I am in the process of adapting a 1989 Astro Van 4.3 TBI wiring harness to my 78 CJ AMC V8 to build my own TBI. I have the PROM from a different AMC 304 installation in my ECM and a 305 TBI with manifold adapter and all sensors, so the wiring is all that is left. My under hood wiring is still completely stock AMC and fully functional.

My sticking point so far is the connection of the OEM Wiring and distributor/ignition to the TBI harness to power this sucker up.

Does anyone have any clear documentation how to hook this up or do I need to just get a manual, decipher the harness at the firewall connector and start trying to hook it up?

Any help appreciated.

Thanks in advance.

Originally posted by Rock Taxi
My sticking point so far is the connection of the OEM Wiring and distributor/ignition to the TBI harness to power this sucker up.

Does anyone have any clear documentation how to hook this up or do I need to just get a manual, decipher the harness at the firewall connector and start trying to hook it up?


Get the manual for your Jeep. I used a factory GM manual for the TBI wiring and a haynes manual for the CJ to do my swap ( TBI 350 into an '82 CJ7).

You should be able to rip out most of the factory CJ engine harness. Going from memory, you'll need to identify the following factory engine harness wires:
- 12V when cranking (blue wire on the starting solenoid?)
- 12V supply to the coil (goes to the TBI coil - pull the ballast resistor if you have one)
- ground :D

Pretty much everything else (except the stuff for guages) is garbage.

If you've got specific questions let me know. I may be able to help.

Ok, I gottcha on that part, what about the GM harness? Aside from the sensors, TBI and ECM, (I have those figured out I think) what wires from the harness do I hook up to power this sucker up?

Ed

Originally posted by Rock Taxi
Ok, I gottcha on that part, what about the GM harness? Aside from the sensors, TBI and ECM, (I have those figured out I think) what wires from the harness do I hook up to power this sucker up?

- Constant 12V source
- Switched 12V source (on/off with key)
- 12V when cranking
- Ground.
- Neutral safety (clutch in or neutral/park for an auto) - this is optional. You can ground it if you're not using it but I'm tld performance may suffer.

You'll also need to run wires for the fuel pump (computer turns it on/off), the vehicle speed sensor (if you're running one), the diagnostic port (to retrieve codes), and the check engine light.

There is also a circuit that checks to see if the A/C is on. If it is the computer bumps the idle up a few hundred rpm. I use this when I'm using my onboard air and when I'm at risk for stalling. Cheap mod (all you need is a switch).

That's it I think. The wiring diagrams I've seen are pretty easy to figure out. I had more trouble with the stock Jeep stuff.

www.customefis.com

has alot of tech info...