Backfeeding the fusebox/cab???
12-07-2009, 08:51 AM
#1
Launching!
Thread Starter
iTrader: (7)
Join Date: Oct 2008
Location: Cocoa, FL
Posts: 202
Likes: 0
Received 0 Likes
on
0 Posts
Backfeeding the fusebox/cab??? Quick details:
2002 Silverado 5.3/4L60E into 1994 GMC 1500 ext cab long bed
self modified harness, using stock 5.3 2002 Silverado fusebox.
So here's the deal, I modified my harness using LT1swap.com instructions, but I wanted to see if anyone has had this issue. If I key on, everything works the way it should, power inside the cab, fuse box, fuel pump (kind of). However, if I key off without starting it, it kills the power inside the cab, but if I key on and START the truck, I have to remove the battery cable to kill the power to the engine and to the cab. It seems like it is backfeeding some how.
I have a wire going from the battery to the firewall (dist block for truck), a wire to the 2002 silverado fuse box, and what should be a KEY 12V going from the fuse box inside the cab to the 2002 silverado fuse box to power up the engine/trans fuse box. Somewhere in this whole mess, it seems I am backfeeding power to the cab, which in turn will not allow me to kill power to the KEY 12V that actually keeps the engine running. I would imagine it is the line going from the battery to the firewall, but it shouldnt be as I am using the wire that was originally running that way with the fusible link still in tact.
I guess it could be the 12ga wire running from the 94 fusebox to the 2002 fusebox, but it shouldnt be as it is nothing more than a trigger wire to show KEY ON 12V.
Has anyone had a backfeeding issue before, and if so, how did you fix it? My dad said he had a backfeeding issue on his race car years ago, but cant remember how he fixed it. Thanks Dad, lol.
2002 Silverado 5.3/4L60E into 1994 GMC 1500 ext cab long bed
self modified harness, using stock 5.3 2002 Silverado fusebox.
So here's the deal, I modified my harness using LT1swap.com instructions, but I wanted to see if anyone has had this issue. If I key on, everything works the way it should, power inside the cab, fuse box, fuel pump (kind of). However, if I key off without starting it, it kills the power inside the cab, but if I key on and START the truck, I have to remove the battery cable to kill the power to the engine and to the cab. It seems like it is backfeeding some how.
I have a wire going from the battery to the firewall (dist block for truck), a wire to the 2002 silverado fuse box, and what should be a KEY 12V going from the fuse box inside the cab to the 2002 silverado fuse box to power up the engine/trans fuse box. Somewhere in this whole mess, it seems I am backfeeding power to the cab, which in turn will not allow me to kill power to the KEY 12V that actually keeps the engine running. I would imagine it is the line going from the battery to the firewall, but it shouldnt be as I am using the wire that was originally running that way with the fusible link still in tact.
I guess it could be the 12ga wire running from the 94 fusebox to the 2002 fusebox, but it shouldnt be as it is nothing more than a trigger wire to show KEY ON 12V.
Has anyone had a backfeeding issue before, and if so, how did you fix it? My dad said he had a backfeeding issue on his race car years ago, but cant remember how he fixed it. Thanks Dad, lol.
12-07-2009, 11:34 AM
#3
What about the Alternator... how is that wired up ? seem that as long as the Alternator is still spinning and generating voltage, your still getting power to the PCM and the engine is running on. What is feeding the Alternator B termnial ?
I am no expert when it comes to eletrical. But I had a simular problem with my Nova when I swapped in a HEI dirtibutor.. I had problems of run on also.. I changed some of my power sources and that corrected the problem, why ?? got me but it works now... so I left that way.
I am no expert when it comes to eletrical. But I had a simular problem with my Nova when I swapped in a HEI dirtibutor.. I had problems of run on also.. I changed some of my power sources and that corrected the problem, why ?? got me but it works now... so I left that way.
12-07-2009, 12:06 PM
#4
Launching!
Thread Starter
iTrader: (7)
Join Date: Oct 2008
Location: Cocoa, FL
Posts: 202
Likes: 0
Received 0 Likes
on
0 Posts
The alternator B terminal? on the back of the alternator? I am using all the silverado wiring, including the battery cables, alternator wiring, etc. The harness, engine, ECU and battery are all wired just like it was in the silverado. I pulled all the stuff myself from the truck, so I know the silverado didnt have this issue. Im sure that it is something stupid simple, but gotta find it.
12-07-2009, 02:17 PM
#5
As a test.. I would isolate the IGN Power 12+volt that feeds the PCM.. make sure your not getting any voltage as you turn off the key (?). make sure only the PCM in on a seperate Key/IGN 12+v circuit... or try using a jumper for not to see if you remove the power the engine shuts down ? just grasping at suggestions..
12-07-2009, 02:34 PM
#6
Launching!
Thread Starter
iTrader: (7)
Join Date: Oct 2008
Location: Cocoa, FL
Posts: 202
Likes: 0
Received 0 Likes
on
0 Posts
the constant 12v or the key 12v? I will look over everything this week, as the motor is currently sitting behind the truck while I paint the frame and block.
