need help getting my LS swap running

[cr92]

hey all, I've got a 1987 chevy r10 truck i recently put a 4.8/4l60e in.

motors in, i took all the wiring from the donor truck (2000 silverado) and put it in my 87. i then chopped off the engine harness for the 4.3 TBI that was originally in it and plugged that back in the firewall with a foot of slack for joining wires together.

anyway i found online that i needed the red wire, pink wire, and grey wire from the 87 harness to connect to the same colors on the 4.8 vortec fusebox harness. i connected them, along with the starter wire(purple) wedged under the fuse box against the 4.8 purple wire. when i turn the key the engine cranks over but won't start. i checked the fuel pump relay and i can't see any power on any terminal?

i manually bypassed that by running 12v to fuel pump and tried starting the truck like that but still nothing.

i guess the easiest way to describe what i have is the original 4.3tbi harness is cut off 1 foot from firewall plug in, the fuse box, computer and engine wire harness from 4.8 are all connected and untouched. then i have the wiring block c2 cut off the 4.8 truck and bolted to bottom of fuse box (only 2 wires joined to this though (the red 12v + wire for ignition ran to the red wire on firewall, the pink 12v+ for ignition hot in run/start ran to pink on firewall)

then i have connector c3 cut off the 4.8 and have the grey wire attached to fuel pump wire but cannot get any power to come off of the grey wire(no power at any of the relay terminals either) so i cannot get the fuel pump to kick in while key is in forward position... like i said i tried bypassing that by running 12v to the fuel pump and it will stay turned on as long as i hold it there but the truck won't start.

anyone have any ideas on how to go about getting the truck running? first time doing anything like this I'm a bit stumped.

[wildwilly4x4]

did you swap in a high psi fuel pump?

[cr92]

Originally Posted by wildwilly4x4

did you swap in a high psi fuel pump?

I did ..ac delco ep381 I believe was the numbers on it...60 psi, i also bypassed vats by unplugging the tbc fuse and 4 plugins under steering column while truck was running
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[Low Elco]

check all your engine grounds.... including the one at the back of each head and the one on the driver's pan rail. Dead as a stone without 'em.... ask em how I know. Can you hear the fuel pump doin' it's thing?

[cr92]

The only time i hear the pump is when i run 12v to it myself. Couldn't find any power at the fuel pump relay when i checked.. Will go through the grounds again.. And check for spark too. I bypassed vats but do you know if security disables the fuel pump or engine spark?
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[cr92]

ok so i was picking at the truck again today... still no power out of fuel pump relay.. engine only cranks over when i stick the purple wire from truck to purple wire on engine harness, no spark out of plugs, but there is power at 1 wire on each coil pack.. i connected the wire for PCM/ tranny solenoid hoping that would fix things but nope.

is the computer called the PCM or ECU? wheres the pcm and whats that for.

i don't understand why this swap is giving me the run around... as far as i could tell before starting it all i needed was 4 other connections...

am i missing anything other than whats listed?

[Low Elco]

PM ls1nova71 . Hes done a ton of these. You might also ask the mods if they can move this to the LS swap section under engine and drivetrain. Lotta knowledgeable cats over there.

[cr92]

will do... also ordered the fuse block as described on lt1swap.com

[cr92]

update... i ended up removing wire harness from truck, i contacted Adam Warren from LSXHarness.com and he talked me through the stand alone setup.. he was very patient and drew me up some simple wire diagrams for the 4 relays and 4 fuses on the block, would highly recommend his work!

connected a few wires that were coiled up for the ignition and fuel pump etc, and it fired up first click of the key!

Shout out to anyone who helped me in this thread and over on GMsquarebody forum, Adam Warren @ LSXharness.com
Brendan Patten @ LT1Swap.com

Appreciate all the help!

Cory

[Fishjeepchevy]

Any way you would have a picture of the wires or where you connected them on the 87 bulkhead