Wuttin

Team,

79 L82, auto/AC car, original Q-Jet.

The tab that connects the wire to the carburetor idle stop solenoid broke off while wrenching yesterday. Is it safe to run the car without this part (my guess is yes it is safe). Do I need it at all? What exactly does it do?

Thanks, Steve

SIXFOOTER

Yes it is safe to run it. The solenoid is there to STOP the IDLE (diesel) when you turn off the key

pws69

The solenoid is there to prevent the engine from stalling when the A/C is on - when A/C = ON, the solenoid is activated and holds the idle higher.

Wuttin

OK, now I'm starting to think it NEVER worked since the tab was loose from the start. Whenever I turned on the AC and stopped at a traffic light or drove at slow speed I would stall. Learn something new each day...

I should be able to check for continuity by using a meter on the green wire and switching on the AC to look for current, correct?

S489

another way: use the volt scale and look for 12 volts

vettfixr

Idle solenoids were used two different ways. On my 74 the idle solenoid was used to prevent dieseling when the car was turned off. The idle stop solenoid was set so the engine would idle correctly and when the ignition was shut off it disengaged and allowed the carb to close completely. On later models I believe it was used to increase the idle when the AC was on. An easy way to check it would be to measure voltage at the line. If you have 12 volts or better when the ignition is turned on but the AC is off the solenoid was used to control dieseling. If you have no voltage with the engine running and the AC is off try turning the AC on. If you get voltage at that point the solenoid was used to increase the idle when the AC is on. Good luck.

S489

vettfixr - did your vette have factory A/C? i see it looks like it did in your pics. my 74 had A/C and the solenoid was used to increase the idle with the A/C on (so that no chnage in idle speed could be detected). if they came both ways, i wonder what determined which way they would be wired? northern vs southern maybe? i think i'd rather have the thing wired to the A/C if i had a choice . . .

pws69

I don't recall that they ever used one for "preventing dieseling" on Corvettes - only for the A/C - Idle issue, HOWEVER, them's some pretty old and abused brain cells so I could be wrong!

vettfixr

No, my 74 definitely had the solenoid controlling the dieseling. It says so in the factory repair manual. One other possibility is the fact that mine is a 4 speed car. They might have used the solenoid for the AC on automatics since the idle on those would drop more than a car with the clutch in. BTW, my car was factory air.

CCrane65

vettfixr, my 72 is the same way as yours and I need the idle stop solenoid becasue my car dieseled from time to time without it. Now that I have it installed no more dieseling.

But, there is a flip side to that coin. The solenoid is not strong enough to push the accelerator linkage when you turn the key on so you have to turn the key to the on position, push the gas pedal slightly so the solenoid can extend then let off the pedal and the car will start. If you don't do this the accelerator linkage will stay shut and the car won't start.

Before the advent of electronic fuel injection, I was always taught to push the gas pedal once and let up BEFORE I turned the key on. Well, that feeds the initial shot of fuel into the carb but you won't get any air if the solenoid can't extend.

Probably why they went away from using a solenoid to stop dieseling.

Just a different way of doing things.

cc