Cowboy_Customs

How does the cruise control work?

Here is why I ask, On all of the semi's I have driven you can set a high idle with the Cruise Control. On my Ford F250 IDI I once had they have a high idle warm up soinoid, and there is a mod to put it on a toggle for high idle any time.

I want to use the cruise control switch to be able to set the idle.

SO, How does the cruise control work exactly??

Crossy's son

Works off vacuum.

Its a vacuum diaghram, the linkage is hooked to the diaghram and the linkage runs to the side of the injection pump, so as you accel. (with the buttons) the vacuum diaghram moves in and pulls the linkage more giving it more throttle.

It hooks up to the hydrobooster, theres a "T" where it goes from the vacuum pump to the brake booster,

It works very simple . And ALL trucks came cruise control ready with the plug already on the drivers side wheel well, the plug that hooks into the dighram.

I believe even the wiring that runs up the column is there, just gotta remove steering wheel to get it out.
All you needed was the buttons in the steering wheel, they started using the different steering wheels in 92 and 93 LE trucks, the early trucks had the cruise buttons that were easy to attach, they were along the bottom of the wheel.

I've seen two 92 trucks that had NO OPTIONS at all and they had the old style steering wheel.

Cowboy_Customs

Good info, but how can you rig it to work for high idle? There must be a feed wire from something, say a speed sensor that triggers something in the cruise control computer to allow you to set it? I know on most vehicles it will only work down to a certain speed, and then its "locked out" untill a certain speed is reached.

I have cruise, im just trying figure out how to wire it up to work at all times basically.

wannadiesel

You're going to have to do a lot of fooling. The PCM has to think you are going faster than 25 mph and that the trans is in gear.

Cowboy_Customs

Hmmm..... thats what I thought. Going to have to find a FSM for the wiring diagram. I have an idea, that once you were to find the "wire" that tells the CC computer the givin info, depending on voltage, wire in a toggle and resistor, to trick the computer, then simply set the idle via the cruise switches......

wannadiesel

The VSS isn't that simple. You gotta do two things: First, fool the PCM into thinking that the truck is going at least 25 MPH. Second, that VSS input needs to vary with engine speed so the cruise will hold speed.

I think a pull cable would be a lot easier.

Jim Lane

If you want a High Idle control you can add one easly by installing an Idle Control Solenoid to the throttle linkage with a simple bracket then you would need to provide ignition switched 12-volts for it through a small toggle switch in the cab.

To use it you would need to engage the switch and then slightly depress the throttle past idle allowing the solenoid plunger to extend, now then you release the throttle the linkage is now being held at your higher preset idle speed.

When High Idle is no longer needed simply turn the switch to off and the throttle linkage will drop back to your normal idle speed.

It is real simple; I used them on many of my vehicles when I needed a faster RPM for my charging system.

Idle Speed Solenoid, also called Anti-Dieseling Solenoid was used on almost every carbureted engine from about 1970 until the Throttle Body was introduced because of emissions higher temperatures and idle speeds, the engine would Diesel or Run-on after the engine was turned off so the solenoids job was to drop the throttle plates completely closed to starve the engine of air.

You should be able to still find than in wrecking yards and get them for a few dollars.

http://www.summitracing.com/parts/HLY-46-74/


I have one planned for my engine.

Jim

Cowboy_Customs

Hey Jim, I was hoping you would pop in on this one! My first thoughts on the idea was to do just that acctually. Like I said up top, all the 6.9 and 7.3 IDI Fords, had a high idle solinoid to aid in start up and warm up. If I cant make it work like a big truck, then thats the route I am going to take, just with the Ford/International setup. And it works just like you said too.

Hey, I just had a brain storm too! On the IDI, The fast idle, and the timing advance were wired in on the same circuit, and connected to the temp sensor, which kicked them off when the engine reached 110*. Using the same modification, as the IDI guys, you can wire them in parrallel to work together whenever the KSB is working and have a high idle every time you start the truck when its cold, and do the Mod, to have it on a toggle!

The IDI start up procedure was Key on, step on the throttle to extend the high idle plunger, release the throttle, and start the truck. And the high idle solinoid is adjustable. When the temp reached 110*, the timing advance and high idle kicked off.

The IDI mod included a toggle and resistor so as to not activate the timing advance and still have high idle. I can find the write up for it if your interested in doing it like that. I think thats how I might do mine now that I am thinking about it.

sdstriper

The idle control for bigger truck PTO use etc is run with electric cruise control. No vacuum thingies involved, just electric. These are readily available online etc. in kit form, universal electric cruise control, approx. $200 and up.

Billut

on a side note: when the pump was turned up on my truck, the cruise control starting to act differently: it would not hold the set speed as soon as I hit the beginning of a hill for example. Is this related to the vacuum, or else?

Jim Lane

Resistor or a Diode?

I could visualize the mod using a diode connecting the Idle Solenoid to the Timing Advance Solenoid circuit.

When the factory idle circuit was initiated power would activate both solenoids but if it was backfed through an auxiliary switch the Idle Solenoid would be activated but the Advance Solenoid would be blocked.

Maybe I am thinking of a different way of achieving the same end results.

Also if you were to install an indicator lamp or an LED to indicate the High Idle was engaged you need to make sure that you install a quench diode across either the solenoid the lamp or the LED because when the power is removed from the coil the field will collapse and it will induce a several hundred volt spike back through the lamp and quickly destroy it, Again a very easy circuit.

Jim

Jim Lane

I am not sure of what all you have done to your pump but.

When I tried changing the throttle linkage from the outside to the inside hole on the injection pump the Cruise Control becomes extremely twitchy to where it was unacceptable.

My thinking is because it changed the geometry between the CC servo and the throttle position and proportionally magnified the servos hunt as it tried to maintain the vehicles speed.

Jim

wannadiesel

Try restricting the vacuum with an orifice. The cruise does not expect the engine to be as responsive as it is now.

Rickcher

Not trying to hijack this thread, but my cruise control quit working yesterday. Does the cruise work strictly off vacuum? Does the cruise switch on the steering wheel send an electrical signal to the diaphragm? I'm just trying to get a handle on how it works so I can troubleshoot it.

Cowboy_Customs

Ahh, you are right Jim, it is a Diode. Here is a link to the IDI tech article for reference. http://www.oilburners.net/articles/h...20override.htm