Some of this information may be redundant, cause I didn't really read the thread, but here is my experience with swapping TBI into my 77 stepside.
First and foremost, I didn't use any of the wiring that went through the junction block on the 89 I pulled everything out of. I personally just used the stock 77 wiring harness, then ran a seperate harness for just the fuel injection stuff. That means you do not need to worry about setting up the alternator, starter, temp / oil pressure sensors etc.
I personally switched the TBI small cap distributor out with a big cap HEI from an early TPI car. That allowed me to use the stock tach / power wiring for the distributor so I didn't have to modify my engine harness any. I did need to convert the TBI harness from the small cap HEI wiring connector to the big cap. Napa sells the tool you need to un-pin the big cap HEI wiring connector, then it is just a matter of slipping the little rubber sealing ring over the wire first, then soldering it onto the old pin after you cut the old wire off. Slip it back in, and you are done!
I also used a C130 alternator that was originally used with the TBI setup by purchasing a conversion connector from GM without the resistor (use the resistor connector if you don't have / want an idiot light for the alternator) and tying it into a diesel glow plug / water in fuel light box with new lenses I grabbed from a mid 80s car. I put a Service Engine Soon light in there, as well as a Check Gauges light.
I tied the Alternator, an oil pressure idiot light sender and engine temperature idiot light sender to the same light through a Zener Diode array which keeps different components from feeding back into each other through the common post on the light. The Service Engine Soon light is tied only into the ECM.
I also have full gauges as well, just using the Check Gauges light to warn me if I am not paying attention to my gauges on a long trip. This way if my alternator, water pump or oil pump fail, I'll have a chance to notice before serious damage is done.
As far as wiring the TBI unit itself up went, it was pretty easy. 90% of the wiring goes between the ECM and some component on the engine, so you shouldn't have to mess with any of that wiring. The only things I removed from my TBI harness was the air conditioning wiring, and the transmission lockup wiring. My truck had a 700r4 in it, but I'd already wired it up with a vacuum actuated lockup controller, so it seemed like a waste of time to try and get the TBI ECM to do a job that was already being done properly.
The only wires that I had to hook up were contained to that connector you have in the first picture in your first post (which contains the ALDL wiring, couple of battery power and ignition feeds, park / neutral feed, VSS signal feed and the Service Engine Soon light output wire,assuming I am not forgetting anything), and the fuel pump relay / fuse feed in the engine compartment (your truck may not have this, as mine came from an 89 with the power distribution block on the passenger side of the engine)
One really good way to find out what exactly needs to be hooked up is to pay a visit to
www.chevythunder.com and check out their 7747 ECM wiring pinout. I also have a couple of good diagrams that go more indepth into how each wire needs to be hooked up more so than just where. PM me if you want them.
Once all was said and done, my wiring was totally independents of the truck's stock 77 harness, I did not cut or splice anything in. It took me about 4 - 5 hours to wire everything up in a nice neat manner that was labelled for the truck's new owner, and easily disconnected if needed be.
I personally mounted my ECM on the heater box just above where the floor vent exits. I situated it in such a way that the PROM was accessible without removing the ECM from the truck, or taking anything apart. I just used some heavy duty velcro to stick it in place.
Other than the electrical, the only challenge I faced was the fuel system. The 77 was a shortbox stepside, so I kinda lucked out. I found that I was able to bolt an EFI sending unit from a newer fuel injected 88 Crewcab straight into the stock 77 saddle tank to provide myself with an in-tank pump, and still retained a properly working sending unit for the fuel gauge. For the tubing, I cut the hoses off the 89, then used high pressure fuel line which I ran between the cut off part of each hose and the tank. I then found that the stock steel braided lines were long enough to run down the back side of the engine, and beside the transmission to reach the steel lines I'd gleaned from the 89 and hooked up to my fuel tank.
Once I'd secured everything properly, it looked like a factory installation, and was at no risk of being damaged by any road hazards, exhaust or anything of the like.
One thing I didn't do on my stepside, and would highly suggest you do, is hook up a charcoal canister. The truck had a line that ran from the tank up to the front of the truck, which just vented to atmosphere under the hood. I never had any gassy smells etc when the truck was carbed, but as soon as I switched to EFI, I started to get the smell of raw fuel whenever I was driving. I tried putting on a vented gas cap, but I still had fumes.
The charcoal canister is really easy to hook up, just run a vacuum line from the canister to the nipple on the front driver's side of the throttlebody, and hook the other side up to that vent line from the tank. That will put the tank under a slight vacuum at all times, and remove any fumes that might otherwise find their way into the cab. I'd planned on installing a canister myself, but sold the truck before I got around to it.
Well, I'm sure I've forgotten at least a few things... If you come up with any questions, feel free to PM me. I'll read through the thread later on tonight and see if I can find anything myself
