Diagnosis: Ignition Switch?

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x_atlas0

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Hey, guys.

During the Thanksgiving break, I got a chance to fire up the coupe. It has been in storage for the last 2 years or so while I have been at Texas A&M wrapping up my MSME. My Dad moved it last and unfortunately broke the throttle cable in the process. Thankfully, he put in some fuel stabilizer and I changed most of the fluids before putting it in, so it actually fired up on the first try with a charged battery.
Unfortunately, a problem arose shortly thereafter. It seems the car will start, idle for a short time, then sputter and die. It is not a fuel issue based on the smell and sound. The tach seems to fluctuate wildly before the engine cuts out, which would suggest some sort of ignition problem. It has a relatively new coil, and the wires appear fine. The ignition switch has always been a little dodgy, requiring me to rev the engine before letting go of the key when I crank the car.
Based on these symptoms, I'd like some opinions on what other possibilities could cause these problems. I'm running Motronic 1.3 by the way, not carbs or D-Jet. I have not had a chance to pull codes. Given the symptoms and performance, I think I have a dying ignition switch. What do you guys think?
 
Try the substation test routes...

If it is the lead from the ignition, try jumping it along the run with a separate lead ( undoing the lead that is there from both end points to confirm it is not the lead but before (at the switch).
Conversely bypass the RUN/On (bus 15) lead(at the switch) and connect to a HOT (bus 30) lead and see if it stays running.

Also, try swapping out the coil with another one, the spiking...

Check the Ballast resistors, if they are present in the M 1.3 circuit; you may have a failing run side Ballast if present. Is there a TEMP sensor in the 1.3, if so check resistance at the spec'd temperatures.

Finally, check grounds in the ig circuit, bad/corroded contacts can cause intermittent issues.

My thoughts for now...
Jon
 
Always start your no-run repairs witth a certainty of no fuel or no fire..

Carry a sparkplug with you always...

If you indeed have no spark>>>



You really need to ohm out the red to green leads to the ignition switch. Disco the switch and measure for resistance when the switch is in the # 2 position [run] You should see almost no resistance. Resistance of more than a few hundreds of an ohm will result in a poor running condition.
Jon's suggestion of a "home run wire" is right on the target. Simply place a fresh wire from battery to the Green wire at the switch connection. [with the switch disconnected]
Next- measure for battery voltage at the main relay [pins 30 and both pin 87's] when cranking. With 2 pieces of wire you can jump all three connectors for another Home run connection

Remember that Motronic 1.3 does NOT use battery voltage to activate the coil, the injectors or the relays- 1.3 uses grounds to operate everything. Including the green wire at the main relay.
 
Thanks for the ideas so far, guys. I will try to test this over the Christmas break.

I should have been more descriptive when discussing the tach. The car would be idling fine for a variable amount of time after starting, then the tach would randomly go to zero, then come back for a short time, only to drop to zero again. The engine started to die at that point, even with direct throttle input.

The fact that the tach read zero while the engine was running suggests, to me, that the coil was not firing, as the coil drives the tach. The coil can clearly work, as the car would idle fine for a short period. To me, this suggests the coil was being intermittently kept from firing. The only two things I know of that do that are the DME and the ignition switch. Since the car idled well for a short time and drove well in the past, that leaves the (known to be iffy) ignition switch.
 
main power relay

If you have a main power relay, try replacing it to see if that is the problem, most motronic systems use this and when the relay contacts get dirty or corroded they will act this way. I had a similar problem on a 735 and the car would just die sometimes in just a few minutes and sometime after 30 minutes, drove me crazy for a little while but was a quick and easy fix. Good luck, Leroy
 
A known issue with that harness is shorting from brown/orange to black...

Test for battery voltage at all THREE coil terminals with the key in # 2 position.
Less than battery voltage at the black wire terminal is indicative of a shorted positive to negative with no fuse... evil indeed.
 
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