The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > General Truck Forums > Engine & Drivetrain > LSx Swaps

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 05-23-2018, 05:13 PM   #1
Jferrante
Senior Member
 
Jferrante's Avatar
 
Join Date: Jan 2015
Location: Princeton NJ
Posts: 358
Starter Wiring Help

I have a 6.0 with a PSI harness and am having trouble wiring this up correctly.
I have the main hot from the battery on the main post, the 2 black wires on the same post (per PSI instructions) then I have the Red wire that comes from the drivers side fuse block - this is where I am having an issue. If I put the red wire to the main post it doesn't turn over, if I put it on the small post of the starter I get it to run the starter but even when the key is off.

My troubleshooting is either the wiring at the relays is wrong or I am missing something altogether at the starter. I should only have starter full circuit with the key in the on position....
Any help is appreciated.
Jferrante is offline   Reply With Quote
Old 05-23-2018, 11:47 PM   #2
Wildkarde
Registered User
 
Join Date: Mar 2018
Location: Ardmore
Posts: 44
Re: Starter Wiring Help

I've never actually seen a PSI harness in person, but looking at the pictures in the instructions and reading them, the red wire coming out of the fuse block should go to a "ignition" source. The two black ones with the ring terminals go to either the large post on the starter or the battery "+" directly. On an ignition switch there are basically 3 different outputs. Accessory, which has power when the switch is in ACC and On, but not when cranking. Ignition, which has power when On, and when cranking. And Start which only has power in the cranking position.

You need to find a wire that has power when the key is on and while the engine is cranking. I like to use the one that powered the Ignition coil since it will already be in the engine compartment. Also, there is no actual cranking wire in that harness, you will need to either use the one that was already on the truck or run a new one yourself.
Wildkarde is offline   Reply With Quote
Old 05-24-2018, 11:27 AM   #3
davepl
Registered User
 
davepl's Avatar
 
Join Date: Aug 2006
Location: Redmond, WA
Posts: 5,925
Re: Starter Wiring Help

In my case starting the car was completely outside the scope of the LS harness.

There are two wires that go to your starter:

1) The big starter cable that runs to the battery post
2) The smaller purple wire that runs from the solenoid to ignition switch (and through the neutral safety)

You want the purple wire from the key to the solenoid. When you turn the key, the purple wire will go live and energize the solenoid. That in turn kicks the starter into action, drawing from that main starter cable.

Now it's up to your LS harness and computer to recognize that the engine is on and turning and to start firing the injectors and coils. For that it needs power and so on, which it gets directly from the battery. There is also an Ignition sense line (typically pink) that the ECM has that tells it when the ACC/IGN is ON.

What system is this?
__________________
1970 GMC Sierra Grande Custom Camper - Built, not Bought
1969 Pontiac 2+2 427/390 4-speed Coupe
1969 Pontiac 2+2 427/390 4-speed Convertible
davepl is offline   Reply With Quote
Old 05-24-2018, 11:35 AM   #4
truckdude239
Senior Member
 
truckdude239's Avatar
 
Join Date: Sep 2005
Location: Lewisville, Nc
Posts: 9,724
Re: Starter Wiring Help

The red goes to the big post and then u need to find the facotry signal wire from the igntion switch there is no signal wire in the ls harness
__________________
David fuller
Ase Certified Mechanic
Click here to help support our board!!


1971 Chevy c-10 under going a 4.8l LSx swap

Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305

2007 Honda Accord my daily 101kmiles
2002 Honda Accord 4 door With 275k(sisters car)
2003 Honda Accord 109k( brothers car)
2002 Sububran 5.3 225k
2000 Tahoe 5.3l 369k

General manager for Marco's Carwash & lube
truckdude239 is offline   Reply With Quote
Old 05-24-2018, 06:38 PM   #5
Jferrante
Senior Member
 
Jferrante's Avatar
 
Join Date: Jan 2015
Location: Princeton NJ
Posts: 358
Re: Starter Wiring Help

Thanks - the truck was running before I tore it down to the frame so I was working off what was there and I am missing something obviously. I just tested a direct line from the small post to the ignition switch and that gets it to turn but now I need to figure out where that wire needs to go on the other side of the relay to make it all work.
Jferrante is offline   Reply With Quote
Old 05-24-2018, 10:52 PM   #6
Wildkarde
Registered User
 
Join Date: Mar 2018
Location: Ardmore
Posts: 44
Re: Starter Wiring Help

is this the harness you have https://www.psiconversion.com/instru...structions.pdf

If so, what I said in my earlier post is correct. That small red wire energizes one of those realays, which then powers all stuff on the engine that needs switched 12V, coils, injectors, O2 heaters, ECM, TAC module and a few other things. The two large black wires that are down by the crank sensor go to the large battery post.

If you still have it, the coil/distributor wire works well for triggering the switched 12V relay.
Wildkarde is offline   Reply With Quote
Old 05-25-2018, 12:00 AM   #7
mongocanfly
Senior Member
 
Join Date: May 2015
Location: Alabama
Posts: 5,956
Re: Starter Wiring Help

I used a psi harness...the psi doesn't do the actual starter cranking ...you need to use original truck starter wiring that cranked your old engine....
__________________
Mongo...aka Greg

1981 c30 lq9 nv4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598
1955.1 ls3 tr6060...(under construction)(on hold)
2013 gmc z71. (daily driver)
Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563
mongocanfly is online now   Reply With Quote
Old 05-28-2018, 10:26 AM   #8
Jferrante
Senior Member
 
Jferrante's Avatar
 
Join Date: Jan 2015
Location: Princeton NJ
Posts: 358
Re: Starter Wiring Help

Quote:
Originally Posted by mongocanfly View Post
I used a psi harness...the psi doesn't do the actual starter cranking ...you need to use original truck starter wiring that cranked your old engine....
This is where I was missing - I ran a wire from the starter to the ignition on the truck harness and all is good now. Now i need to figure out why my fuel pump wire from the PSI harness isn't sending a signal in ACC mode.
Jferrante is offline   Reply With Quote
Old 05-28-2018, 10:33 AM   #9
mongocanfly
Senior Member
 
Join Date: May 2015
Location: Alabama
Posts: 5,956
Re: Starter Wiring Help

acc or switch on?
my pump doesn't run in acc.....only switch on...really no need for it in acc
__________________
Mongo...aka Greg

1981 c30 lq9 nv4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598
1955.1 ls3 tr6060...(under construction)(on hold)
2013 gmc z71. (daily driver)
Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563
mongocanfly is online now   Reply With Quote
Old 05-28-2018, 10:56 PM   #10
Wildkarde
Registered User
 
Join Date: Mar 2018
Location: Ardmore
Posts: 44
Re: Starter Wiring Help

The fuel pump should be controlled by the computer, will run for ~3s when you first turn the ignition on unless the computer detects the engine spinning.
Wildkarde is offline   Reply With Quote
Old 05-31-2018, 08:28 PM   #11
binford
Junior Member
 
Join Date: Aug 2004
Location: Sacramento Ca
Posts: 94
Re: Starter Wiring Help

Correct, when you turn the key to ON the fuel pump runs for a few seconds. When you turn the key to Start, the starter will spin and the PCM will be pulsing the fuel injectors. So the fuel pump is on, but you can't hear it over the engine.
binford is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 04:26 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Copyright 1997-2013 67-72chevytrucks.com