King Control Throttle and Cruise Control Issues
by Barry Leavitt
Your (and our 1997 U270) uses a 'fly by wire' throttle where the throttle rotates a resistance control that tells the throttle controller located in the back corner of the engine compartment on the curb side what the throttle position is. This controller was developed by King Control, the same guy later developed the King Dome satellite antenna.
The King throttle control was obsoleted by electronic engines and one of the lead King Control employees bought the throttle / cruise control business and runs it under a different business name. He is very helpful and knowledgeable and is located in Minneapolis MN area. He has worked on our controller and I recommend anyone who has a King Control and is in the area to stop at the plant.
Prior to the use of the King Control, throttles were controlled by an air cylinder. Motorhome manufactures about 1995 asked King who was supplying the cruise control if they could create a electric throttle for the Cummins engine. This included Foretravel, Monoco, Country Coach, etc.
But within about 4 years, Cummins came out with electronic computerized engines that included throttle and cruise controls and King was no longer needed for new coaches. But there was and still is a need for cruise controls to be added to older big trucks, so King still has a potential market. And is also servicing their short lived motorhome OEM installations.
The cruise control relies on the brake light circuit to know when coach brakes are applied, so it can safely turn off the cruise control when brakes are applied. To be sure the brake light circuit can be 'seen' by the cruise / throttle control (which is the same circuit board) the controller must see a resistance through the brake light bulb to ground. If the brakes lights appear to be burned out or otherwise malfunctioning the King Control will only allow about 5 to 10 MPH of throttle control.
If everything is ok with brake lights, the King Control can be malfunctioning and a new board can be ordered from King Control. Board is not hard to install, but a new gasket must be installed to keep the cover sealed from moisture.
When a throttle does not work, a temporary work-around has been reported that is being called 'fly by rope'. The bed is raised an inch with a board placed to keep the bed up. A rope is attached at the engine lever that increases fuel flow, which was normally moved by the King Control. The other end of the rope is up front by the dash and one drives by pulling forward on the rope. Normal throttle springs pull the throttle back to idle position.
By the way, these two throttle springs sometimes break and this can cause run away engine RPM. Check that both springs are in place. Replacement springs can be made from regular hardware store matching springs. Better to have a spare or replace them before one breaks.
Photos by Bill W.
| Throttle Springs | Get it home throttle kit | Throttle cable - bracket |
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| King Control | Air Throttle | TPS Sensor |
Cruise King Service
Steve Boller, owner
11200 Hampshire Ave South
Bloomington MN 55438
952-944-9644
651-398-5555 emergency only (cell phone)