I have a write up I did about 10 years ago. It was on an old CJ 258 but should be about the same. I will try to paste it here. If the wiring pin out chart doesn't do right I can PM this word doc.
GM 4.3L TBI on AMC 258
I wanted to fuel inject my old 1973 CJ5 258. Although I had my Weber tuned well it would still give me fits in extreme angled situations. The solution was fuel injection. The thought of ******* out $1200 for a Howell kit was not a possibility although they are well engineered and supported. I had seen write-ups on getting parts from a 4.3L GM but no completed projects. So not being particularly bright I decided to give it a whirl. I had a lot of help that I’ll list at the end of this. First, what I got from the junkyard.
Donor Vehicle: 1989 S10 4x4 Blazer with 4.3L :
• ECU-passenger side under dash behind lower panel.
• Harness-don’t forget matting plugs from other harness. The fuel pump relays along with another relay (I used it for the ECU power) are on the driver’s side fender so pull these wires out of main harness as well.
• ALDL terminal-drivers side under dash.
• All sensors hooked to the ECU harness-get them all even if you don’t use them.
• GM 8 pin ignition module-in the distributor.
• Harness from coil to ignition module.
• Breather assembly
• Throttle Body (including some of the fuel lines)
(All for $100)
• Throttle Body to Jeep 1 barrel carburetor adaptor.
• Fuel pump mount, filter mounts, etc.
• Fuel Pump
• Throttle Body base gasket
• Two 1 barrel manifold gaskets
• Fuel Filter
• Air cleaner filter
• O2 sensor (to lazy to crawl under and it would probably break)
• Temperature (old one broke when I tried to take it out)
• Various fuel line and fittings
• Wiring terminals, wires
• 12 VDC red light for the “Check Engine” light.
(All for around $160) (See links below TBI.docfor specific part numbers)
• O2 sensor bung welded in my exhaust system (Meineke). ($28)
After pulling parts I spent some time with some wiring diagrams (I’ll attach what I can) and traced down/marked wires. This allowed me to pull out wires I didn’t need. I ended up needing to extend some plugs and shorten others once it was in the Jeep but to me this step was necessary to clean things up prior to trying to install.
The next step was removing the old fuel system (disconnect the battery). Once this was out of the way I started with the new fuel system installation.
1. You need a supply and return line for fuel injection. Later model Jeeps can typically use one of the tank vent lines as a return. I have an under the seat plastic tank which required me to drill and tap a 1/8” NPT thread and install a fitting. The S10 return is 5/16 so I installed a 5/16 barbed fitting. I made a bracket to hold my filter under my seat. I might make some people nervous but the tank is under there already. Then I drilled a couple holes and ran the fuel lines underneath. I mounted the fuel pump on the inside of the frame rail under the tank. I then took the lines forward to the passenger side fender.
2. Mount the adaptor to the intake. Then the throttle body to it. With my design I had to test fit it and cut the intake studs off so they would be flush with the nuts. Use some Red Locktite so the nuts don’t come loose. I mounted my throttle body with the fuel line facing forward. This made the accelerator cable much simpler for my application. Then coupled the fuel line. The port between the fuel lines is the MAP connection. Don’t hook anything else to it. On the other side is the EGR (biggest), smaller vacuum lines to each side, on one ¼” line kind of central. This is the one you want your distributor vacuum hooked to. I plugged everything but the MAP because I don’t have pollution control devices & I have a HEI so I will let the ECU control timing.
3. Sensors need mounting next. The temperature sensor went on the block on the driver’s side toward the back of the engine. There is a 3/8” plug. Your going to get coolant when you take this out so put a bucket under it. Have the sensor already pipe doped and swap them quickly. The O2 sensor can be put in when you get the bung added to the exhaust. Do this prior to making your Jeep immobile. I’d wait on the MAP to mount it until you get the harness installed. It does need to be at least slightly higher than the base of the throttle body and the vacuum port should be pointed down.
4. Next is installing the harness and hooking the engine up. Find a safe place right below the heater box on the passenger side fire way. The grommet on the harness measures 2 3/8” diameter. I used a 2 ¼” hole saw which worked fine. They always seem to drill oversized. Once the harness is in the hole you can start laying it out on the motor to see what needs to be altered and hook it up. You’ll need to run some stuff inside to the ECU. I drill another hole (5/8” dia.) for key on + (make sure it stays on during cranking), crank signal from the starter solenoid, + always for the relays & ECU, fuel pump wires, and the fuel pump relay wires (7 wires).
