hi all,
i'm sorting through all the electrical problems in my car using the power probe short finder to detect shorts. one problem is the engine cuts out and a clicking sound happens when i start. i detected a short from fuses 11, 12, and 13, all leading past the ignition coil and ending in starter motor somewhere (not sure if it is in harness very near motor or motor itself) without the key in ignition. does that mean i need a new ignition (as well as starter motor or harness) since i don't think i should be able to detect that without the key in the ignition.
thanks all,
jigen3

 

are the connections dirty at the solenoid???....how about the wires under the harmonic balancer...mine were almost cut through as the were rubbing on the balancer...

 

the ignition coil and the starter motor aren't even connected. the powered side of those 3 fuses is tied together, and to the ignition switch pin 15 such that they are powered in positions II (run) and III (start). the load side of those fuses goes t...

11: heated rear window, automatic overdrive
12: reverse lights, power windows, a/c control
13: hazard lights, fasten seat belt reminder, seat heaters

now, ignition switch pin 15 also goes to the battery charge light, and from the to the D+ terminal on the alternator, and provides the 'bootstrap' current for the alternator to turn on.

the Chrysler ignition system used on 87/88's also gets its power from the ignition switch pin 15, same as those fuses, but it does not go through the fuses. This switched power goes to the coil pin 15 and on to the Rex ICU thats inside the front right fender. be very careful with the connector plug into the ICU, don't disconnect it if you don't absolutely have to, and if you do have to unplug it, pull it straight out.


the starter solenoid gets its power from ignition switch pin 50 (III only),and the starter motor itself gets its power from the really really fat red wire from the battery.

 

thanks for the answers. i undid the straps that hold all the harnesses together so i could better follow where it went from the ignition coil and followed it to the ICU, not the starter motor like i originally thought. i had to open up the harness underneath the car since it was giving me weird readings and thought a short might be in the harness, but there wasn't one even tho the covering was rigid brittle and wires inside were all oily.
so i dunno if anyone used a short finder before, but is detecting a short in the ICU (or other component) without a key in the ignition mean the component has gone bad?
@pierce, why should i not disconnect the ICU? is it easy to damage the connectors?

 

It depends on the circuit. I have no idea what this 'short finder' is, I've always used a ohm meter (the ohms setting of a digital volt meter).

that 87/88 ignition harness is unobtanium, if yours fails, you'll need to build a custom harness, recycling the existing connector shells (you CAN get the pin sleeves for the connectors). I would strongly consider NOT routing it under the engine if I had to build a new one

 

i guess a short finder works the same as an ohmmeter would by detecting a very low amount of resistance, except it would allow you to follow along wires better by tracking electromagnetic radiation given by wires and not necessarily having to open the harness sometimes.
anyway, i guess i'll go to the junkyard and pull an ignition control unit for testing. that part is kind of expensive new:\

 

the 1987/88 240's have a unique ICU, only used by those years. this ICU has a vacuum bellows on the bottom, which is used to control the advance electronically.. the plug on these is rather fragile, pull it /straight/ out without wiggling it, or the connectors won't make good contact.

fwiw, 87 was the first year for the big 'tv screen' headlights, so if the car has the older style rectangulars or rounds, don't even bother looking. 89+ 240's use LH2.4 injection, and a different Bosch ICU

 

wait. If you're basing this diagnosis on that 'short finder', I don't think this is a valid assumption. that short finder's test would only be valid if you disconnected both ends of a given harness so the circuit is open, otherwise every 'hot' in the car will appear connected when the corresponding circuit is switched on.