1981 computer help
Thread Starter
Pro
Joined: Aug 2007
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From: Mississippi
Larryg-What book are you using to show me these pictures?
7T1vette- Where do you get the service manual?
Today I installled the new battery and it did not solve my WOT throttle problem. This morning after the car had been sitting all night it ran great at WOT with no shut down. Later in the day while cruising for about 30 minutes I tried WOT again and it starts shutting down again. It seems after you drive it a while is when the problem starts. It gets worse the more you drive and you dont even have to be at WOT to start having problems with the shut down. Dont believe it to be the fuel pump because it dosent do it first thing. It may be Vapor lock? Or the coil is getting warm and causing problems. I need to solve this issue before I go back to the ECM issue although I will check the CEL bulb tomorrow. Again thanks for the help. Mike
7T1vette- Where do you get the service manual?
Today I installled the new battery and it did not solve my WOT throttle problem. This morning after the car had been sitting all night it ran great at WOT with no shut down. Later in the day while cruising for about 30 minutes I tried WOT again and it starts shutting down again. It seems after you drive it a while is when the problem starts. It gets worse the more you drive and you dont even have to be at WOT to start having problems with the shut down. Dont believe it to be the fuel pump because it dosent do it first thing. It may be Vapor lock? Or the coil is getting warm and causing problems. I need to solve this issue before I go back to the ECM issue although I will check the CEL bulb tomorrow. Again thanks for the help. Mike
Team Owner
Joined: Jan 2006
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From: Crossville TN
Most of the Corvette aftermarket places sell the C3 Service Manuals. Or you can check on eBay or Amazon to see if there are any for sale there. I believe that GM Restoration Parts may sell them also; check on their website.
Le Mans Master
Joined: Oct 2002
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From: Las Vegas - Just stop perpetuating myths please.
Try the ECM trouble codes?
There are some DTC trouble codes for '81 ECM though not many. U need to short the "B" pin to the "A" pin on the ALCL connector under the dash and interpret the Service Engine light flashing codes. Take a look at this w/s:http://www.neilkline.com/Tech%20Tips/obdcodes.htm.
Let us know what u read.
IMHO it sounds like your secondary circuit is having problems. Even in an electronic Qjet the secondaries still are controlled manually by the air valve.
Good luck,
cardo0
Let us know what u read.
IMHO it sounds like your secondary circuit is having problems. Even in an electronic Qjet the secondaries still are controlled manually by the air valve.
Good luck,
cardo0
Drifting
Joined: Apr 2008
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From: Antioch IL
[QUOTE=mkh;1583322853]Larryg-What book are you using to show me these pictures?
sorry for not responding earlier but I did not have a chance to go on the forum this weekend. The book I am using for the diagrams is the service manual. You can get this via the supporting vendors.
Larry
sorry for not responding earlier but I did not have a chance to go on the forum this weekend. The book I am using for the diagrams is the service manual. You can get this via the supporting vendors.
Larry
Thread Starter
Pro
Joined: Aug 2007
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From: Mississippi
Ok I had a dead cell in the battery and have now replaced battery. Still have the fuel issue and will replace the fuel pump Wednesday or Thursday night and hope this cures the problem. I drove it today and held the pedal to the floor and when it shut down I never released the pedal from the floor and the car went dead. I then held the pedal to the floor and when it shut down I let off the pedal and began to feather the pedal and it caught back up. Hope its the fuel pump.
I was able to pull the center dash today and replaced the seatbelt warning and the cel bulbs. The seat belt warning light now works but still cant get the cel bulb to light. I even switched the seat belt warning bulb and the Ccel bulb just to eliminate a bad bulb.
I used a test light to either side of the cel bulb when it was installed and the test light lights up. I dont see how I can have power to both sides of the cel bulb but the cel bulb is not lit? I also had power to both sides of the printed circuit where the bulb installs but no cel light?
Thanks, Mike
I
I was able to pull the center dash today and replaced the seatbelt warning and the cel bulbs. The seat belt warning light now works but still cant get the cel bulb to light. I even switched the seat belt warning bulb and the Ccel bulb just to eliminate a bad bulb.
I used a test light to either side of the cel bulb when it was installed and the test light lights up. I dont see how I can have power to both sides of the cel bulb but the cel bulb is not lit? I also had power to both sides of the printed circuit where the bulb installs but no cel light?
Thanks, Mike
I
Thread Starter
Pro
Joined: Aug 2007
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From: Mississippi
Larrg, On the CEL light inoperative page you showed me is reads about terminal G, U and C. When I pull the ashtray I only have 5 terminals? Also can you explain what " Check voltage from ECM term G to ground with ignition on" means? Are the terminals on the computer or the test port under the ashtray?
Thanks for all the help.
Thanks for all the help.
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Thread Starter
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From: Mississippi
Update- I installed a new fuel pump today. Not fun, had to pull the air compressor and recharge the freon. I did not help at all. Today I pulled the tank and the Sock was colapsed. I removed it and now the car runs great with no fuel issues.
Back to the CEL issues-I used a test light to either side of the cel bulb when it was installed and the test light lights up. I dont see how I can have power to both sides of the cel bulb but the cel bulb is not lit? I also had power to both sides of the printed circuit where the bulb installs but no cel light? Any ideas why it will not come on? Making progress but slow.
