I recently did a motor/transmission swap. I took the 3.7 motor and standard transmission out of a 2014 salvage title with 55k miles and put it into a 2010 with a clean title. I swapped EVERYTHING. The pcm, the battery junction box, ignition, radiator, cooling fans, wiring harness, everything! NOTE, the car ran perfect before tearing it apart and swapping everything. However. Now that everything is reunited in the 2010 car, 1) the car won’t crank by key, we tried running a wire from the hot wire in the ignition to the relay for the starter motor. It worked 3 times cranking by key then stopped. Now, 2) the motor will only crank by jumping the starter relay with needle nose pliers, and the car will crank then immediately die. Will not stay running, and the radiator fans come on immediately everytime the key is turn to the on position. Whether it sat there all night good and cold, or we sat there for 30 minutes trying to crank it. PLEASE HELP.

 

Welcome,


All it Takes Is One Wire To Muck Up The Whole Deal. Really I mean EVERY WIRE Harness Likely Needs To Be Swapped. Dash, Body Etc. We Just Went Through This With an 06 to 07 on Just One Wire Harness Which Caused Major Havoc. Same Thing as Well a While Back With One Wrong Dash Harness. The Instrument Cluster & All Modules Have To Communicate Properly. It is a Real Pain.

A Look At The Shop Manual Section & Module Functions Might Be a Good Place To Do Some Research. I Wish I Could tell You This Was a Simple Thing To Fix But Everything Can Plug Right in But The Pins Can Be in Different Locations One Year or Model To The Next.

At Least You Have The Whole Car Still?? And Can Reference Things Vs Just a Motor & Goodies Pulled From a Bone Yard. The 2010 is Kind of a Step Child With Elements of Both The Prior 05-09 and The Later 2011-2014 It is Kind of Unique.

Post 6 Shows All The Modules.

https://themustangsource.com/forums/...e-info-550475/

KC

 

Now when my friend did his V8 swap from the 2010 4.0 to the 2010 4.6 he changed out every harness, the ECU and the SJB. I think think the only ones that stayed were the doors and the taillights.
They were the same year so no telling with the switch in years.

 

Yeah, the switch in years would terrify me for sure. I've never been good with electrical problems in cars to begin with though, wiring scrambles my brains wiring lol.

 

Needs To Be Treated Like a Body Swap Not an Engine Swap!

KC

 

I think it has to do with all that wiring and stuff inside the dashboard that probably was not swapped out .... I know that stuff is integrated in many ways that might surprise you, and it is different across the years ... but way beyond my depth to get any more specific than that