Bob, I am impressed with your ability to track down and resolve this problem. I was especially amused at your early solution, though. The idea of using a hand vacuum pump to keep the truck going at idle was great. The things we will do to keep moving.
"It appeared the steel gear and shaft were becoming magnetized by the wiping action from the camshaft and caused the Hall Effect sensor to get false readings"
Bob, these problems occurs with Hall Effect sensors. When I had done some experiments with Hall Effect sensors, I found that any magnetic field near to the Sensor will be interpreted as signal. This will lead to the malfunction of system, where sensor o/p is served as the input to the system. I had faced similar problem in Brushless DC motor drive, where Hall Effect sensors are using to drive the circuits.
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