99 Yukon no crank -- Moved from incorrect sub-forum

[A2theR84]

Recently replaced engine in friends yukon, 5.7, and it will not crank with the key, however if i jump the starter from the starter relay under the hood with the key turned over it fires right up
any help would be greatly appreciated

 

[SunlitComet]

Sorry I over looked your post earlier. Neutral safety circuit perhaps. Or maybe factory security system if installed

 

[gpracer1]

Check all the basic stuff like fuses, wiring to the starter and solenoid, neutral safety and gear select area on trans, and any pinched wiring between engine and trans.

 

[A2theR84]

checked everything that i thought would make sense
i was checking to make sure all fuses in the cab were good, and when i checked #14 illumination with the key turned on, the truck started right up, wtf,this is without turning the key over, just in the on position, also with the key between locked and on, the shift indicator works, but when i put it in the run on position the light shuts off
again all help is very much appreciated

 

[SunlitComet]

illumination is correct to key position but if the truck started with out moving to start something is amiss in the key switch. or you have a short under the power box or in harness.

 

[A2theR84]

thx for the reply, do you know if this is a symptom of the ignition switch?
also if i pull the illumination fuse the security light stays on solid

 

[SunlitComet]

Unless I forgot the security should shut down fuel pump no starting circuit so if it cranks on own continuous or no crank at all. the then problem is in the starter circuit. Use the diagram below and probe for problems.

And print this out first.

Starting And Charging Schematics (Starter Controls)