Project ROKTOY - Wiring & Gauges

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Short Cuts

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By: Jay Kopycinski - 2/2003

The wiring for this project can be divided into two major sections: engine control and all other chassis electrical. The engine wiring consists of all the TBI fuel injection system which includes some engine sensors and distributor function. Other wiring includes engine starting and ignition, engine sensor and gauge wiring, lighting, and winch cabling.

When I purchased my '94 TBI engine I also got the complete underhood harness and my original intent was to use this harness for engine control, after I dissected it and deleted all the wiring I didn't need. However, I found that GM changed the computer configuration about 1992-1993. They went from a two-connector ECM setup to a three-connector one. The older style is the one commonly used for TBI conversions. Rebuilding the harness to fit to the older style computer was becoming difficult and I would have had to source the other style ECM connectors. About the time I was dealing with this I ran across a deal on a Painless TBI harness, so purchased it.

The Painless harness worked well. I just found that most all the sensor wires were about 4 feet too long for my application. I shortened most all of these harness wires to better fit my close proximity of the ECM to my engine. My ECM is located on the passenger side firewall, on the cab side. I used the common 1227747 ECM, a manual tranny truck unit. My only engine mods were the addition of a 1" TBI spacer and the Holley Flowtech headers, so I chose to use stock V8 PROM and Cal-Pack chips.


What to do with all this wire?	Tearing into the Painless harness	More wiring...big mess now	Completed engine wiring at firewall

I needed to run power cables from the battery to the starter, and winch and ground cables to tie all the major components together. I mounted the battery under the dash area on the tranny tunnel area. I ran the positive battery cable to a Wrangler Power Products feed-thru on the firewall. On the other end of the feed-thru, I ran cables to both the starter and the winch solenoid pack mounted on the passenger front corner of the chassis. In most cases, I made connections using fine-stranded welding cable and copper lug ends. Ground cables connect the battery to the tube chassis, then to the engine block, and finally to the winch body.


Battery mounted under dash	ATC fuse panel above battery	Another view of fuse panel	ECM mounted at passenger firewall	Winch solenoid on chassis

For the chassis wiring, I started with an ATC style fuse block from Wrangler Power Products which I mounted directly on the occupant side of the firewall. One portion of the block is connected straight to battery power and is constantly hot. The other portion of the block is connected to a relay that supplies battery power when the ignition switch is in the START or ON position. From these fuses, all the power is run to the various circuits.

I used several colors of wire and made up a wiring schematic to record all the circuits, should I need to do any modifications or troubleshooting in the future. Almost all connections were mechanically spliced, soldered, and then covered in shrink-wrap tubing. Finally, the wiring bundles were encased in split-loom tubing for protection.

To monitor system vitals, I used Nordskog Pro Series Analog gauges. I chose to install 2 5/8" water temp, oil pressure, voltmeter, and fuel level gauges. Additionally, I added a large face 0-6000 rpm tachometer above the steering wheel. These gauges are microprocessor controlled and drive the meter needle with digital stepper motors.


Pattern for instrument layout	Assembling instrument panel	Completed instrument panel	View from under the "dash" area	Top overall view of dash


Taillight wiring & CO2 line	ARB solenoid on firewall

The wiring portion proved to be time-consuming and tedious, but having a good plan and knowing what was required to put the whole rig together made the job proceed fairly smoothly. Fortunately, when I fired it up, all worked fine.

More to follow........