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Howell TBI Installation

(Note: These procedures work with model year 1983 through 1986 Jeep CJ-7s)

I wrote this procedure in order to more fully document the removal of the original wiring harness in my 1983 CJ-7. I found the Howell documentation to be confusing in the section where it describes OEM harness removal and I hope this saves you some time.

1. Do all the Howell steps up to and including removal of the original engine computer, behind the glove compartment. The computer, like the original BBD carburetor, will no longer be needed so you may discard it.

2. Feed the computer’s wiring harness through the firewall into the engine compartment. Leave it on the engine for now. Unwrap the wires. Note the duct tape that AMC used when wrapping splices. You will have to cut the firewall grommet. Save the grommet because we will reuse it later with the new wiring harness.

3. The Duraspark module is located under the radiator overflow reservoir. It might be easier for you to remove the reservoir and then remove the Duraspark module entirely. There are two connectors on the module, disconnect the one that attaches to the computer wiring harness. You can double check this by following the path of the wires, the one you don’t want to pull out and remove is part of the other wiring harness that goes into the firewall on the driver’s side.

4. Leave (take note of the location) the intake manifold heater. Two wires, hot and sensor, these will be reconnected. On my ’83 Jeep these two wires came out of the other harness, the one that remains.

5. Disconnect the wide, flat, six-wire connector next to the brake master cylinder. You are not going to need any wires out of this for anything so you could probably cut the connector itself out of there and leave the area clean. I left mine in.

6. Now pull the entire harness towards the passenger side. Drape the harness over the battery.

7. Remove the OEM diagnostic plug. This is the plug that is located either on the inside of the fender or on the battery tray - I’ve seen it in both places on mid eighties CJ’s. Drape that length of wire over the battery also, as you won’t need that after this is all over either.

8. Disconnect the wires going to the distributor. Be careful of the connector, it’s hard to disconnect without breaking the plastic tabs. You will be saving and reusing this.

9. If the green wire coming off the coil has a connector you can disconnect this as well. You will be saving this wire also. On my Jeep there was no connector, so I had to cut the wire as described below. On every other Jeep I’ve seen there’s been a connector.

10. Wires to cut. Here’s where things get interesting. The entire harness is going to be removed from the Jeep, but I wanted to cut as few wires as possible. Remember that a couple of wires are going to be put back in so don’t be too brutal.

A. Cut the two black ground wires that attach to the engine block. Leave about 8 inches remaining, as these will be re-used for grounds later.

B. Cut the orange and purple wires coming from the distributor connector and going to the wide, flat connector that attached to the computer. Cut these about 8 inches back from the computer connector to give you some working length.

C. Cut the green coil wire. Leave as much length as possible. This wire comes from the Duraspark end. Note - as mentioned above, I had to cut the wire on mine, as there was no connector. If you have a connector you can just disconnect. You could also remove the wire from the coil itself, but I didn’t go to that much trouble.

11. Now pull all those freakin’ wires out of there and throw the entire harness on the ground! None of this mess is going to be reused, well, with the following exception:

Separate the distributor to Duraspark wire set. You will be reconnecting this later.

12. If you haven’t already done so, unbolt the Duraspark module to get access to the wires coming out of it and going to the connector. Removal makes it much easier to get to, because we will have to splice into the purple wire between the module and its connector.

13. Time for a quick break. I prefer Mountain Dew. Refreshed? OK - back to work.

14. This step is optional, Howell makes no mention of this:

A. I noticed that Howell uses the throttle linkage bracket for the ground for their wiring harness. This just doesn’t seem right to me, so I recommend making a more solid ground to the engine block itself. So…

B. Connect one of the remaining engine block grounds to the throttle linkage on the intake manifold. You may have to splice an extra piece of wire to reach it. Now the Howell system is grounded directly to the block. This just seems to make more sense to me. Now back to our regularly scheduled install procedure.

15. The following steps are performed out of the engine compartment. I stretched the wires out on the driveway ahead of the Jeep to make things easier. We are going to connect the distributor to the Duraspark module by making a new mini-harness.

A. Connect the two orange wires together.

B. Lengthen the purple wire to go past the Duraspark connector. You will need this extra length because you will be splicing into the purple wire that is on the Duraspark module side. Note how there are four wires going into the connector and only three coming out. The purple wire you’re holding is the fourth.

C. Connect the green coil wires together. (Unless you didn’t have to cut as described above.)

16. Now install the mini-harness into the Jeep. You can rough it into place by using zip-ties following the path of the original harness. Now is also a good time to mount the MAP sensor to the firewall, if you haven’t already done so.

17. Connect the purple wire from the distributor to the purple wire going to the Duraspark module. I put a plug in mine in case I have to remove the module at a later time. Reconnect the main plug(s) and tie everything in place.

18. Reattach the Duraspark module to the fender and reinstall the overflow reservoir.

19. If you haven’t already done so, screw the Howell-supplied coolant sensor in the intake manifold.

20. Now comes the fun part: installation of the Howell harness. I fed mine into the dash from the engine side, so the computer connectors, the power lead with fuse block, the diagnostic connector, and the CES light are inside. Everything else stays in the engine compartment.

21. Continue with Howell’s instructions, you’re on the home stretch now. Good Luck, and I hope these additional procedures helped.