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Need help identifying what this does. Was told it has something to do with A/C but my car doesn't have A/C. Can I remove it with out any negative effects? '72 base motor, Rochester Quadrajet.
It is used for setting the idle speed not the carburetor screw.
Do you have the emissions sticker, drivers side near the hood catch?
Below is a link with the label giving the directions on how to set idle using the solenoid. https://www.ebay.com/i/361955690142?...SABEgJ8LPD_BwE
It's to prevent dieseling or run on. With the engine on and the solenoid energized it should hold idle at 800 or 850 if you choose in a 4 speed then when you turn off the car the idle should drop far enough to kill the engine. I think the idle screw should be set around 500 rpm-just enough to keep the car running if you start it and don't hit the gas- if you use the solenoid.
It's called an "idle stop solenoid" or "anti-Diesel solenoid". As others said, it sets the normal idle speed. It is energized (extended) with the ignition at "on". When the ignition is turned off, it retracts and lowers the idle speed to the point that the engine can't Diesel (run on by igniting the fuel via compression alone). I believe these were only used with high compression engines burning leaded ("ethyl") fuel. "Ethyl" was the octane boosting lead additive (tetraethyllead) produced by the Ethyl Corporation.
It's the same solenoid used for some A/C systems but in that case the purpose is to bump up the idle speed with the A/C is turned on. This allows a very low base idle speed on A/C equipped cars.
Thank you for all the responses, sounds as though it's a dual purpose solenoid.
Nope. On a '72 it's a single purpose anti-diesel solenoid, emission related. Present on all engines, AC or not. Might have had an AC function on some other years, but not '72. The vac advance uses ported vac on these cars, it reduces idle emissions but severely heats up the engine and pistons at idle, to the point where they will easily "self-ignite" or run-on, hence the need to slam the throttle shut once you turn off the key. The system never really worked that well.
If you are keeping the car 100% stock NCRS, then keep it working. If you have dieseling problems, fix it. If you have ported vac advance, keep it.
Otherwise the best thing you could do would be to use manifold vacuum for distributor advance, and then you won't need this, you could leave it or un-plug it. Your car will run better and cooler and it'll thank you!
To see if you have ported or manifold vac advance follow the rubber hose from the distrib and see where it leads.....
Last edited by leigh1322; Dec 2, 2019 at 06:52 PM.
Carburetor part I.D.
