Idle Stop Solenoid? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1972Blaze · 10-18-2013, 06:13 PM

What was the purpose of the idle stop solenoid for my 1972? Was it used specifically on vehicles equipped a certain way or were they put on all trucks? My truck has A/C and it will not stay running without adjusting the idle way up when the A/C is on. I had an Edelbrock carb (no idle up that I can identify) and replaced it with an original Quadrajet, but it had no idle up solenoid. If I put one on and it works properly will it idle the engine up when the A/C is on? What causes the solenoid to engage? What does the wire to the solenoid look like? I have a green with white stripe wire loose that I suspect may be the right wire. Any help is appreciated.

68gmsee · 10-18-2013, 07:46 PM

There's basically two purposes - idle up and idle stop.

I can't remember if our trucks came with the idle up for A/C but the solenoid kicks in when the A/C compressor is engaged.

The idle stop engaged while engine was running to keep the idle up and disengaged when ignition key turned off to close the butterflies completely. Stopped engines from dieseling.

1972Blaze · 10-19-2013, 09:57 AM

Good info, thanks. Can anyone give me info on the original wire that connected to it?

Carl Spangler · 10-19-2013, 10:37 AM

Thanks for posting this question. My 71 has an idle stop solenoid but the PO has it wired up to a manual switch for when running aux devices. Normally the idle is "low" (sol switch off) and the engine does diesel a bit when shut off. It almost looks like I need to rewire that sol so that it goes ON when the engine is ON. ???

regards
JohnG

68gmsee · 10-19-2013, 11:58 AM

As I mentioned above, I'm not sure our year trucks came with the idle up/stop solenoid but if it's an idle up solenoid it could be wired to 12vdc ignition on wire. If I remember right, adjust the idle while engine is running and solenoid engaged. If it's for A/C you could wire it in the with the A/C switch 12vdc and adjust with compressor engaged. If you post in the electrical section, someone may be able to give you more info.

As for the dieseling, I'd put a couple of cans of Sea Foam or other fuel tank additive to clean the carbon out. My old 68 took three tanks full with the additive to clean the carbon out. Haven't had any more dieseling problems for 2-3 years.

10-18-2013, 06:13 PM	#1
1972Blaze Registered User Join Date: May 2013 Location: Covington, Louisiana Posts: 243	Idle Stop Solenoid? What was the purpose of the idle stop solenoid for my 1972? Was it used specifically on vehicles equipped a certain way or were they put on all trucks? My truck has A/C and it will not stay running without adjusting the idle way up when the A/C is on. I had an Edelbrock carb (no idle up that I can identify) and replaced it with an original Quadrajet, but it had no idle up solenoid. If I put one on and it works properly will it idle the engine up when the A/C is on? What causes the solenoid to engage? What does the wire to the solenoid look like? I have a green with white stripe wire loose that I suspect may be the right wire. Any help is appreciated. __________________ 1972 K5 Blazer Cheyenne 1966 L72 Corvette Convertible 2016 GMC Yukon Denali

10-18-2013, 07:46 PM	#2
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Idle Stop Solenoid? There's basically two purposes - idle up and idle stop. I can't remember if our trucks came with the idle up for A/C but the solenoid kicks in when the A/C compressor is engaged. The idle stop engaged while engine was running to keep the idle up and disengaged when ignition key turned off to close the butterflies completely. Stopped engines from dieseling. __________________ 68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive...

10-19-2013, 09:57 AM	#3
1972Blaze Registered User Join Date: May 2013 Location: Covington, Louisiana Posts: 243	Re: Idle Stop Solenoid? Good info, thanks. Can anyone give me info on the original wire that connected to it? __________________ 1972 K5 Blazer Cheyenne 1966 L72 Corvette Convertible 2016 GMC Yukon Denali

10-19-2013, 10:37 AM	#4
Carl Spangler Registered User Join Date: Oct 2013 Location: Central Coast Ca. Posts: 417	Re: Idle Stop Solenoid? Thanks for posting this question. My 71 has an idle stop solenoid but the PO has it wired up to a manual switch for when running aux devices. Normally the idle is "low" (sol switch off) and the engine does diesel a bit when shut off. It almost looks like I need to rewire that sol so that it goes ON when the engine is ON. ??? regards JohnG

10-19-2013, 11:58 AM	#5
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Idle Stop Solenoid? As I mentioned above, I'm not sure our year trucks came with the idle up/stop solenoid but if it's an idle up solenoid it could be wired to 12vdc ignition on wire. If I remember right, adjust the idle while engine is running and solenoid engaged. If it's for A/C you could wire it in the with the A/C switch 12vdc and adjust with compressor engaged. If you post in the electrical section, someone may be able to give you more info. As for the dieseling, I'd put a couple of cans of Sea Foam or other fuel tank additive to clean the carbon out. My old 68 took three tanks full with the additive to clean the carbon out. Haven't had any more dieseling problems for 2-3 years. __________________ 68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive...



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