1981 Computer

[Richard Cooper]

I am still having trouble with my mixing control valve not working. If I hook up a seperate source of power I can get the valve in the carb to fire every time I ground it, so I think the valve is good. I do not have any brakes in any of the wires going to the computer from the control valve, so I am thinking that the computer may be bad. Does anyone know of any way to test the computer? Thanks for any help and have a good day.

 

[81vetter]

Richard, don't know specifically about your mixing valve problem but just went through some computer problems of my own.
Under the ashtray in your console is a five pin connector...this is the connector to the ecm ( which is in your battery compartment, forward of the battery).
Jump the pin with a notch in the plastic to the one next to it and watch your computer light on the dash. Count the flashes, its giving you a code. If you have a problem (that the computer can identify) it will show up here.
There is a way to do it with the key on or off.
Best bet is get the GM shop manual for the 81 vette...best $80 bucks you'll ever spend...its all spelled out in there in black and white with the proper procedure, codes, meanings etc....
Let me know if I can help you out any further.
Darryl

 

[Richard Cooper]

Thanks Darryl, I am getting a code 23 from my computer. Its a open or grounded M/C solenoid. I know the mixing control valve is good because if I put power to it from another battery I can make the valve click every time I hit ground. I also know that there are no brakes in the wiring because I have checked them from the valve to the computer and they are good. Now, I'm out of ideas and driving with the CHECK ENGINE light on all the time.
Thanks again.

 

[81vetter]

do u have a shop manual...I can try emailing you the page for troubleshooting code 23.

 

[Richard Cooper]

Yes, I have the 81 repair manual. I am going to sears today to buy a dwell meter. If this rain ever stops I will get out to my shed to do some work on the vette. I am now working the third shift (11PM till 7AM) at work until the plant closes for good on july 25th so I have time during the day to get stuff done.
Thanks again and if you ever need any help, I have replaced my body mounts and valve stem seals, so I can help you with these.

 

[Vader]

Before you set the M.C.S., make sure the engine is at temperature and the idle RPM is correct (TPS voltage correct as well).

What color wires are on the connector for your MCS?

 

[Richard Cooper]

Vader, the mixing control solenoid has two wires, one is green and the other is pink.

 

[Vader]

RC,

Thanks for the help. My manual showed a Lt. Blue and Pink/Black wire. The pink has just a faint black tracer. The "gree" is what confused me, since the manual states "blue". Sure engough, mine looks green. I traced it back farther into the protecive accordian tube, and, sure enough, it looks light blue. I guess engine heat and years have altered the colors.

Next question - There is also a two-wire WeatherPal that is the same as the MC solenoid connector, but has a gray body. It has a brown and darker blue wire in it. Any idea where this goes? The Air Injection divert/port solenoid, perhaps?

As for your MC, the solenoid is probably O.K. If the ECM has detected a rich or lean condition, the solenoid may not duty cycle at all, but remain static in either an energized or de-energized state.

Have you checked the O² sensor signal? Is the CTS reporting correctly to the ECM?

 

[Richard Cooper]

vader,
It looks like that brown and dark blue plug go to the air pump. My air pump is removed but the plug that you mention is sitting right there. Let me know if this has helped you. If not then I can get the repair manual and see if I can find the exact wire you are talking about.

 

[Vader]

RC,

Thanks again. Yes, those are the same colors. I found thst connector plugged into the MCS, hence teh orignial question. No wonder the ECM wasn't controlling mixture. I've found a few more wires hacked off and restored most of the engine harness today. I'm actually getting EST advance at the distributor now. Some people shouldn't own anything but a bicycle. Man, was this thing hacked.

Next, the audio system and alarm system that's been hacked out.

Thanks again.

 

[Richard Cooper]

Vader,
Do you have the 1981 repair manual? If not and you need anything from it just let me know and I will have copies made and send it to you. Good luck.