Diagnosing starting issue

[SnowyOwl]

Will the car start and run if you turn the key on, and jump the starter solenoid to the 12v terminal? If so, it's something in that wire that starts at the ignition, goes thru the mlps, to the starter. You'll have to trace it out. I had a crap anti-theft alarm in the tbird when I got it, and it caused all kind of problems. If they cut the wire in question and added a relay, like mine, that would be your problem. find the relay, and fix the wiring back to factory. Or put a pushbutton rated for at least 5 amps in a wire directly from battery + to the solenoid, and use that to start the car.

Yeah it starts fine with a direct jumper cable from the battery positive to the starter solenoid. It just seems a pain-in-the-arse job to trace it all in between, but seems no other way around it.

 

[1997ThunderbirdLXV6]

The black wire looks stock to me. Those aftermarket alarms are usually all under the dash I would think.

 

[1997ThunderbirdLXV6]

Someone correct me if I'm wrong, but isn't the brown box in the trunk the steering control module?

 

[massacre]

Agreed. Check the wire colors against the manual for each pin. Example: R/LB = red/light blue, etc.



With this in mind, I think you'll have to examine the entire path of the wiring. In 97, that would be the path shown below; 94 may vary.

View attachment 12433View attachment 12434

My car is opposite as this as far as wire color-
ignition switch to MLPS is W/PK
MLPS to starter solenoid is R/LB.
Instead of testing voltage, test continuity to follow the circuit path through the various components.

 

[SnowyOwl]

Not much to update on this issue. I got myself a set of backprobe pins to narrow down where the problematic connection is, but before I got into using them the problem disappeared, and the car starts normally from the key again Need to wait until it re-appears again.

I've located the aftermarket immobilizer main unit, it was under the dash (as someone here expected). When the starting issue re-appears I'll begin by ripping that thing off.

 

[Jae 'Bird]

I've located the aftermarket immobilizer main unit, it was under the dash (as someone here expected). When the starting issue re-appears I'll begin by ripping that thing off.

SnowyOwl looking at the aftermarket immobilizer just waiting for the next time the car doesn't start