Bare minimum needed to run engine
 

What is the bare minimum needed to run a factory engine using the factory computer? I know every wire coming out of the ECU is not needed and I have heard of people stripping the factory wiring harness and only using a few of the wires. Anybody have any specifics on this? The reason for this is I will eventually end up with a stand alone controller and intake. I currently have a weber sidedraft and would like to avoid replumbing/wiring when I go back to fuel injection.

What year car/ECU?&nbsp It is vastly different for 1986-1988 Zenki versus 1989-1991 Kouki vehicles...



-Ted

For a series IV. I have a questionable harness, ECU and engine from an 87 N/A automatic. Was considering using that till I get the actual stand alone controller with a new wiring harness. I'll possibly be using it in my FP car instead of the weber.

Ack, automatic makes it a bitch, as some of the auto trans is controlled by the ECU, I believe.

Otherwise, it's just...
TPS
water thermo
air temp
ignition in/out
fuel injectors
air flow meter
grounds

I believe everything else can be gutted.



-Ted

I have the FSM available for reference on wiring. Only using the needed wires off the factory harness, cutting away the unneeded wires, would it be worth while to go this route? I'll be using manual trans so the auto trans part of the ECU is not needed, but could cause a problem if it doesn't like that. I'm just trying to find the least expensive route to get my car running for the first race. I'm about to reinstall the engine in the next week or two and needed some guidance before I get to the wiring part again. Right now I'm leaning toward the carb again since its a know good piece. When I get to installing the stand alone I'll have a new harness to deal with and will only need to rework the fuel delivery some. Are you confussed yet Ted? I don't blame you.

That should be it.&nbsp I know what you're doing, since I've worked on a similarly prepped FC like yours (pseudo-ITS)... :)

Cut all the wires out, but be careful with all the + voltage ones - these should be "capped" to make sure it doesn't arc to ground.




-Ted

Thanks Ted. I'm going to think about it some more. I've got almost everything I need to go either way but can't make my mind up. Probably going back to the carb since its a know working setup. Messing with all the wires in the factory harness gives me a headache just thinking about it.

I was looking at an automatic '87 (N/A of course) and was working on removing the ECU and engine wiring harness. Two of the three yellow plugs (the medium sized one and the small one) went to the engine bat through the firewall, and went to the engine and MAP/AFM and a couple other things that aren't important - that was easy to separate from the main loom. I noticed that the connector for the vacuum switch (automatic only) didn't go through this loom, but instead wrapped around the front of the car and along the driver's side. The only other stuff on the engine loom that didn't go to the ECU were two wires, one white and one black (both with red or brown stripe) they went to the alternator. Snip snip! :D So the engine harness is now separate, as far as I can tell.

The third, long yellow connector goes along the firewall to the driver's side of the car. Huh? Possibly only really related to automatic trans? (Dash is out of car but I couldn't get the blend door assembly thing out, there's a "mystery bolt" hidden somewhere) I know SOME wires have to go to the I/P (tach, speed sensor, ETC) but I noticed that the coils go on the driver's side part of the loom. Ugh... that means at least the coils are on the big long connector. Anything else important, like CAS or ?

I'm probably going to be putting the engine in my GXL (also automatic) but I think it'd be neat to have an EFI setup to tinker with and adapt to a 12A or something just for gits-n-shiggles... so only a "bare minimum" is necessary. BTW I got so depressed looking at the MILES of loom on the driver's side that I just cut the coils out... probably much easier to make new wire than to go through and separate all that mess from the loom!

peejay - Your absolutely right about getting depressed about the miles of loom. I've decided to go with the carb setup for now. I'll make my own wiring harness later for the starter and guages. The stand alone controller has its own for the injectors and computer. Getting rid of the factory harness saved 25#. I will probably add back no more than 5# of wire.

Hmm... maybe then just make a manifold and stuff a carb and dizzy on there until the wiring is sorted out.

I know what I've said about carbs in the past :) But moving back into an emissions part of the state would mean emissions compliance, therefore an engine swap must retain the smog equipment. I love carbs but you can't beat EFI for emissions purposes, the control is so much finer.

I am planning on doing this also. I was wonderin if you could post some pics of the wiring harness and what you kept if you have any
thanks

Actually finky, I'm going to make the parts that I need. I'll end up with a stand alone computer which has its own wiring harness for the sensors needed to run the engine. I'll only need to wire up the auto meter guages, tachometer and starter.

i'm in the process of doing the same gutting and going carb, are all the dash sensors wired through the ecu or can i retain certain wires for tach, volt, water temp, oil press...ect basically all in the console.