5. Move inside to start the ECU hook up and mounting. Where all this goes is personal choice. I opted to remove my glove box and utilize this area for electrical stuff. Modifying the stock ECU bracket I mounted the ECU on its side running toward the drivers side so I could see the plugs in the glove box. I made a plate out of some 1/8” x 4” steel to mount the four-fuse holder and two relays. My check engine light is above the ECU in the dash. The two relays are for the fuel pump and the key power to the ECU. The fuses are 20 amps for power always to the relays and the ECU, 10 amp for key power to the ECU from the relay, and 10 amp for the crank signal to the ECU.
I used the 8-pin module from the S10 to run my big cap HEI. You of course have to remove the 4-pin stuff and run wire from the pickup to the 8-pin. I mounted the module on the firewall. I understand that a 7-pin module will fit inside the distributor but the 8-pin was what I had and it’s easier to work on. You have to lock the vacuum and mechanical advances in order to let the ECU control timing. The GM 8 pin ignition module is necessary so you can step down the AC wave supplied by the HEI pick up to a DC pulse of the proper voltage to the ECU. Otherwise it won’t work and you’ll probably fry the ECU.
Here is a drawing of the 1 barrel manifold throttle body adaptor I made:
This is the ECU pin assignment/wiring aid:
Pin Color What Where Notes
A1 grn/wht fuel pump trigger fuel pump relay plug 20 A fuse
A2 grn/blk extra A/C clutch
A4 gray EGR relay ground Tape off
A5 brn/wht Service engine light ground SES light-10 pin plug
A6 pnk/blk 12 V key (+) key-10 pin plug
A7 tan/blk extra A/T down shift
A8 orn ALDL serial data (E data) 10 pin plug 12 pin serial plug
A9 wht/blk ALDL serial data (B data) 10 pin plug grounded gives codes to SES
A10 brn VSS speed sensor Tape off
A11 blk MAP ground MAP plug
A12 blk/wht System ground (A12) (-)ground
B1 orn 12 V always (C16) (+) battery (fp plug)
B2 tan/wht fuel pump signal fuel pump relay (on) plug
B3 blk/red EST reference dist plug ECU timing only
B5 ppl/wht EST high reference tach signal-dist plug AC signal-needs to 5 VDC
B7 blk Knock sensor to ESC C14 (+5 V)
B8 dk grn A/C signal Tape off can be used to increase RPM
B10 orn/blk Park/Neutral switch Tape off
C2 x EAC solenoid
C3 IAC TB plug
C4 IAC TB plug
C5 IAC TB plug
C6 IAC TB plug
C7 x High Gear Switch signal
C9 ppl/wht Starter crank signal start solenoid-10 pin plug 10 amp fuse
C10 yel temperature temp plug
C11 lt grn MAP signal MAP plug
C13 dk blu TPS Sensor TB plug
C14 gray 5 volts for MAP & TPS MAP & TPS plug
C15 grn not used
C16 orn 12 V always (B1) (+) battery
D1 blk/wht System ground (D1) (-)ground
D2 blk sensor ground engine ground
D4 wht/blk EST control dist plug ECU timing only
D5 tan/blk EST bypass dist plug ECU timing only (disconnect for timing)
D6 tan O2 ground O2 sensor
D7 ppl O2 signal O2 sensor
D14 lt grn Injector "B" ground injector plug(other yel) 10A fuse
D15 blu not used
D16 blu Injector "A" ground injector plug(other red) 10A fuse
The guy’s (especially Bill) at the International Harvester Truck Forum are extremely knowledgeable on getting this stuff to work. Here are a few links there:
Here’s Howell’s Book:
Some GM manual pages:
A Jeep guy writes:
Here’s a link to the ECU codes:
Finally, a couple Jeep Forum Guys were great help and a good sounding board for my farfetched ideas. By forum name jadams68 & rjcj8. Here’s a link to that forum
So, for $300 and a couple lost days my Jeep will now run upside down. This process was on a 258 but I plan to do my buddies AMC 304 next. The steps would be the same for about anything you wanted to fuel inject. Oh, I almost forgot. I installed a big Emergency Stop button in the middle of the dash.