3.4 V-6/T-5 Engine/Tranny Swap Phase IV

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3.4 V-6/T-5 Engine Swap Phase IV

Integrating the engine computer wiring into the Opel GT

To start this Phase off, I decided to replace the fuse panel, because it is cracked and has pieces broken off it, and fuses with aircraft style circuit breakers, similar to the panel I made for the engine test stand. No more fuses to replace, ever. So I picked up a Radio Shack plastic project box that is 8” X 6” X 3” for a reasonable price, and it has an aluminum and plastic cover, so I’ll be able to mount the circuit breakers to the aluminum plate, and put the plastic cover on top of it, with holes drilled in the plastic for the CB heads to protrude out. I happen to have a coffee can full of CBs so there was no problem with having to purchase them, they are expensive, at over $20 a piece. I also have the DESTEC wiring schematic, courtesy of J. J. Wheatley, and the four pages of computer and instrument panel schematics from Clymer and Haynes, definitely all three sources of wiring schematics are needed for this project.

Also, thanks to Otto Barsch AKA “Tekenaar” on the Opel GT.com site, who got me into using relays from his famous “Otto Start”, I decided to use a bank of relays to turn on and off various new circuits for the engine. I’ll have a relay for starting, engine start circuit, accessory position on the ignition switch, fuel pump, electric cooling fan, and anything else that comes up that will need power to operate, and I can use minimal amps going through the ignition switch to turn them off and on and have minimal power through the computer for that operation. I’ll have two rows of CBs in the box, the original seven of the GT harness and another row for the engine electrical operations and whatever else I’ll need for a power source.

O.K., on with the project.

First I removed the wiring harness completely from the car, and, it shouldn’t have had to happen, but I had to pull the gas tank as well, the PO had the fuel tank sensor wire routed wrong, so it’s sitting outside the car now. I took measurements of the connector plugs that are in the fuse panel and cut holes in the plastic box to mount the plugs in so they would lock in place, like they are supposed to in the fuse panel. That was the plan, but the RadShak box has ribs on the inside to slide bread boards into and the thickness of the ribs made it impossible to lock the connector plugs in place. Plan 2, I cut out the initial holes for the connectors into two bigger ones, one for the instrument plugs and one for the steering column plugs. As luck would have it, I had two pieces of aluminum from other project boxes laying around that would fit the bill perfectly for the plugs to mount to and then I could attach the plates to the box with small stainless steel allen bolts and self locking nuts. The only problem there was I had to cut the box where the covers screws go. It is a solid post from top to bottom of the box, and easily slotted with my Dremel and a rotary file.

So now, I have a box, with plates to lock the harness plugs in and I’m ready to put the CBs in the box so I can hook up the harnesses where the fuses used to be. Oops, there is no way to hook up the harness ends to the CBs. All the harness ends have female spade ends on them and I need ring terminals to hook up the wires to the CBs. And there is another problem, all the fuses have multiple wires going to them, some as many as three wires. Back to the drawing board, I cannot put more than one wire to each side of the CB terminals. Out of desperation, I contacted J.J. Wheatley and explained the problem, in hope that he would have a suggestion or source for vertically ganged male terminal lugs with a hole in them that I could attach to the CBs, similar to what is on the fuse panel. He suggested a couple of outlets that may have what I needed and maybe piggy-back terminal ends would be the answer. I had no idea what he meant by piggy-back terminals, but I found out and by a little bit of luck, I found a source and purchased a bag of male/female terminals and a bag of male terminal lugs with the correct hole in them. All I will have to do now is to remove the original terminal lugs and solder the new ones in their place. Now we’re cooking.

Now the first part of this phase, getting all the parts in place to build the new power panel and install the original harness in the new box and hook up the harness to the circuit breakers is ready. All I have to do is lay out the position of the connector plugs so I can drill out the aluminum cover for the CBs, but first cut and replace the female lugs with the new piggy back terminal ends. The new piggy back lugs were soldered to the existing wires, then hooked up to corresponding amperage CBs. Then each wire from the instrument panel and steering column connectors was removed, taped and identified. The connectors were locked in place in the new box and I laid out the position for the first row of CBs. I drilled the holes and attached the CBs to the aluminum plate, then attached each of the connector wires to their respective position in the connectors, then ran the wires from the harness to the installed CBs and put the whole mess together. If I was just going to replace the original fuse panel with the circuit breakers, and replace the whole plastic piece, the project box would be perfect. All I would have had to do is attach a couple pieces of sheet metal to each end on the box so it would slide into the retainer at the firewall and use the original mounting/grounding bolts to hold the box in place.

