1971 350/270 Auto Quadrajet The CEC Solenoid engauges the throttle lever on the carb for just a couple seconds upon start up. Is this correct?


I also just noticed that it extends for just a couple of seconds when in drive and stays extended when in reverse. It does not extend when air is turned on.

[Modified by Tom Johnson, 12:30 PM 2/27/2004]


[Modified by Tom Johnson, 12:50 PM 2/27/2004]

 

When the ignition key is "on", the solenoid is energized, thereby opening the throttle plate to a position that determines idle speed. When the key is turned "off", the solenoid is de-energized. This allows the throttle plate to close completely, which prevents air from entering the engine. This lack of air prevents the car from dieseling.

It is easy to check the idle stop solenoid for action because it has a visible idle lever positioner. This positioner extends to set the throttle to idle speed as soon as the key is turned to the "on" position. It will also retract when the key is turned to the "off" position.If an engine starts but won't idle, this solenoid is the first device to check for action. A visual check is all it takes. The solenoid must be replaced if it is defective.

from: http://www.napaechlin.com/cpc7f.htm

 

To my understanding the CEC Solenoid is unique to the 71 which is different than a TCS.


[Modified by Tom Johnson, 12:30 PM 2/27/2004]

 

My bad!

I found this:
On some Quadrajet applications, a carburetor mounted Combination Emission Control (C.E.C.) valve is added to help reduce exhaust emissions (Figure 25). A vacuum tube in the float bowl is connected by hose to the C.E.C. valve which, when energized through the transmission, controls distributor vacuum spark advance by providing spark vacuum advance during transmission high-gear operation (and in reverse on turbo-hydramatic transmission applications) and, when de-energized, retarded spark timing during operation of the transmission in lower gears and at idle.

The C.E.C. valve, when energized through the transmission, also acts as a throttle stop by increasing engine idle speed during high-gear operation (and in reverse on turbohydramatic transmission applications) to add more air as an aid in controlling over-run hydrocarbons (unburned fuel) during deceleration. Normal idle speed setting is made with the idle stop screw. Idle speed settings should be made following vehicle manufacturer's specification (noted on the decal in the engine compartment).

The C.E.C. valve may be identified from the idle stop solenoid by two vacuum tubes for distributor vacuum advance, located at the end of the valve, and by the following precautionary label affixed to the valve:

"CAUTION: Never use to set idle. See Service Manual for adjustments. "

Here: http://www.tocmp.com/manuals/Carbs/R...73_4M_0017.htm

Sounds like it engages the throttle lever in high gear.

 

Also found this:

GM's Combined Emission Control (CEC) system is an adaptation of this principle. The solenoid valve's plunger acts as an auxiliary throttle stop. During high gear deceleration, it holds the throttle open a predetermined amount, which leans down the mixture in that normally rich, high-vacuum mode.

 

It is supposed to engage for approx. 15 seconds upon start-up. It will stay engaged until operating temperature reaches approx. 120 degrees and engage if your temperature exceeds approx. 230 degrees (if your temp. sender in the right cylinder head is functioning properly).
Along with anti-dieseling, the main purpose was to eliminate vaccuum advance to the distributor except when engaged, thus improving emissions.

 

Great info guys. Thank you very much. I gonna order a new water tempeture sending unit for the CEC.