03 Cobra - No crank, cluster loses power while attempting

[SVT3571]

03 Cobra, factory ECU, 6R/USS Q6

Car cranked over and ran, once shut off it will no longer crank. Cluster and gauges will lose power minus 2 lights while in the crank position, and then they come back on when I release it.

- trunk battery relocation with remote solenoid, fuses good
- driver footwell starter fuse good
- engine bay fuses/relays for starter and ignition all good
- NSS relay (6R, USS Q6) is good

Not sure where else to look? Just randomly happened as it started perfectly fine just before this happened. The starter also doesn’t click or anything, it’s just silent when I turn to crank. TIA!

 

[hotcobra03]

Dirty terminals get me all the time,
Does just this.

I do have after market terminals,,under the clamps is where mine seam to get Dirty,

 

[SVT3571]

Airbag, battery and seatbelt are the only lights in cluster that stay on

Terminals are brand new as well, no painted ones just bare metal. Super clean

Disconnected scavenge pump and fuel pump fuse , I can hear solenoid clicking on turn of the key but no crank

 

[01yellercobra]

How old is the battery? How many times has it been run down?

 

[hotcobra03]

Pulling starter and bench test ?

Unless you can get to power wire at starter to test for ignition power when key is turned.

I've had starter issues ,,some work ok till hot,,and had 1 that passed bench test, but told them try it a few more,,and than it quit.

Another thread out on a guy with same issue. But battery in front,, no crank unless he adds another ground to motor

I also had that issue ,cause was main stud on engine mount where ground goes snapped. Never fell but caused starting and charging problem

Wiggle test and it came off

 

[SVT3571]

Pulling starter and bench test ?

Unless you can get to power wire at starter to test for ignition power when key is turned.

I've had starter issues ,,some work ok till hot,,and had 1 that passed bench test, but told them try it a few more,,and than it quit.

Another thread out on a guy with same issue. But battery in front,, no crank unless he adds another ground to motor

I also had that issue ,cause was main stud on engine mount where ground goes snapped. Never fell but caused starting and charging problem

Wiggle test and it came off

How old is the battery? How many times has it been run down?

Battery is a few years old, been on a tender when car isn’t driven

I’m going to try and jump the rear solenoid and see if it cranks it over, idk what else would cause the starter to all of a sudden fail (the car started up first try no issues 2-3 minutes before this happened - I shut the car off and then this started. Maybe the rear solenoid could be an issue? I followed this diagram (attached)

The cables for grounds are all brand new and clean, shouldn’t be an issue anywhere and I even ran a cable from the rear ground location to the front to join with the factory ground cables

I’ll update once I can verify the rear solenoid is working / not working. But I’m still stumped why the cluster boots up as usual in run but as soon as I turn to crank, it loses basically all power minus the 3 lights mentioned earlier

 

[SVT3571]

Quick update: realized the Q6 controller was showing me it was in 3rd gear, slid under the car and realized the transmission plug wasn’t fully locked into place and the vibration of the car running must have backed it out enough to cause the trans to go into limp mode - one forward gear only (3rd) - face palm. Pushed the plug back in and turned the key over to run, controller showing “P” and cranks as it should. I guess since it wasn’t fully inserted, it caused the car to not start as it was in gear. I probably could have unplugged the trans connector and it would have fired up but I didn’t bother trying.

Now I’ve realized though that the factory crossmember brackets welded to the tunnel are actually in the way of the plug being able to fully turn and lock in place - I never read anyone else have this issue but it’s definitely a problem so next time the trans is out I’ll remove those brackets. In the mean time, I have to find a way without dropping the trans to notch that bracket so the plug can lock in.

 

[Bullitt1448]

Great news! Glad you found the problem, and great info for anyone dropping the trans in the future, thank for your hard work and update!

 

[SVT3571]

Here’s a shot of what I meant for anyone who didn’t understand (if anyone)

The Q6 harness tab is too long and hits the bracket and physically won’t push into place, let alone lock into place. It turned *maybe* 20% of the way in prior to cutting the notch you see. I recommend before installing your 6R to remove that bracket entirely or just notch a big cutout like I did. Tool of choice was a die grinder and just ate away that big section as I didn’t want to remove anything or drop the trans.

Now seeing how far it actually turned to lock into place, I feel stupid that I thought it was okay previously. Live and learn!

 

[01yellercobra]

Is this something that should be added to the thread about running the 6R80?

 

[SVT3571]

Definitely could be. I think it’s important people know of this small issue prior to putting the trans in as it will save a lot of hassle. Personally I’m in my single car garage on the floor doing my work so no hoist or trans jack to make it easy to remove, better to know all the tricks before starting! Debating on making a full thread anyways, I documented a lot for the swap from the current couple threads and saved all the part numbers, parts required, etc that I was able to find on here and my own research for future reference, if it would help anyone else