steps I've taken below... 

• Car started fine and I pulled into the garage. While working on it, I accidentally knocked the signal wire off the spade connecter of the starter and the car wouldn't turn over.
• I put that wire on the TOP spade connecter accidentally. Tried to start and the car wouldn't turn over. Maybe I toasted something here? 
• Disconnected the signal wire and jumped the starter. Starter turned over
• Connected the signal wire to the BOTTOM spade connector and ran continuity tests which all looked good. This appears correct based on other threads I've seen. 
• Two lingering concerns are 1) LED on ignition box doesn't light up any more, 2) Balast resistor and red wire from ignition box to balast resistor both get hot.  

 

[Tommy]

The question is does it turn over now?

 

If not then you are missing the wake-up signal from the ignition switch to starter.

If yes you're missing voltage from the XR700 - or it's fried.

 

Maybe you knocked out another wire...or burnt a fuse...

 

  Tommy

[Tommy]

I put that wire on the TOP spade connecter accidentally. Tried to start and the car wouldn't turn over. Maybe I toasted something here? Disconnected the signal wire and jumped the starter. Starter turned over

 

These things you did should not cause any damage. The top connection is actually what bypasses the ballast resistor during start. If I read the diagram right it's not connected anywhere except when solenoid is pulling. Also if the signal wire was disconnected when you tried jumping it shouldn't cause any damage but maybe you caused some voltage spikes or shorted something at some point...hard to say. 

 

  Tommy

[Jesse Burgman]

Ahh ok, starter doesn't turn over. I misunderstood how the the module interacted with the rest of the system when I was tracing wires. I did a little more poking around with the my multimeter (analog).

 

Known status:

1. Ignition switch has @12v on crank

2. Resistance across outside terminals of coil is around 3ohms

3. No reading for resistance from outside terminals to HT terminal at center of coil (odd? no continuity?)

4. Grounding the black lead of the multimeter at battery, I only pickup voltage at one side of the ballast resistor (@9-10v), and none at the coil with the ignition in the on position.

5. Following the same method, I see no voltage at the coil where the starter signal wire is hooked up, and the ignition is in the crank position. 

Edited July 7, 2015 by vdubious

[Dev02]

If you have no cranking I would suspect power to the starter itself. Ignition might keep it from firing, but should not effect whether the starter turns over. Have you checked power going to your starter? That the lead is delivering power, and that the ground is, well, grounded? If there IS power, and it is grounded, then I'd suspect either your starter is bad, or somehow stuck, like maybe it engaged the ring wrong and has not disengaged (I had it happen on another car).

 

Just my thoughts based on your descriptions.

[Jesse Burgman]

The starter is in working order for sure. The issue appears to be that the signal wire isn't energizing the solenoid. I have 12v at the ignition switch, so tracing wires back from the switch and the starter put the problem somewhere in the vicinity of the coil or ballast resistor. The ignition module is also in that area and not powering up either, which initially led me to think it was the culprit.

[Tommy]

Alright - at this point you can forget ignition system (xr700, coil and ballast). First you need to find out why it's not even cranking. Here you can find one circuit diagram. I'm not sure if it's matching your car,..or the best possible quality.

http://www.bmw2002faq.com/topic/103842-turn-signals/

 

Try to follow where you loose the voltage that should activate the solenoid. It's the line 60, (? I think, not the greatest image quality) coming from the ignition switch.

 

  Tommy

Edited July 7, 2015 by Tommy

[Jesse Burgman]

Got it, so following the diagrams and some other threads it looks like I've been tracing the wrong wires. The wire from the starter I've been referencing splices at the ballast resistor and terminates at the coil. I've read about a bypass circuit for getting full voltage to the coil under cranking.

Following Tommy's diagram I should have a straight uninterrupted run from terminal 50 on the ignition switch to the solenoid. However, I'm not seeing any additional small gauge wires near the starter beyond the one to the coil. Any ideas? It's been running like this for as long as I've had it.

[Jesse Burgman]

Great news...We're back in action! d'oh. Found the missing wire connector had slipped completely back into the convoluted tubing loom under the car. Not the most dramatic conclusion, but I'm happy she's back on the road.

[Jesse Burgman]

Almost forgot...Thank you Tommy and team.