Pic request. Cruise vacuum dump valve

[cpdenton]

I have been on a mission to get my cruise working. I have cleaned the electrical contacts to the steering wheel which finally got me good control button signals. Checked the modulator electrical connections.

Now, the last thing I need to do is re-mount the vacuum dump valve on the brake pedal. It has never been mounted on my truck. I went to the salvage yard and tried to find one to look at, but no luck. All the trucks they had were no cruise trucks....

Anyone have a picture of how this thing mounts on a 92 model OBS truck?

 

[BDCarrillo]

Is that it??? Pic from my 92

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[cpdenton]

Awesome pic. Thanks. That is absolutely it. Now, maybe I can figure it out!

 

[BDCarrillo]

Need any other photos/angles of it? I can take more pics on my 92 or 94.

Might it be easier to rig up a solenoid in the engine bay to dump vacuum when the brake lights are triggered?

 

[gandalf]

I'll have to admit my ignorance on this. I really have no knowledge about the dump valve. What I will offer here, though, is another picture of that same area as shown in the previous post. Mine is, I believe, from a different direction. If the dump valve is in it, then great. If the dump valve is not there, well, enjoy the picture, and have a happy and safe New Year.

I hope this helps.

 

[cpdenton]

Every picture helps! These cruise systems have a double redundancy. The module has an input from the brake switch. That is supposed to turn the system off, however, this vacuum dump is a backup in case of brake switch failure.

Interesting hing I am seeing here though. My superduty pedal assembly with manual pedals does NOT have a bracket for this vacuum dump.

Btw, this dump works pretty simply. With the pedal all the way up, the valve is closed. When you push the brake pedal, the valve opens thus dumping any stored vacuum in the cruise servo.

 

[BDCarrillo]

heck, have fun trying to get up in there... I could barely fit my phone in to snap a photo!

 

[laserjock]

When you get your system all worked out, I would really, really, REALLY appreciate it if you would do a short write up to cover all the components or just post pics of all the components and where they should be. Someone changed the column in my truck and in doing so removed parts of the cruise it seems. I don't remember seeing that on my 91. I'm not sure what year they went "electronic" but I think it was later in the obs run.

Pretty please!!!

 

[cpdenton]

I will do what I can. I have an EVTM. Best purchase ever. Not very many pages on the cruise, but enough to diagnose it. Not sure if the brick nose trucks use a speedo cable or not. This 92 system has a solid state unit under the dash that controls, not only the cruise, but several other things. I would be happy to post up the diagnostic procedures for a 92.

 

[icanfixall]

Nice pics. Ken thats a good pic of the brake peddle cruise control dump valve bracket and the brake lite switch. I so hate working under the dash. It really hurts my back trying to reach under there supporting myself on the foor to cab edge of the floor.

 

[cpdenton]

So, at this point, I have decided to bypass the vacuum dump valve. There are two other redundancies on the truck besides the off button- the brake switch and the clutch switch. Those are both operational. I have also gone through all th electrical diagnostics and everything is in parameters. I think I have narrowed it down to a faulty cruise servo diaphragm, but I am not exactly sure how to diagnose this without just throwing 75 dollar parts at it.

Anyone have a factory service manual that has the diagnostics for the actual vacuum servo?

Evtm does not cover this.

Thanks
Chris

 

[smokin150]

Check this out http://www.thorssell.net/hbook/ccwire.html that helped me out... I'm in the process now of using the cruise system as an idle bump...

 

[cpdenton]

Thanks. That is excellent wiring schematics. My evtm covers all that pretty well, and I intend to write a tech article about all the diagnostic procedures. Only thing I am missing is the actual procedures to diagnose the vacuum side of the servo. I think I know what I am doing, but I would like to know for sure.

 

[smokin150]

http://www.thorssell.net/hbook/ccptest.html that's the parts testing section... Hope this helps