King Throttle Emergency Options
My symptom of a failing King Throttle was a loss of power after driving for several hours, usually while climbing with cruise control engaged and manually adding throttle with the foot pedal. The coach would slowly lose power and I would have to pull over, let it idle for a couple minutes and then it would operate normally for days. My first response was to change both fuel filters. This would happen every now and then, but this year it became more frequent, again I changed fuel filters. After an uneventful trip to the Upper Peninsula of Michigan this September and October, it started acting up again. On a trip from Carlsbad NM to Albuquerque I started having trouble a few miles from Cline's Corner when I lost all throttle response and then did not recover after idling or turning the engine on and off following a cool down period. After idling about a half mile on the shoulder, limped into Cline's Corner and parked overnight in the truck parking area. Definitely not fuel filters.
The generally accepted emergency throttle is a rope or cable from the engine throttle, up and over the engine box and connected to a floor mounted hand throttle operated with the right hand while driving one handed. I had seen first hand a hand throttle and a photo of another, both attached to brackets screwed into the floor. I was prepared to make one, but also read on the forum someone was going to put a C Clamp on the accelerator pedal, and operate the rope from there.
I attached a 4 inch C clamp to the top of the accelerator pedal and then made a bowline hitch loop at the end of the ¼" nylon rope and ran the loop over the adjusting lever bar of the C Clamp and then threaded the rope through the loop to create a secure connection to the clamp. This rope was run to the foot of the bed and attached to a carabiner. I made the same bowline loop and threaded the rope around the throttle lever at the engine. I had already made a hole for some heavy wiring at the firewall to install a start battery maintainer in the passenger footwell electrical space. I then took the switch faceplate off the hot water heater switch and ran the rope through a gap on the outside of the electrical box to the rope from the driver accelerator pedal. This meant I had more or less a straight pull from the engine throttle to the front accelerator pedal and did not need to go up and over the bed platform. After a couple of adjustments on the rope length the driver accelerator pedal operated fully from idle to full throttle.
There are four advantages to the C Clamp solution. First, unless you are a helicopter pilot, you will find it more natural to throttle the coach with your foot and drive with two hands on the wheel. Second, you don't have to screw a hand throttle bracket into the floor. Third, your King Control still receives a throttle position signal from your driver's accelerator pedal and IF your King Control transmission position sensor still works, the transmission shifts normally! Otherwise, it will only shift at max pressure or near redline. Fourth, your cruise control may STILL work! Mine did, but then didn't.
Once at Albuquerque I started working through the King Control trouble shooting procedure. I dismounted my accelerator pedal to get access to the Accelerator Position Sensor connections and verified the resistance from idle to full throttle per specs. All good. Took the cover plate off the King Control and it appeared to work just fine. Sent photos of my unit to Brent in Washington and he noticed the burnt connectors at the motherboard. I attempted to remove them and clean them. BAD IDEA. The connector was so brittle it was disintegrating. Retested the throttle and went for a drive. No throttle, so hooked up my rope. Test drive, no transmission TPS and no cruise. Took a chance and pushed on the bad connector and went for a test drive. TPS worked but no cruise. At this point I replaced rope with cable, ran the cable through ¼" PEX at foot of bed to avoid chafing of wires and then continued on to Oklahoma, Texas and then back to New Mexico and home base where I removed the King Control and sent it off to Brent at Advanced Diagnostic Consulting. Still waiting on a refurbished King Control.
In conclusion, don't be lazy and optimistic like me and think the King Control will live forever. Put together an emergency kit and test it. Everyone I talked with experienced an intermittent failure before complete loss of throttle. If you go with an air throttle, you will have to install a stand alone Allison TPS, but you might get away with still using the King Control as cruise. I know two forum members who have a functioning King Control cruise, but no throttle via foot pedal.
The two throttle return springs on the C8.3 are strong. I had to stop every hour or so to stretch my leg without the cruise control. Was it wise to keep driving with my Okie engineered throttle? My great uncle, a dairy farmer, would have said, "Why not?" My great nephew in law, a trained heavy equipment mechanic and ex-Marine, shook his head and said behind my back, "That's crazy."
Photos show cable set up with quick connect at bed and throttle. Easily disconnected to prevent tripping hazard while parked.
Topic: King Throttle Emergency Options