Idle stop solenoid

[SRU1436]

I have an idle stop solenoid on my 72 c10. It’s a factory 350, no ac, California truck. I’m not sure if it’s needed, there re no other emissions things on the engine. I’m rebuilding the carb, and was wondering if it’s needed. I guess it doesn’t hurt to put it back on, but is it necessary? Thanks, Matt.

[Hidesertchevy]

It’s for an a/c system to bump up idle when compressor cycles on. You can remove it if you don’t have a/c.

[lil hoodlum]

Originally Posted by hidesertchevy

it’s for an a/c system to bump up idle when compressor cycles on. You can remove it if you don’t have a/c.

x2

[Steeveedee]

Some engines got it as an anti-dieseling solenoid- energized when the ignition is on. When the power is off, the throttle blades completely close and engine after-run is eliminated.

[Rich72C10]

Funny, I just posted about this in another thread. In our trucks it isn't for the A/C but for anti-dieseling, just as Steven reports in his reply.

That isn't to say in later model cars/tracks this solution was switched to bumping up the idle when the A/C kicked on. As far as I know '72 C10s & before the solenoid wasn't ever from the factory for the A/C / Idle bump up.

My thread on this same subject from ~5 years ago.
https://67-72chevytrucks.com/vboard/...d.php?t=812766

[SRU1436]

Thanks for the reply’s, I’m going to do a function check to see if it even works.

[Stanco]

It's actually part of the TCS system. In an effort to reduce emissions They increased the mechanical advance in the distributor while reducing the initial advance. The TCS system shut down the vacuum advance until the transmission was in high gear. With the reduced initial advance they had to open the throttle more to get it to idle. This caused a dieseling problem on shut down hence the solenoid.

I recurved my distributor with 12° mechanical (24° at the crankshaft) + 12° initial for 36° total advance all in at 3200 RPM. I'm also running full manifold vacuum advance.

I removed the TCS system including all the wiring and the idle stop solenoid. I used the 12 gauge pink idle stop solenoid wire to power the Petronix module I installed in the distributor. This large pink wire is controlled by the ignition switch and was perfect to power the Petronix module. The truck idles and runs much better with this tune.

[SRU1436]

Originally Posted by Stanco

It's actually part of the TCS system. In an effort to reduce emissions They increased the mechanical advance in the distributor while reducing the initial advance. The TCS system shut down the vacuum advance until the transmission was in high gear. With the reduced initial advance they had to open the throttle more to get it to idle. This caused a dieseling problem on shut down hence the solenoid.

I recurved my distributor with 12° mechanical (24° at the crankshaft) + 12° initial for 36° total advance all in at 3200 RPM. I'm also running full manifold vacuum advance.

I removed the TCS system including all the wiring and the idle stop solenoid. I used the 12 gauge pink idle stop solenoid wire to power the Petronix module I installed in the distributor. This large pink wire is controlled by the ignition switch and was perfect to power the Petronix module. The truck idles and runs much better with this tune.

Thanks for the info.

[Steeveedee]

Originally Posted by Stanco

It's actually part of the TCS system. In an effort to reduce emissions They increased the mechanical advance in the distributor while reducing the initial advance. The TCS system shut down the vacuum advance until the transmission was in high gear. With the reduced initial advance they had to open the throttle more to get it to idle. This caused a dieseling problem on shut down hence the solenoid.

I recurved my distributor with 12° mechanical (24° at the crankshaft) + 12° initial for 36° total advance all in at 3200 RPM. I'm also running full manifold vacuum advance.

I removed the TCS system including all the wiring and the idle stop solenoid. I used the 12 gauge pink idle stop solenoid wire to power the Petronix module I installed in the distributor. This large pink wire is controlled by the ignition switch and was perfect to power the Petronix module. The truck idles and runs much better with this tune.

I had forgotten about the connection of the idle stop solenoid to the TCS system. Good, clear post on the topic!