That may sound like a weird title - let me explain. A bit long but thorough.
In a "gasser" or most conventional front-engined vehicles, there is a cable that reaches between the throttle pedal and the engine. Push the pedal, the cable attached to the engine moves, causing acceleration (or deceleration). Some cars now use "throttle by wire" systems but it isn't all that common yet.
Pushers (as you know) have the engine in the rear but the driver controls the vehicle from the front.
Having a cable (mechanical link) from the throttle pedal to the engine 30-40 behind the driver isn't ideal. My coach, a 1996 Monaco Dynasty (Roadmaster Chassis, Cummins 8.3 and Allison 3060 automatic transmission, King Controls K-2600 throttle / cruise control system) had a "throttle by wire" system. Instead of a cable between the throttle and injection pump, an electronic signal is transferred by wire (hence, "throttle by wire")
. The throttle pedal creates a signal that is sent by wire to a control box in the engine compartment that in turn will pull (or push) on a cable attached to the injection pump (usually to an arm). Push the throttle a little, the control box pulls the cable a little, engine accelerates slowly. Mash the throttle, pedal sends a different signal, control box pulls the cable a lot and you get full power / acceleration. Simple and elegant.
WHERE I HAD A PROBLEM
In 2016, I noticed a problem while driving where once in a while, the throttle pedal seemed to be "dead". I would push on the throttle pedal and there was no corresponding reaction from the engine. Usually a very short time, a second or two and while under way, not a big deal. Things get a little uncomfortable when at a stop light / sign and the pedal doesn't react...
Over the course of about 8 months, things got a little worse. On our last trip in October 2016, we actually had to pull over and come to a stop a few times before I got throttle back. Finally, on our way home (about 125 miles out) the throttle quit altogether.
I chose to take a "MacGyver" approach where I lifted the bed, tied a 50-ft length of paracord to the arm on the fuel injection pump and ran it to the driver seat where I pulled it "by hand" to control the throttle. Not fun but we got home. I ADMIT - not ideal, diminished safety etc. I just wanted to get home.
I am a fairly accomplished shade-tree mechanic / DIYer so I was determined to figure this out. Besides, I don't MAKE $150-hour so I hate to pay that to someone for something I might accomplish on my own.
Mulled it over for a few weekends, decided to start at the front and work back. Removed the throttle pedal from the firewall, ran some electrical tests on it and it checked out fine. I attempted to run some tests on the wires between the pedal and the "controller box" but couldn't seem to get it right. I thought I might have to trace the wires from front to back to find a break etc.
Finally, with my wife helping out, I kneeled down next to the flipped up bed / engine compartment to observe what was happening and/or what I might hear. She turned the key to on (not so far as to crank the engine over) and then I asked her to slowly depress the throttle pedal. I heard some noise but the cable between the controller box and the injection pump arm did NOT move
. AHA!! Now we're getting somewhere.
I removed the six screws from the top of the box and noted a circuit board with some lights etc. I asked her to again depress the throttle slowly and then let off the throttle slowly. I saw a small motor rotating (in a jerky manner) first when she depressed the pedal and the opposite direction when she let the pedal come back up. NO MOVEMENT OF THE CABLE TO THE INJECTION PUMP!! PROBLEM DIAGNOSED!!
After a little bit of searching on the WWW, I contacted Steve at CRUISE KING, LLC (Semi Truck, Bus, RV, Service Vehicle Cruise Control Installation
or (507) 334-0250). I gave him the run-down on the symptoms and what I had discovered. Parts are not available but he does a complete rebuild of the control box and all components for $475.00 with ONE DAY TURN-AROUND time!!
I shipped off my box (cost me ~$20 via UPS) and Steve called me the day after UPS delivered it. He said it was already done and he needed my Credit card info so he could charge me and ship it back. SWEET!!
ON THE ROAD AGAIN!!
I installed the rebuilt controller box this past weekend. Plugged the wires in, connected the cable to the arm on the fuel injection pump and did the visual test of "does the cable move / pull on the injection pump arm when the throttle is depressed?" YES IT DOES!! Turn the key, fire the engine up and push the throttle - WE HAVE THROTTLE response.
"The Bus" drives again without the help / hindrance of a 50-ft. length of paracord.