LS won't crank

[57FleetsideC4]

Hi All, I am to the point on my 57 pickup project that I am getting ready to start it. This is a LQ4 DBW with 4L80E trans. I can communicate with the pcm with my tech 2 no coded stored but won't crank. Trans data shows it is in park and have power at the purple wire going out of the switch. There is a start relay and if I cross the big red to purple it cranks. The green wire on the start relay has power and if I touch the yellow wire on the starter relay it then cranks. I also am getting the 2 second fuel pump prime signal. I am really not ready to start it yet but trying to get everything in order when it comes time. Thank You Steve

[bigmoe]

So no power to the start relay when the key is at Start position? You would have to work back from there. Do you have a neutral safety switch in that circuit?

[57FleetsideC4]

Originally Posted by bigmoe

So no power to the start relay when the key is at Start position? You would have to work back from there. Do you have a neutral safety switch in that circuit?

Thank You it does have a neutral safety switch but it is a many wire connector and don't know which pins are for that but the pcm is seeing the car in park so it might be ok. I am going to call the business that sold me the engine/trans/pcm/harness setup to see if they can help. It will probably be something simple. Steve

[D-n-Tyke]

These threads may help you if it is the neutral saftey switch on the 4L80 trans. They are from when I was researching how to wire up my NSS.

http://67-72chevytrucks.com/vboard/s...d.php?t=845747

https://ls1tech.com/forums/conversio...l#&gid=1&pid=4

[57FleetsideC4]

Originally Posted by D-n-Tyke

These threads may help you if it is the neutral saftey switch on the 4L80 trans. They are from when I was researching how to wire up my NSS.

http://67-72chevytrucks.com/vboard/s...d.php?t=845747

https://ls1tech.com/forums/conversio...l#&gid=1&pid=4

Thank You. I looked at the one with the starter relay and it looks like the dark green wire becomes hot when in park or neutral so I think that part is good. What feeds that yellow/black wire is where my problem must be. Steve

[D-n-Tyke]

Originally Posted by 57FleetsideC4

Thank You. I looked at the one with the starter relay and it looks like the dark green wire becomes hot when in park or neutral so I think that part is good. What feeds that yellow/black wire is where my problem must be. Steve

Are you using the factory fuse box out of the donor vehicle? Or are you using a standalone fuse/relay block as part of the modified LS harness? Similar to this (https://lt1swap.com/fuseblock_obd2port.html)