Sons 2007 Jeep Liberty Won't Start

[Daveh]

Ok here were my readings:

No running - 12.24
Running - 13.74

Thoughts????

[Chryco Psycho]

The alt is definatly working so the computer is doing that part although both readings are low side

[Daveh]

So do I take the alternator out and have it tested at Napa as a double check or could it be something else? If you think it's something else where do I look next?  Thanks

[Chryco Psycho]

Alt is working , normal battery voltage should be 13.2  with no load & running 13.8-14.2
but if you had the key on while not running when testing it could be reading 12v range , the fact that it exceeded battery voltage at 13.8 shows it is working fine.
you have tested / swapped relays so that is not the issue .
There are 4 terminals on the relay  , the 2 you shorted & the 2 to the left & right , likely 1 has constant power the other will ground through the computer , you need to test this , you could have switched power but unlikely , the ground circuit is the problem is my guess , you could run a pair of wires to a switch inside the vehicle , flip the switch & it would activate the start relay & over ride the computer that is not closing that circuit when you turn the key .

[1 Wild R/T]

Need a schematic to determine what triggers the relay.... I doubt the PCM commands the relay that powers the PCM.....   Now if it were the fuel pump relay then yeah the PCM commands the fuel pump on but the first relay controls the power to the PCM & I believe that is powered off the ignition switch......

Just knowing you can jump the relay & it'll run puts you well on your way, allot of stuff has been proven good...