Idle stop solenoid
Thread Starter
Intermediate
Joined: Sep 2009
Posts: 26
Likes: 0
From: Wichita KS
Idle stop solenoid
74 big block 454 with stock Quadrajet. Can someone tell me the function of the idle stop solenoid mounted on the throttle side front corner of the carb? Also, how to correctly test the solenoid for functionality?
Racer
Joined: Jul 2009
Posts: 336
Likes: 1
From: Asheville N.C.
The wire from the solenoid runs to the a/c compressor, when a/c is turned on while idleing your rpm's will drop, with the breather off (better to see) when you increase the rpm's you will notice the solenoid piston extend outward to hold the linkage at a higher rpm, hope this helps.
Ed
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
The '74 version may be different from my '71 (w/ac), but the idle stop solenoid is NOT used to prevent dieseling on mine. The idle stop solenoid is used to reduce idle speed when in upper grear ranges at closed throttle and to set a curb idle speed. The anti-dieseling function (on A/C cars) is a 3-second timer which sends power to the A/C clutch when the engine is turned off. The extra load from the compressor prevents engine run-on.
Melting Slicks
Joined: Mar 2008
Posts: 2,023
Likes: 6
From: Austin Tx
The solenoid on the carb that when energized bumps the accerator lever, is commonly called the idle stop solenoid.
In early years this solenoid is energized whenever the ignition is on. It is deenergized when the ignition is turned off, and is used to stop engine desieling.
In later years, it was tied to the A/C system, and was also used to bump up the idle speed when the A/C compressor was running - I believe this was to help with engine cooling when idleing.
In 71, there was a 1 year only CEC system. The CEC (Combined Emissions Control system) solenoid replaced both the TCS solenoid (used in 70 and 72), and the idle stop solenoid. More info can be found here - start on page 5. http://ncrsrmc.org/Downloads/Mar-2006-Newsletter.pdf
To know exactly how it was used in 74, I believe you will need to either look in a 74 service manual, or find out from someone with a correctly functioning 74.
In early years this solenoid is energized whenever the ignition is on. It is deenergized when the ignition is turned off, and is used to stop engine desieling.
In later years, it was tied to the A/C system, and was also used to bump up the idle speed when the A/C compressor was running - I believe this was to help with engine cooling when idleing.
In 71, there was a 1 year only CEC system. The CEC (Combined Emissions Control system) solenoid replaced both the TCS solenoid (used in 70 and 72), and the idle stop solenoid. More info can be found here - start on page 5. http://ncrsrmc.org/Downloads/Mar-2006-Newsletter.pdf
To know exactly how it was used in 74, I believe you will need to either look in a 74 service manual, or find out from someone with a correctly functioning 74.
Thanks
Thread Starter
Intermediate
Joined: Sep 2009
Posts: 26
Likes: 0
From: Wichita KS
Thanks all for your input! It appears to be setting idle stop only and closing the butterfly when engine is off (to prevent dieseling). I placed a 12v jumper on it tonight and the plunger reacted immediately just as it should. (One less part to replace 
)
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