Carb Idle Speed Solenoid
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Joined: Dec 2020
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From: Babson Park Florida
Carb Idle Speed Solenoid
Hope everyone is having a relaxing Sunday.
Looking for guidance for my 71 C3. When the AC is running the engine bogs and stalls at idle speed. Given we live in central Florida AC is a must and yes, I could put my foot on the gas but it’s a nice car and I want it to work as it should let alone the snide comments from the wife when it stalls (I know ya’ll not marriage consolers)!
My understanding is the carb idle speed solenoid plunger extends to adjust the accelerator linkage increasing the idle speed when the AC is on to prevent the engine from stalling. It looked to be dead so I replaced it with the proper Delco Solenoid #1114444 for my 350, checked vacuum hoses, cleaned and checked power connections at the solenoid and AC compressor and adjusted the push rod to the back side of the accelerator linkage.
Well, same thing, the solenoid plunger doesn’t extend and make contact with the linkage, the engine stalls and here come the wife remarks!
Alan
Looking for guidance for my 71 C3. When the AC is running the engine bogs and stalls at idle speed. Given we live in central Florida AC is a must and yes, I could put my foot on the gas but it’s a nice car and I want it to work as it should let alone the snide comments from the wife when it stalls (I know ya’ll not marriage consolers)!
My understanding is the carb idle speed solenoid plunger extends to adjust the accelerator linkage increasing the idle speed when the AC is on to prevent the engine from stalling. It looked to be dead so I replaced it with the proper Delco Solenoid #1114444 for my 350, checked vacuum hoses, cleaned and checked power connections at the solenoid and AC compressor and adjusted the push rod to the back side of the accelerator linkage.
Well, same thing, the solenoid plunger doesn’t extend and make contact with the linkage, the engine stalls and here come the wife remarks!
Alan
Race Director
Joined: Apr 2011
Posts: 11,183
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From: North of Toronto - Ontario
The idle stop solenoid isn't there to compensate for the AC, it was just to drop the engine rpm way too low so it quit instead of "dieseling". (AC compensation did come along later but not in the early 70s)
The solenoid should shoot out when the key is turned on (run position) They usually don't seem to have enough power to actually push the throttle on the carb, but enough to hold it once it is out, the gas pedal was pressed and the solenoid could extend all the way
The idle speed was set by turning the bolt on the solenoid out, the idle screw on the carb body was turned way in and not really used. 71 used the carb screw for curb idle
Anyway, your solenoid was also part of that CEC system for 71 which was unique to that year as it also controlled the vacuum so it wasn't used to set idle, I believe it was used to keep the engine RPM up higher at idle until the car warmed up (and prevented the vacuum advance from working) to keep the gar running hot to burn more emissions until it actually reached proper temp and then it dropped off out of the way and allowed vacuum to the advance system
One way on another, it should extend when the key was turned on, AC shouldn't matter at all.
Check for power going to it with the key on
M
The solenoid should shoot out when the key is turned on (run position) They usually don't seem to have enough power to actually push the throttle on the carb, but enough to hold it once it is out, the gas pedal was pressed and the solenoid could extend all the way
Anyway, your solenoid was also part of that CEC system for 71 which was unique to that year as it also controlled the vacuum so it wasn't used to set idle, I believe it was used to keep the engine RPM up higher at idle until the car warmed up (and prevented the vacuum advance from working) to keep the gar running hot to burn more emissions until it actually reached proper temp and then it dropped off out of the way and allowed vacuum to the advance system
One way on another, it should extend when the key was turned on, AC shouldn't matter at all.
Check for power going to it with the key on
M
Last edited by Mooser; Apr 28, 2024 at 04:01 PM.
Race Director
Joined: Apr 2011
Posts: 11,183
Likes: 3,334
From: North of Toronto - Ontario
Le Mans Master
Joined: Mar 2001
Posts: 5,738
Likes: 644
From: Lincoln, CA
I have a 69 with Vintage Air and also found the idle would drop too low. I added the solenoid and wired it to a switch inside the cab.
My idle is 850 RPM and it jumps to 1000 RPM with out the AC on. Works great.
My idle is 850 RPM and it jumps to 1000 RPM with out the AC on. Works great.
Race Director
Joined: Apr 2011
Posts: 11,183
Likes: 3,334
From: North of Toronto - Ontario
The later cars had it wired like that, not sure what year it changed, probably when the gas grades were so crappy the cars could barely burn it when running, forget about dieseling...
M
Drifting
Joined: Oct 2020
Posts: 1,566
Likes: 573
From: Wisconsin
I did this exact thing on my ‘71, though the bracket and solenoid were missing. I couldn’t find a bracket that cost less than my mortgage, so I ended up making one. An eBay solenoid and a switch got it done. I find I don’t need it all the time, so I just switch it on when I do need it.
