Well, I'll start with what is happening and then tell the story.

Key on works normally. My fans are constant on. Everything works. I turn the key to start, a loud click possibly from the ECM and then all power is lost. Everything dies. Power will not come back unless I disconnect the negative battery terminal to reset the ECM. Then, power comes back and everything is normal... until I try to start the car. Same thing, it never misses. If I disconnect the trigger wire on the starter, the issues disappears. The car doesn't start, but it doesn't kill power.
All fuses good.
No codes what so ever.

Previous issues

For about a month now I have been getting hesitating starts. The solenoid clicks, but it takes a split second for it to push all the way out for the motor to start. Once the starter motor engauges, it starts easy and strong. When the engine is hot, it won't start at all. When hot, the starter works perfectly if jumped straight to the battery. So, this told me that it was either a bad solenoid or a bad trigger wire.

I check the wire, it was burnt up. I replaced the last foot of it with the proper primary wire and soldered/heat shrunk correctly (believe me, it's done correctly. Soldering is my job). That is when the issue above started. 2 days ago.

The starter that was on the car before is only about a year old, but it was sitting next to long tube headers, so I suspected a shorted solenoid. I have put 2 different starters, both from NAPA (who I trust). Same issue. WHAT COULD CAUSE THIS?

Again, power is good during key on. ALL electrical power lost when key is turned to start after a loud click from engine bay (possibley from ECM). Power can only be returned after the battery has been disconnected and ECM resets.

It seems like the ECM senses an over-voltage and kills the system to protect it.

Possible causes that I have so far.

Bad solenoid - I highly doubt that 3 of them are bad, so this is not likely at all.
Bad battery - Interstate battery, only a year old. I doubt it.
ECM pissed of? - possible


Any ideas? Please help. I am completely out of ideas. I have spent 8 hours a day for the last 3 days straight and I am completely out of ideas.

 

This sounds very similar to the symptoms I had when my battery leaked acid at the positive terminal and the acid ate up the copper wire inside the battery cable. Even a jump from another car would not start the engine.

I suggest disconnecting and cleaning both battery cables (BOTH ends).

 

Cliff,

Did the ECM drop power when this happened? I've been getting other replies involving the batter cable, so it is something I will try.
Correct me if I am wrong, but doesn't the primary + battery cable go straight to the starter? If so, I can get a new one in pretty easily. It'll take some work, but I can get it done.

I do not have an FSM anymore, and I have been searching the internet without much luck. Does anyone have an electrical diagram of the start signal path? I know it goes thru the firewall thru one of the harness connectors from the start allow relay that is under the driver's side dash. However, I need to know the pinout for all of the firewall harness connectors. I'm going to completely replace the start wire instead of patching it up.

 

When you say all power is lost after turning the key to start like all warning lights around the dash, DIC, as well as the instrument lights?

The CCM plays a big part in lightening many lamps as well as a few other individual modules.

The ECM is not really a lamp lighter. It really takes sensor inputs and controls the engine.

Do your chimes (ding ding) work?

With the fans running it's a symptom of limp home mode. The ECM can do that or something can be wrong causing the ECM to go into limp home mode.

Consider you might have more than one problem.

Check the 2 boxes of fuse links (under the hood) to see if anything is burnt.

Another thought also came to mind was if the ignition switch could be a problem.

 

When my battery cable was bad the lights would all come on (the dash lit up) when I turned on the ignition. When I put it in the start position all the lights went out and nothing happened. The voltage was being dropped to near zero across the bad connection inside the battery cable.

 

I have seen this on many cars and it always was a poor battery connection. Usually the positive connection.

 

I have seen this too. Check alllll the terminals both ends. Do the simple and basics first before going in left field.

 

Bad connection, Somewhere. Could be loose or corroded. Jump the Vatts and turn the headlights on and crank the motor. If the lights go dead. Low or dead battery and or loose connection, somewhere. Disconnecting the starter only tells ya that your nixing a pretty good draw on the system. Like when your battery barley has any power and you try and start your car and it just clicks.

What yr you have? They also have a junction block you need to check.



Here is an older C4 showing how to jump the vatts and why

 

I found out what the issue was. I wired a 10 gauge jumper from pin-30 (primary power) on the starter allow relay to the start pin on the starter itself. She started up with zero issue. No delay, no jump. Just a good start. That means that the purple original start wire is bad. It has probably gotten too hot and damaged. Heating the wire to solder the last section on was probably the last straw. This wire goes from one of the bulkhead connectors on the firewall straight down to the starter. The problem is that I don't know where it is. I don't want to start rummaging around.

I need to know what connector and hopefully pin number that wire is on. It's an 10 gauge purple wire going from the outside bulkhead connector straight to the starter. I'm going to replace the entire thing and re-pin it. Does anyone know where it is?

As for the relay that Cudamax showed, in the later models that relay is under the driver's side dash. I bypassed the relay and had the same issue. That is also the same relay that I jumped straight to the starter. That is how I know it's that purple wire. It could be the yellow wire in the cabin, but I doubt it. It's in a controlled environment.

 

Let me reiterate and understand that you want to replace the purple wire to the solenoid.
My 94 book says that it goes to connector C100C pin 6. I think that’s right but I'll see if I can get a look at the car tomorrow.

 

That is exactly what I need. Thank you very much.

 

You've never mentioned the year of your car and if you'd like to start tampering with the C100 connector it's going to be to your advantage to mention THE YEAR OF THE CAR.

 

I thought it was a 92 but looking at the profile now it is a 91. Thought it was a LT1. My information may not be exactly right so take it with a grain of salt.