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Bought the car last year and have started trying to clean up the engine area this summer.
The Previous Owner(s) disconnected/removed the AC and most of the smog equipment - trying to play catch up trying to figure things out on this car as a lot of the wiring has been cut/spliced along with equipment changes.
First off, the carb has been switched to a Holley Street Avenger 570, and Edelbrock TES Headers were added to the car.
Currently I am trying to figure out how to reconnect the 02 sensor - I have been searching the board and believe I found a thread that indicated the O2 sensor wire is purple, and is supposed to be in a loom on the drivers side of the engine with a green wire that leads to a temp sensor between sparkplugs on drivers side of engine - no purple wire there!
So I tried to trace backwards from ECM - I looked at the ECM wiring loom coming from the passenger side - and of course I found a lot of wires disconnected. There are exactly 3 different connectors not connected to anything, and low and behold an pinkish/purple cut wire (not sure if this is the O2 wire I am looking for).
Anyways, I am attaching two pictures - one is the cut wire from the 02 sensor, and the second is a picture of the disconnected wires on the passenger side - you will see 3 connectors not connected to anything and a solitary puprly/pink wire that is just cut and doing nothing.
I am somewhat a newbie when it comes with anything electrical or emissions related so any HELP is totally appreciated.
Unless you are swapping back to the computer controlled carb and distributor, you don't need the O2 connected. The same probably applies to the rest of those wires. You need the starter wiring, alternator wiring, distributor power, etc but all the emissions equipment and old sensors etc arent doing much without the computer.
Your engine has 2 complete, discrete, non-interconnected main wiring harnesses.
One comes from the bulkhead connector below the brake booster. This one has all of the stuff required to run the engine proper, such as was the case in the 60s and early 70s. Starter, alternator, gauges, ignition, ... all in that one.
The other comes from the pass side, out of the fender area between the blower motor and the strut tower. It contains all of the computer-related stuff: O2 sensor, TPS, CTS, KS, AIR control, MCS, MAP sensor, etc.
That 2nd one, you can remove in its entirety, WITHOUT CUTTING ANYTHING (that isn't already sodomized). Start at the ECM itself, under the dash on the pass side, where most other cars have their glove box. Unplug it, remove the retainer that holds it in the windshield cowl behind the pass side kick panel, and pull it through to fender well. Then CAREFULLY AND METICULOUSLY, WITHOUT TOUCHING YOUR DYKES, follow each and every wire to its destination, and unplug it and remove carefully. Put the ECM and the ENTIRE harness thus obtained in a box and store it in your attic or wherever.
There are several other much smaller harnesses associated with specific subsystems and accessories. Cruise, HVAC, wipers, in particular. No need to disturb any of those.
Put your A/C back. If there's ANY ONE THING that distinguishes those trailer-trash POSs you see rolling down the road sometimes that people make fun of and that members of the opposite sex RUN AWAY FROM when they see it coming, from an older DESIRABLE car, A/C would be it. Whether you think you "need" it or not, it's the biggest factor separating a "nice" car from a hooptie. Put it back.
If your distributor doesn't have a vacuum advance can, you need to replace it with one that does, ASAP. Put the non-vac-adv one in the box with those other computer-related things against some unforeseeable situation in the future when you might need it again.
Thanks for the information - I plan to put the AC back once I get everything running smooth. I have some noobie questions - please bare with me.
Is there anything in the harness you described connected to any gauges on the dash? The two that come to mind are the temperature gauge and the thing that started this little drama for me which is the engine light. The engine light is currently on and I thought it was because of the o2 sensor - but as you pointed out my carb is not connected to the computer so that likely wouldn't do much. The engine light wasnt on before so I was jus trying to figure out how to get it off again - but now that I think about it the 02 has always been disconnected so that isn't my problem. Any ideas what might be causing the light to come on? I will look into what type of distributed I have and figure that out - thanks for the advice - need all the help I can get. I'm good at maintenance and replacement of parts - crappy trouble shooter just learning.
The Check Engine light is driven "Off" by the ECM... which is to say, it has a lamp driver, external to the ECM, that turns it on ALWAYS, unless the ECM tells it to turn off. If you don't like it glowing, take out the bulb.
The temp gauge is in the harness that's been used in cars since they started using electric temp gauges in the 50s. Not related to the ECM in any way.
