Purpose of idle solenoid?
Corey Vandiver
I'm trying to adjust the idle speed screw and I can't set it below the
solenoid plunger.
What is the purpose of this solenoid. Someone told me it was for
the A/C, but I don't have A/C. Can I unplug it?
Thanks
corey
Steve Benson
>From: Corey Vandiver <cvan...@lsac.org>
>Subject: Purpose of idle solenoid?
>Date: 3 Jul 1995 16:41:44 GMT
It is an anti diesel solenoid. No kidding !
It was put there so that the car would idle at 800 rpm (a guess at the actual
spec) and when you shut the key off the solenoid releases and shuts the
throttle plates down to the setting of the idle screw which would be 500 rpm.
By shutting the throttle plates closed it would prevent the engine from
dieseling (running on) {at least this was the theory}.
>corey
Andy Dingley
> I have a 71 chevelle with a 307. It has a idle solenoid on the carb.
> I'm trying to adjust the idle speed screw and I can't set it below the
> solenoid plunger.
There are two sorts of "idle solenoid"
One sort is for controlling the fuel supply to the idle jet, If you have a weak
mixture for good emissions control, the engine will tend to run hotter and
"run-on" if the ignition is cut. The solution for this is to have a solenoid
that controls the fuel supply to this jet, and stops the engine dead when
the ignition power is cut.
The solenoid works by being energized when the ignition is on, thus
opening the fuel valve. Some of them are wired to an oil pressure relay
(like an elctric fuel pump). Faults are common with carb mounted solenoids,
particularly these ones. Symptoms are a car that starts and runs fine, but
won't idle. The problem is often electrical and outside the solenoid,
particularly the crimped terminal. If the solenoid is faulty, then "get you
home" measures are to increase the idle speed with the throttle stop screw,
or to remove the solenoid, snip off the needle valve tip, and screw the
solenoid back in.
Some carbs have more than one of these solenoids, to control additional
jets. They may also have decceleration over-run cut-ous, that shut the
fuel off when coasting.
The second sort of solenoid is a "fast idle" solenoid. When energized, it
increases the slow idle speed to a fast idle by acting as a secondary
throttle stop. It may be used to speed the engine up either when aircon
is running, or connected via a thermoswitch as a cold-start device.
> What is the purpose of this solenoid. Someone told me it was for
> the A/C, but I don't have A/C. Can I unplug it?
Probably the second type. Removing it may cause problems with
cold starting - check the wiring chart first.
If you have the screws set right out and it's still idling too fast, check
for bent/distorted linkages, air leaks, and over-rich mixtures.
--
Andy Dingley din...@codesmth.demon.co.uk
If Pte. Clegg is released without a similar gesture towards Republican
prisoners *immediately*, we can kiss the whole peace process goodbye.
Mike Peck
>
>I have a 71 chevelle with a 307. It has a idle solenoid on the carb.
>I'm trying to adjust the idle speed screw and I can't set it below the
>solenoid plunger.
>
>the A/C, but I don't have A/C. Can I unplug it?
>
>
>corey
Corey,
There's a hex head on the solenoid plunger. That's what you're supposed to
adjust to adjust the idle. The screw on the carb is for minimum air adjustment so
the engine will die when the solenoid disengages. The solenoid should pop out
when the ignition is turned on. You will have to open the throttle blades for it to
do that. It will hold the throttle open once it had energized.
Mike Peck /// Peck Auto Supply /// Decatur Il
George B
Corey Vandiver <cvan...@lsac.org> wrote:
>I have a 71 chevelle with a 307. It has a idle solenoid on the carb.
>I'm trying to adjust the idle speed screw and I can't set it below the
>solenoid plunger.
>
>What is the purpose of this solenoid. Someone told me it was for
>the A/C, but I don't have A/C. Can I unplug it?
>
>Thanks
>
>corey
Sometimes that solenoid is to kick the idle when you go all the way to one
side with the power steering. It keeps the engine from konking out when you
try to get into a parking space.
It's your car and you may unplug whatever the government says you can but I
would check out the adjustment for that solenoid before I disconnect it (they
are usually adjustable).
George Bonser
gr...@cris.com
binger
Actually, the solenoid is part of a primitive Emission Control System. The
solenoid keeps the carb slightly open during high-vacuum situations (like
going downhill with your foot off the gas).
The solenoid opens and closes, "porting" vacuum to the vacuum advance on the
disrtibutor, advancing and retarding the spark under various conditions.
The when properly connected, the solenoid is electrically operated by a
pressure switch that's located on the front passenger side of the tranny.
(don't ever try to find a replacement.... trust me) The pressure switch
opens / closes, activating the solenoid to up the idle and advance the
timing at the same time.
In theory, this lowers the emissions.
Chilton manuals don't have much to say about this system, but early "Motor"
manuals (like the one my friend has) *do* cover this in basic detail.
The solenoid, as I recall, is not intended to be used as an idle adjustment
per se, but can be moved forward and backward in its bracket, thus adjusting
the idle. The plunger on mine didn't seem to have any effect on the idle.
Hope this helps,
binger
bin...@hsh.com
(formerly doing mechanical repair on a '71 Nova and a '72 LeMans)
Spud
higher than curb idle rpm (800 rpm) when the car is in Drive (curb idle spec'd at 650 rpm). My
guess is that the doohickey is supposed to keep the engine from dying under load.
Mine has a threaded shaft that enters the plunger, with a locknut. I backed off the shaft and
readjusted my idle, since the solenoid on my Olds crapped out and I'm either too cheap, too
lazy or both to replace it.
Spud
Brandon894
air on. It should be adjustable, but try replacing it. If it is stuck in
one position unplugging it will not make a difference.
Brandon