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Discussion Starter · #1 ·
I have search through the BB many times looking for information on this and have found ALOT of good information however I still have some questions. I would like to use the 4.3 TBI on my 258 and retain the Stock ignition setup. I know that there is a way to do this but have be fairly unlucky finding what I need to know. Does anyone have a wiring diagram as to how they did this? I know what hardware I need, what vehicle it comes out of, I know how to route everything, but the final install I have not clear on. If you can help me out it would be greatly appreciated. I am hoping to use a stock 4.3 chip with no mods, I dont care if it throughs some codes, I can work on programming later. Just want to be able to get this thing up and running, thanks for all of your help.


68 Posts
There is little mating to do between the OEM harness and the TBI harness. Most of the connections are intergral t the TBI ECM.. or the connections go directly from the ECM to the sensor. The points you'd need to mate are:

a. 12 Volt point always live during all Ignition Key switch modes.
Feed off the oil gauge 12 volt point
b. A 12 Volt ECM Keep alive memory feed point.
Any always live 12 volt point will do.
c. The igniton pulse to ECM point...
Take this from the OEM Tach Pulse Take off point
e. Electric Fuel pump
12 volt live in Ignition START and RUN modes.

That's really it...It's really pretty simple, and not too complicated. If you've got a wiring schematic of your vehicle these points are quite easy to find.

The other needed sensor to TBI points are:

a. O2
b. MAP
c. EGR (I find this "optional")
d. Coolant Temp Override.
e. VSS (on some units).

These points are usually straight runs to the sensor, and the trick is placing the sensor at the right point...

Email me at [email protected] if you have other questions.

216 Posts

Would this be the same for performing a complete TBI engine swap? Pretty darn soon (waiting for some fuel line parts to arrive), I'm gonna get back out to my shop and start working on my CJ again. On the list is:

Finish CJ defroster panel welding into YJ tub
Install Heater Core and Duct, also Defrost Duct
Install CJ wiring Harness and TBI ECM
Build new hard fuel lines, connect to TBI
Replace Starter, Oil, Plugs, etc on TBI engine
Wire up Engine to ECM
Splice ECM harness into CJ Harness

With the last one being the big unknown. I have a CJ Schematic, but bits and pieces of GM information (i.e. what signals & wire color require attaching to CJ harness, what signals require power/gnd signals, where the fuel pump wire is to turn on my new fuel pump, etc).

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