After I soldered and attached the new lugs onto the CBs and started hooking up the piggy back terminals, I found a new problem. The piggy back terminals are very soft and pliable, they break off too easily leaving the male spade lug plugged in to the female lug but separated from its attached female lug. Back to the drawing board, again. I had originally thought to use terminal strips to attach the harness wires to the CBs but I didn’t have enough room in the project box for the connectors and two rows of CBs. So in order to use terminal strips, I had to purchase another, smaller project box from RadShak, the new box is one inch smaller both in length and width, but the same depth. It would be attached, centered to the top cover of the larger box and the connector wires go through a slot from the top to the bottom box, then to the CBs or terminal strips as required. This required I relocate the CBs from the larger box to the bottom box and would still give me room for a pair of stacked terminal strips, with a large hole in the rear of the box for the main harness to be inserted. In my mind’s eye it would work because I used to have my CB radio mounted just below the fuse panel and there was ample room, once I was in the seat. It didn’t interfere with driving at all. The next plan would be to lay out a diagram of where all the wires would be attached and to include the three main circuits for the car, engine and computer. Hot all the time, starting circuit and the accessory circuit. The only problem I encountered with setting up the individual circuits was how to have the accessory circuit disconnected during starting and have only the necessary circuits activated during the starting cycle. I finally settled on using a rewired relay that would feed the starting components continually with no power to the relay switching coil and would feed the same components during the start cycle by energizing the switching coil of course there would be no power without the key being turned on. This was done by having the center or contact pole of the relay feeding the start circuit with power from the accessory circuit in the normally open side of the relay and feeding power from the battery to the switched or closed side of the relay during the start cycle.

Attached is a pic of the layout of the wiring hookups from the connectors to the circuit breakers, the terminal strips and to the various components of the circuits, via relays if necessary. I didn’t number the terminal strips because it wasn’t necessary for what I was doing at this point.

That’s how it looked on paper, and this is a rough idea of how it was going to be. Everything on all the schematics was checked and double checked and I found I had made a few duplications in the original drawings that set me back a couple of days in figuring everything out. Finally all the drawings made sense and I started to put it all together. As hard as I tried to straighten out the wires to prevent another rat’s nest, it never worked out, some wires just didn’t seem to get straightened out. I mounted all the relays and both headlight relays on the back of the upper box, the seatbelt buzzer and relay, the ignition buzzer were mounted on the bottom box.

I had done what I had wanted to do. Have all the connections, CBs relays and buzzers in one central location, in place of the original fuse panel. All that remains now is to splice in the relay signal leads to the fan relay, pump relay, AC relay, and the power out leads of those relays, along with the computer power leads to the computer, ignition module and fuel injectors. Oh yeah, I’ve got to put the harness back in the car. Still a rats nest, but not bad considering I’ve got 11 more fused circuits than original and a lot more wires to route to the computer so everything will function as it’s supposed to.

Just prior to OMC, I installed the engine/tranny and all the peripheral stuff in the car and towed it up for the picnic behind the motorhome. One thing was very clear, the electrical power panel would not work as it was supposed to. The relays were hanging too far down to operate the clutch and brake pedals safely, and I wasn't too happy with the placement of the CBs on the bottom of the box. So it's back to the boards again.

I got another small box from RadShak and modified to to accept the CBs in front of the box and mounted the relays around the side and higher up on the rear of the box. This gave me more room under the box and, because I had to relocate the CBs, I found I could put two more in the box if I laid them on their sides, so instead of 2 rows of 9, I now have 5 rows of 4, a fair good trade-off.

The real fun came when I started to integrate the circuits between the engine computer and the car. Some of the wiring on the engine would go straight to the GT harness and others would go in a roundabout way from engine, to the car circuitry then to the computer and back to the engine. I spent days tracing out the circuits figuring out where they start and end up, then hours on the computer building spreadsheets to be sure when I cut and splice the wires would end up where they were supposed to go. Having the other ends of the computer harness plugs was invaluable for this. I used up all the connectors and had to get more from RadShak to finish the harness from the engine to the car. I ended with about 50 more circuits than the original GT harness has.

A couple of side notes here, the T-5 tranny only came with an electrical speedo output, so I had to get a box that converts electrical impulses to mechanical output from "Cable X" in Arkansas. I posted numerous queries on the site and finally found P.J. Hall had made up a circuit board to convert the GT tach from a 4 cylinder to a 6 cylinder for Mike Pilkenton's original V-6 swap. P.J. was very helpful, sending me two boards and schematics/directions. When I got one built, I sent the second board to Nathan Acree along with the spare electrical components for his V-6 swap.

During the integration process I ended up cleaning up the engine harness, rerouting everything from the top of the engine to below the plenum and along the sides of the motor. This cleaned up the look of the engine very nicely. Now, as soon as I'm done with a few other Phases, the engine will go back in the car, hook up the battery, and if I can keep the "magic smoke" inside the power panel boxes, it'll be ready to start up in the car, FINALLY!!!