Ok on my 91.5, I bought the correct clock spring and correct switches from the dealer to converter to cruise, bought a used servo off cumminsforum and got everything hooked up.

If I'm crusing at 60 and set the cruise, it will stay steady for 10-15 seconds then slowly slowly creep up, like it won't stay steady on 60 where i set it....Also doesn't compensate for going downhill or up hill. when going downhill the speed goes way high and when going uphill it slows down as much as the cummins will let it, but the cruise is still set

Over 65mph it seems to work great, stays nice and steady.

And the worse thing of all is If it's set and i go to push the accel button to up a few mph, it literally puts the pedal to the metal like WOT and starts taking off like a bat outta hades until i hit the brakes.


It's almost like the cruise is not getting a signal from my VSS,

Now my truck was a factory NON-cruise truck, but because it's an LE it DID have the wiring in the column, everything was plug and play. Mark Nixon helped me confirm this.

I'm so close to having it working perfect! I'm thinking it's just because my truck has so much more power than stock, and takes less throttle to give a certain amount of speed. Or the servo is bad.

 

I had the same problems with my 98 12 valve after I modded it. Cruise never worked well after and had the same symptoms your's does.

 

It doesn't sound like a problem because of increased power if it works fine over 65 mph, maybe an adjustment issue of the linkage from the servo to the throttle lever?

 

Does a stick truck have a tps? If you want to bring the truck to my house brandon I will put my scanner on it and that will probably help you narrow it down.

 

If you hit "set/coast" or the brakes does it disengage the actuator?

 

If you have the throttle linkage on the inside hole on the pumps bell-crank your cruise control will be very twitchy, your throttle geometry have increased significantly.

At least it was on mine.

Jim

 

Ok I'll move it to the outside hole.

And yea if i hold the "DECEL" button it will kill the cruise until i let off the button on the desired speed i want....

Also tapping the brake pedal will kill cruise as well.

 

Tapping the brake should kill the cruise until you reset it.

 

Yea it does kill it.

 

I seem to recall 12 valve guys putting an adjustable air bleed (read needle valve) in the vacuum line to the servo to deal with the twitchy response.

Sent from my HD2 using Tapatalk

 

That sounds like a great idea Thanks Faith.

I'll have to see if they have anything at the hardware store.

 

Mine will take off and speed up randomly if the potentiometer is not set properly. Does a stick truck have a tps?

 

No TPS.

the other night I pushed ACCEL and of course it started to rapidly speed and then i held the DECEL button to bring it back down, and when i let off the DECEL button it literally floored it, blacked out the whole road and i was going 80 before i knew it.

It's so unpredictably insane. I gotta figure it out.

 

We can look at the Target speed and cruise servo voltage with the scanner while we are driving if you want to bring it down I will help you check it out.

 

steady vacuum you need a large tomato/ coffee can for a reserve for the vacuum actuator to make it work they had the same problems on some of the early diesel gm cars in the 70s also have you set the parameters on the control box should be three potentiometers on the side for the cruse forget what each does but you have to drive the truck/car and a just with a small screwed driver