Anti-dieseling solenoid questions
 

I connected my anti-dieseling solenoid on my Rochester carb tonight as it was not getting power. I connected to the 12v coil positive (hope that is ok?)

As I understand the solenoid is supposed to actually control the idle speed and the actual idle screw is only supposed to make contact at shutdown when the solenoid no longer has power.

My solenoid doesn't seem to have enough power to push the throttle idle beyond 800 rpm. That is about what the idle is supposed to be but is my solenoid bad? I put some brake cleaner on it and a little lube so I will see if it improves. Also is how I adjusted it correct?

Re: Anti-dieseling solenoid questions
 

Yours would probably be the only one in the known universe that hasn't been tossed. Set the timing and idle correctly and you won't need it.

Re: Anti-dieseling solenoid questions
 

My 72 has the original solenoid. Works fine. When key is off it retracts. Key on it pops forward opening the throttle to idle speed of your choice. You can adjust the idle while running by turning the square on the end of the shaft. CCW decreases idle and CW increases idle. I find it quite handy while setting dwell, timing, and best lean idle. Of course I don't do that everyday. I guess it's each person's preference.

Re: Anti-dieseling solenoid questions
 

The positive coil wire does not have 12 volts. Have you measured 12 volts at the coil or the solenoid? Why not use the wire diagram to get 12 volts from the original source?

Re: Anti-dieseling solenoid questions
 

I have an aftermarket coil and distro.

Re: Anti-dieseling solenoid questions
 

Majority of these solenoids were on AC trucks and didn't engage without AC on (of course) and the slight depression of the gas pedal to let it actuate. They will not usually just step it up on their own. Base idle is set by the screw on the carb and solenoid adjusted by the hex. Only about a 150-200rpm idle difference

Re: Anti-dieseling solenoid questions
 

My 72 has a/c and this solenoid. Solenoid retracts key off and extends key on without a/c being on. Operation in the service manual.

Re: Anti-dieseling solenoid questions
 

Some old rumors said that it was for AC kick up but I dont think that is true. It was to prevent dieseling when shotting down especially with the fuel in the 70's

Re: Anti-dieseling solenoid questions
 

Easy to sanity check that from the wiring diagram

Re: Anti-dieseling solenoid questions
 

I always thought that it is there for idle kickup when the ac is on.

Re: Anti-dieseling solenoid questions
 

Seems AI may be right for a change.

"An idle control solenoid on a Rochester Quadrajet acts as an adjustable throttle stop to maintain proper engine idle speed when energized (usually by ignition) and allows the throttle plates to close completely when off, preventing engine "run-on" or "dieseling". It often boosts idle RPM to handle electrical loads like air conditioning."

Seems your 72 would be like my 71 was, all kinds of little wires running off the TCS assembly and such to the solinoid. I tossed the TCS, and am onboard with Truckster's opinion, my solenoid found a forever home in a box.

Curious if yours is A/C and has a Anti-dieseling relay in the cab?

Re: Anti-dieseling solenoid questions
 

Mine is AC but no relay I know if. My understanding is that the solenoid maintains the idle speed and when there is no power during shutdown it allows the carb to close all the way starving it of air and preventing dieseling.

I was told to set the idle speed with the solenoid and then put the idle screw right up to touch the plate and then back the idle screw off 1/2 turn.

Re: Anti-dieseling solenoid questions
 

My solenoid isn't retracting like it should, I think the spring broke. Would anyone be willing to put their old one in small box and mail it to me

Re: Anti-dieseling solenoid questions
 

The solenoid has a high current draw and was powered by a 12 gauge pink wire connected to the ignition terminal of the fuse panel. Connecting it to the ignition coil is a bad idea.

The solenoid is part of the TCS system. In an effort to reduce emissions Chevrolet 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 removed my solenoid and recurved my distributor with 12° mechanical advance (24° at the crankshaft) + 12° initial for 36° total advance all in at 3200 RPM. I'm also running full manifold vacuum advance.

I also removed the rest of the TCS system including all the wiring. 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.