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Good Bye SonomaST
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7,145 Posts
Discussion Starter #1
ok i have found threads that touched on the subject, but never answered what i was seeking.
I have a 91 with a 2.8, i want a v8, but am waiting on doing a LS1 swap, but i want a v8 now! i can rebuild a carb'd motor fairly easily and cheap.
I don't want to tear out all my wiring because i will need it once i put in the LS1 to hook Jared's harness to. so to do a carb'd motor, i will need my VSS, to hook into the tranny, i will probably run HEI, so i will need, power, ground, and what else for it. im probably going to leave the fuel pump alone and just put a regulator with a return on it. and i will use my oil pressure sending unit on the v8. but thats pretty much it right?
i want to beable to use my stock guages and such, but how am i going to wire my oil pressure switch, i guess i could just put it in the v8 right? thats really about all i can think of, with just those wires i can still leave the ECU under the dash(i will have to for the VSS and some other stuff).
How do i ditch the injectors? i suppose i can unhook the wires somewhere besides on the injectors themselves. as you can tell im not exactly sure where im headed, im kinda in the right direction, but i need help getting there. if i can do this for a reasonable amount of money, im gonna put a v8 in.
if i had a damn 4.3 i would just put a TBI motor in and roll out, haha how hard is it to put a 4.3 harness and computer in?
 

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Good Bye SonomaST
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7,145 Posts
Discussion Starter #4
Very easy IMO.......and just as easy to swap in a 350 TBI with the 4.3 harness.
You forgot temp sending unit the volt guage should be a given. Tach (if applicable) would need calibrated.
lol thats waht i meant, swap in a 4.3 harness and computer, but use it to run a v8.
i was hoping you would reply!
and yes i forgot those, im writing this down as im seriously considering this. i had said the only v8 that will go in the truck will be a LS, but im to the point where i just want it to have some balls until i can get the cash to do a LS swap properly.
so what would be involved in swapping to a 4.3 harness? unplug computer, unplug factory harness, then reverse? HAHAHAHAHA, im dreaming sorry
 

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11 second station wagon
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2,921 Posts
I would get from the corner connector ( DS firewall) to the ECM (Under the dash entering in the PS firewall and computer) wiring from a 4.3 with the same options as the chassis. In other words if your truck is 2.8 automatic trans..... get one from a 4.3 automatic. 5 speed..... ditto. C/C...Delay etc....The more similarities.... the better. This will lessen wiring problems (if any) as you go along.
 

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Good Bye SonomaST
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7,145 Posts
Discussion Starter #6
ill check into this, but still anyone offer up ideas, jared if u read this, post up buddy
 

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Good Bye SonomaST
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7,145 Posts
Discussion Starter #7
ok so another question. what are the main wiring differences in a TBI 2.8, and a TBI 4.3? They have the same sensors and modules dont they? I have read a little on this before but couldnt find much info on it either. Would it just be a matter of swapping a few wires around and adding a couple of sensors or something?
 

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Good Bye SonomaST
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7,145 Posts
Discussion Starter #8 (Edited)
This is the wiring schematic for a 91 2.8 s-truck
ECM Wiring Diagram (Part 1 Of 3)


A8 = SERIAL DATA. A9 = DIAGNOSTIC TEST. A12 = SYSTEM GROUND. D6 = OXYGEN SENSOR GROUND. D1 = SYSTEM GROUND. C9 = CRANK SIGNAL. D7 = OXYGEN SENSOR SIGNAL. A11 = SENSOR GROUND. C11 = MAP SIGNAL. C14 = +5V REFERENCE. C13 = TPS SIGNAL. D2 = SENSOR GROUND. C10 = COOLANT TEMPERATURE SENSOR. B8 = A/C SIGNAL. A2 = A/C RELAY CONTROL.

ECM Wiring Diagram (Part 2 Of 3)



C5 = IAC "A" HI. C6 = IAC "A" LO. C4 = IAC "B" HI. C3 = IAC "B" LO. A6 = IGNITION. D16 = INJECTOR DRIVER. D14 = INJECTOR DRIVER. B3 = REFERENCE LOW. D5 = BYPASS. B5 = REFERENCE HIGH. D4 = EST. B1 = 12 VOLTS. C16 = 12 VOLTS. A1 = FUEL PUMP RELAY DRIVE (12V). B2 = FUEL PUMP SIGNAL.

ECM Wiring Diagram (Part 3 Of 3)



A5 = SERVICE ENGINE SOON LIGHT CONTROL. A7 = SHIFT LIGHT (M/T). C2 = EAC SOLENOID. A6 = 12 VOLTS. A10 = VEHICLE SPEED SENSOR. B7 = KNOCK RETARD SIGNAL (ESC). A6 = 12 VOLTS. A4 = EGR CONTROL.
This is a wiring schematic for a 91 4.3 s-truck
ECM Wiring Diagram (Part 1 Of 4)


A8 = SERIAL DATA. A9 = DIAGNOSTIC TEST. A12 = SYSTEM GROUND. D6 = OXYGEN SENSOR GROUND. D1 = SYSTEM GROUND. C9 = CRANK SIGNAL. D7 = OXYGEN SENSOR SIGNAL. D2 = MAP GROUND. A11 = SYSTEM GROUND. C10 = CTS SIGNAL. C5 = IAC COIL "A" HI. C6 = IAC COIL "A" LO. C4 = IAC COIL "B" HI. C3 = IAC COIL "B" LO.

ECM Wiring Diagram (Part 2 Of 4)



B8 = A/C SIGNAL. A2 = CLUTCH CONTROL. B1 = 12 VOLT. C16 = 12 VOLT. A1 = FUEL PUMP RELAY DRIVE (12 VOLT). B2 = FUEL PUMP SIGNAL.

ECM Wiring Diagram (Part 3 Of 4)



A5 = SERVICE ENGINE SOON LAMP CONTROL. C7 = HIGH GEAR SWITCH SIGNAL. A7 = A/T TCC CONTROL GROUND. A10 = VEHICLE SPEED SENSOR. A4 = EGR SOLENOID (M/L). A4 = EVRV SOLENOID (S/T). B10 = PARK NEUTRAL SWITCH (A/T). A6 = 12 VOLT IGNITION. B7 = KNOCK RETARD SIGNAL (ESC).

ECM Wiring Diagram (Part 4 Of 4)



A6 = 12V IGNITION. D16 = INJECTOR DRIVER. D14 = INJECTOR DRIVER. D4 = EST. B5 = REFERENCE. D5 = BYPASS. B3 = REF. LOW.
It all pretty much looks the same, there are a few differences here and there, but they appear to be very small, nothing a little work couldnt fix, but there is also some wiring in there for a M/L line of vehicles so don't let that confuse u.
tell my what you guys think. from what im seeing the wiring at the ECM is exactly the same, so that leads me to think you can just swap over ECM's.
 
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