Thanks, Mike
Back to the CEL issues-I used a test light to either side of the cel bulb when it was installed and the test light lights up. I dont see how I can have power to both sides of the cel bulb but the cel bulb is not lit? I also had power to both sides of the printed circuit where the bulb installs but no cel light? Any ideas why it will not come on? Making progress but slow.
Thanks, Mike
Le Mans Master
Joined: Jan 2006
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From: Boca Raton Florida
Update- I installed a new fuel pump today. Not fun, had to pull the air compressor and recharge the freon. I did not help at all. Today I pulled the tank and the Sock was colapsed. I removed it and now the car runs great with no fuel issues.
Back to the CEL issues-I used a test light to either side of the cel bulb when it was installed and the test light lights up. I dont see how I can have power to both sides of the cel bulb but the cel bulb is not lit? I also had power to both sides of the printed circuit where the bulb installs but no cel light? Any ideas why it will not come on? Making progress but slow.
Thanks, Mike
Back to the CEL issues-I used a test light to either side of the cel bulb when it was installed and the test light lights up. I dont see how I can have power to both sides of the cel bulb but the cel bulb is not lit? I also had power to both sides of the printed circuit where the bulb installs but no cel light? Any ideas why it will not come on? Making progress but slow.
Thanks, Mike
The circuit is either happy, or whatever alarm condition there is is not reaching the lamp circuit.
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From: Mississippi
Hi Thanks for keeping this thread alive. I spoke about the blue splice connecting two of the four pin wires together in a earlier post with this thread. Not sure what it was doing there it just hooked 2 of the original wires together that comes out of the distributor. I have removed this splice.
Do I understand you right "If you have power (12v) on both sides of the bulb there is no difference in potential, therefore no current, therefore no light.
The circuit is either happy, or whatever alarm condition there is is not reaching the lamp circuit" Are you saying the CEL light board is working correctly? Meaning I dont have a problem with the board and I can continue to figure out why I never have a CEL on. Thanks, Mike
Do I understand you right "If you have power (12v) on both sides of the bulb there is no difference in potential, therefore no current, therefore no light.
The circuit is either happy, or whatever alarm condition there is is not reaching the lamp circuit" Are you saying the CEL light board is working correctly? Meaning I dont have a problem with the board and I can continue to figure out why I never have a CEL on. Thanks, Mike
Le Mans Master
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From: Boca Raton Florida
Thats more or less what I am saying.
Check out the schematic. There should be 12v on the top of the bulb with the key on, for the light to come on, you have to have a ground onthe other side of the element, that makes the current flow and the light light.
The ground for the lamp comes from the CCC connector C434 pin 419, thats a brown and white wire. Same wire is on the diag connector, ground it and the light should come on if the path is good. If you verify the path for the lamp is good and your still not getting codes your CCC is probably bad.
Check out the schematic. There should be 12v on the top of the bulb with the key on, for the light to come on, you have to have a ground onthe other side of the element, that makes the current flow and the light light.
The ground for the lamp comes from the CCC connector C434 pin 419, thats a brown and white wire. Same wire is on the diag connector, ground it and the light should come on if the path is good. If you verify the path for the lamp is good and your still not getting codes your CCC is probably bad.
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From: Mississippi
Sixfooter, thanks for the continuing help. I have service manual that should be here any day. You quoted "Same wire is on the diag connector, ground it and the light should come on if the path is good"
What is the diag connector? I just need to see the CEL come on before I purchase a new CCC just to make sure it works. Mike
What is the diag connector? I just need to see the CEL come on before I purchase a new CCC just to make sure it works. Mike
Team Owner
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From: Southern Cal Ca
St. Jude Donor '22
Sixfooter, thanks for the continuing help. I have service manual that should be here any day. You quoted "Same wire is on the diag connector, ground it and the light should come on if the path is good"
What is the diag connector? I just need to see the CEL come on before I purchase a new CCC just to make sure it works. Mike
What is the diag connector? I just need to see the CEL come on before I purchase a new CCC just to make sure it works. Mike
(there is a cut out between the two poles) puts the system in diag ode.
first should see, 1 blink then 2 blinks (repeats three times) then
any blimks after are codes. ext, 2 blinks then 3 blinks (3 times) is
code 23.
light should come on when key is in run.
pole #5 can be used as a ground to test the light
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From: Mississippi
Thanks, I have tried jumping the test connectors but no luck getting the CEL to light. There are 5 connectors under the ashtray. The first 2 have a cutout between them. These are on the drivers side on my car.
Mike
Mike
Team Owner
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From: Southern Cal Ca
St. Jude Donor '22
until the light comes on with the key in run, engine stopped,
there is nothing the connector can do but supply a handy ground.
when you get the manual, there are diagrams of the circuits.
from a quick look at the pictures, the carb solenoid is not stock,
4pin dist connector jumped. other wires not looking right.
did the other owner tell you anything?
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From: Mississippi
Update: I went to a car show saturday and someone just had to have it. Thanks for all the help as I was able to fix everything except the computer issue. I had just received the service manual and was going to replace the computer this week. Well I guess I can start looking for another to fill the garage space. Thanks again for the help. Mike