1981 Running Problems
Drifting
Joined: Aug 2019
Posts: 1,339
Likes: 225
Don't be too fast to blame the ecm. If you unplug the mixture control solenoid, the ecm is out of the fuel control picture, the metering rods will pull out and the carb will run rich at idle. I would think that the car being 45 years old that the ethanol in the fuel has affected the check valve in the pump. A good fuel pump should generate 5-7" of vacuum if you have the ability to test it. You can also check the pump by disconnecting the fuel inlet line at the carb, and then crank it. Use a towel. You should see plenty of fuel coming out at cranking. If not, then the pump is suspect.
Last edited by Mrvettenick; Jun 4, 2026 at 02:31 PM.
Drifting
Joined: Aug 2019
Posts: 1,339
Likes: 225
I set the timing and used a dwell meter to set the idle mixture screws when the car was running about a month ago. There is clearly something wrong with the carb. I could not get the dwell to move off of about 20. meaning it would not move at all no matter what i did to the mixture screws or the air bleed. At that time i just set the idle mixture screws and the air bleed to the startign settings and it ran alright.
Sadly, the car would not run again today. I am working with Quadrajet power to get the rebuilt parts and ordering a new fuel pump. we will see where it goes.
Sadly, the car would not run again today. I am working with Quadrajet power to get the rebuilt parts and ordering a new fuel pump. we will see where it goes.
Thread Starter
Heel & Toe
Joined: Nov 2025
Posts: 24
Likes: 2
From: Boston
Don't be too fast to blame the ecm. If you unplug the mixture control solenoid, the ecm is out of the fuel control picture, the metering rods will pull out and the carb will run rich at idle. I would think that the car being 45 years old that the ethanol in the fuel has affected the check valve in the pump. A good fuel pump should generate 5-7" of vacuum if you have the ability to test it. You can also check the pump by disconnecting the fuel inlet line at the carb, and then crank it. Use a towel. You should see plenty of fuel coming out at cranking. If not, then the pump is suspect.
Thread Starter
Heel & Toe
Joined: Nov 2025
Posts: 24
Likes: 2
From: Boston
Don't be too fast to blame the ecm. If you unplug the mixture control solenoid, the ecm is out of the fuel control picture, the metering rods will pull out and the carb will run rich at idle. I would think that the car being 45 years old that the ethanol in the fuel has affected the check valve in the pump. A good fuel pump should generate 5-7" of vacuum if you have the ability to test it. You can also check the pump by disconnecting the fuel inlet line at the carb, and then crank it. Use a towel. You should see plenty of fuel coming out at cranking. If not, then the pump is suspect.
Thread Starter
Heel & Toe
Joined: Nov 2025
Posts: 24
Likes: 2
From: Boston
If the car is running lean, the ecm will open the jets/rods as much as possible, which is why the ecm is keeping the dwell at 20 degrees. Just curious what your oxygen sensor is reading. I'll bet it's constantly below .450mv. The computer sees that and tries to richen the mixture to address that, but it's limited with what it can do.