Is there any chance to find a diagram of the wires that come from the bulkhead below the brake booster? Since those are the wires I need to make sure are connected, I would like to try and locate those. As far as the ecm wiring goes, I am attaching a diagram that shows a WHT/DK GRN wire running from ECM to service engine light? is this the wire that tells the check engine light to turn off? if so, does anyone know if the system needs to send voltage to the indicator, or shut off voltage? Also could anyone confirm what WHT/DK GRN means? Appreciate the help.
I know this is going to sound kinda .... yeah .... but, the easiest way to locate the wires coming from the bulkhead connector, is to start at the bulkhead connector, and look at them. It's really not that hard.
But that's a bunch of unnecessary work. Don't bother. The wires you want to remove are, as someone mentioned above:
That 2nd one, you can remove in its entirety, WITHOUT CUTTING ANYTHING (that isn't already sodomized). Start at the ECM itself, under the dash on the pass side, where most other cars have their glove box. Unplug it, remove the retainer that holds it in the windshield cowl behind the pass side kick panel, and pull it through to fender well. Then CAREFULLY AND METICULOUSLY, WITHOUT TOUCHING YOUR DYKES, follow each and every wire to its destination, and unplug it and remove carefully. Put the ECM and the ENTIRE harness thus obtained in a box and store it in your attic or wherever.
Since those DON'T come from the bulkhead connector, you won't be disturbing anything that DOES come from the bulkhead connector.
Again, this is really just not that hard.
is this the wire that tells the check engine light to turn off?
Yes you could call it that: if you disconnect it, the light will stay on permanently. Which is no biggie... once you disconnect all that other stuff having to do with the ECM, the light is meaningless at best anyway, might as well just pull the bulb. Like someone already mentioned.
Also could anyone confirm what WHT/DK GRN means?
That would mean white w/ a dark green stripe.
Earlier I said this is not hard... I was wrong, I take that back. What I should have said is, this is EEEEEEEEZY. It's just electricity. Probably the simplest subsystem of a car, with the possible exception of the cooling system.
Thanks again for all your help - much appreciated as I'm totally just trying to figure this car out. My last set of dum questions for this post anyways
I'm going to try and do what you have mentioned this weekend. If I disconnect the battery do I still need to worry about anything touching while I disconnect all the ECM wires?
Will I notice anything (other than the light issue) once I disconnect the remaining ecm wires? Will it run any different? Given that I have an aftermarket Holley carb and no hooked up emission stuff is the ECM even doing anything at the moment? I wanted to replace the dash bulbs anyways so if it means pulling the one out I me not too concerned about it. Lastly, do I need any of the exemption stuff for my AC? As you suggested, I do plan to put the AC system back.
If you disconnect the batt, there will be no power to anything, so no risk of sparks or damage or whatever.
No there should be no significant consequences of removing the ECM since you have a 5-spd. If you had an auto, it would be responsible for locking up the converter, but you don't have that issue. The ECM controlled only the carb, distributor, EGR, AIR, and Check Engine light, in your car; with the possible exception of the speedo (I am more familiar with the Camaro, not positive when or in what models they changed to the electronic speedo in the Bird, I just know it was earlier than Camaro). It has no connection to the AC at all. The entire HVAC harness is its own unit, installed as part of whichever system the car got, on the final assembly line.
The only other thing it might still be doing, is controlling the ignition timing. You need a distributor with vacuum advance if you don't already have one. Otherwise it will stay at the base (static) timing at all times with no dynamic advance whatsoever, and will run real lazy, have even less power, suck down fuel mercilessly, and overheat.
okay thanks - I will do as you suggested and trace every wire from the ECM so I know what it was still hooked up to - based on the things you mentioned, I cannot believe it is hooked up doing anything. I am pretty sure I have an aftermarket distributor installed - it has a hose that connects from from a round silver piece on the out side of the distributor to a port on the carb - watching the holley videos, the port it is connected to is supposed to be for a vacuum advance hose so I am guessing that is what it is?
I did some work with the fuel hose on the weekend (as thinking there was an akward bend after the t-split - it's dual feed so there is a split in the fuel hose) - seem to run a little better and accelerates really nice. idle is pretty solid just below 1 once it warms up a little.
09-01-2017, 12:14 PM
It's just electricity. Probably the simplest subsystem of a car, with the possible exception of the cooling system. 