idle solenoid

[davidlive]

Currently my 1978 403 has a vacuum idle system for when it's placed in drive (that's not working), has anyone replaced it with a modern electric idle
solenoid ? or can it just simply be done away with completely ?

Thanks David
--
1974 G-M-C Painted Desert #136
"Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit
the wall, and torque is how far you take the wall with you when you hit it."

 

[chris tyler]

Are you sure its a vaccuum idle solenoid? Curious to see a pic of this

I have seen some Qjets that have a second vac break on the same side as the secondary dashpot which I think was to help pull it off choke when warmed
up

Many cadilacs of the era had an elctric solienoid that closed witht he engine off to prevent dieseling. Others have one that raised the idle when the
AC was on

You can get aftermarket ones - Eldelbrock and others, some engineering required
--
76 Glenbrook

 

[davidlive]

Chris, i was told it was for when it would be put into drive, but you might be onto something there were it's for the a/c
here's a picture of it (at the top in the middle of the pic)
http://s3.photobucket.com/user/DavidLive/media/1978%20GMC%20motorhome/IMG_20170213_153459_zps4sqx02gv.jpg.html

My Vacuum hose schematic is as follows as well
http://s3.photobucket.com/user/DavidLive/media/1978%20GMC%20motorhome/vacuum_zpsr1syvsid.png.html

Thanks David
--
1974 G-M-C Painted Desert #136
"Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit
the wall, and torque is how far you take the wall with you when you hit it."

 

[chris tyler]

Im not sure about this one, as I havent seen this type before. The ones I recall were electric

looking at it, the Idle stop screw isnt engaged- the choke is on so it is on high cam to increase idle when choked.

From the looks of it, that device would be spring loaded, hlding pressure on the linkage until vacuum was applied, then taking it off. But it isnt in
contact when off. Strange...

I suppose if the electric valve is energized any time the AC is off, it would work for AC/high idle- but that seems backwards, and if thats the case
it may not be adjusted correctly. With no power or vacuum Id expect it to be contacting the linkage.

THat would be backwards for an anti dieseling solenoid as well, as you would want to close the throttle when off.

If you want to replace with electric here is what Im talking about : https://www.summitracing.com/parts/smp-es38

Looks like you had a little ,mouse problem. Among others , I see a vac line chewed through to what I think is the spark ported vac part [which only
opens above idle]

My practice on mine and similar vintage vehicles? I get rid of the TVS lines, run spark ported vac direct to the distributor and adjustable advance
canister , with more initial timing and limited total advance. That seems to keep the idle up enough when the ac was on [well, when it worked]

Opinions will vary on this, some say the TVS is needed for cooling, ect., but I find when the mixture and timing is right it isnt a problem. THing is,
you have to be willing and able to tune and not just go by the book setting. I find its far more simple, works better, and gives better response.
Opinions will vary.

--
76 Glenbrook

 

[hal stclair]

The book shows an engine stop solenoid that comes from the neutral saftey switch. Seems a strange set up as its only energized when in gear according
to the wiring diagram. X7725 manual
Hal
--
1977 Royale 101348,

1977 Royale 101586, Diesel powered,

1974 Eagle Bus 45',w/slideout

 

[davidlive]

Chris, yeah there was a rat problem, I've caught him and replaced hoses and figured out where they went.

Hal, that was my understanding as well, so i thought of it as a system to kick up the idle when in drive/reverse while the engine is under load, which
is what bought me to think about just using an aftermarket electric idle solenoid instead ? instead of using vacuum etc.

I think i'm going to try and rid myself of the system first and see where it stands.

Thanks David

--
1974 G-M-C Painted Desert #136
"Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit
the wall, and torque is how far you take the wall with you when you hit it."

 

[les burt]

Looking at that vacuum actuator, I think Chris has described the operation backwards. Most vacuum actuators have a diaphragm that is sealed at the crimp of the canister. Actuator operation is determined by what side of the diaphragm the vacuum is applied. The vacuum port on the actuator in question is on the rod side of the crimp, indicating that a vacuum would extend the rod. Therefore, the actuator appears to be springloaded in the retracted position, with vacuum forcing it to extend. This minor detail would completely change how we interpret or diagnose its actual function.

Other than that, I have no personal experience with the system in question.

Les Burt
Montreal
'75 Eleganza 26'
The EWIP (Eternal Work In Progress)

>
> Chris, yeah there was a rat problem, I've caught him and replaced hoses and figured out where they went.
>
>
> Hal, that was my understanding as well, so i thought of it as a system to kick up the idle when in drive/reverse while the engine is under load, which
> is what bought me to think about just using an aftermarket electric idle solenoid instead ? instead of using vacuum etc.
>
>
> I think i'm going to try and rid myself of the system first and see where it stands.
>
> Thanks David
>
>
>
> --
> 1974 G-M-C Painted Desert #136
> "Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit
> the wall, and torque is how far you take the wall with you when you hit it."
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[chris tyler]

Les, You may well be right, that way the operation would make more sense.
Hard to tell from pics.

It seems like an electric solenoid would be much more simple and cheaper, but perhaps a reliability issue?
--
76 Glenbrook

 

[davidlive]

Les is right on it's operation, i went out to it and pulled on it, and it sprung back in, so the vacuum would push out, i still plan on removing it
first in the next few days and seeing how it goes without it, otherwise i'll get a electric one, and i would guess it would be more reliable then a
non-functional one i have now though.

I'm just wondering if anyone else has replaced it or removed it completely.

Thanks David
--
1974 G-M-C Painted Desert #136
"Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit
the wall, and torque is how far you take the wall with you when you hit it."