very good, now that we know what it actually is it will make things go easier ;o)

if it will crank but only idle
mrfixit suggestion was a very good point to check
i'd still check the things i said to check and i'll add one more thing as i had a very similar problem with a lift before, the diaphram in the mixer wasnt operating correctly and not seating properly and wouldnt let the lift run/accelerate. But the throttle plate/governor or accelerator/throttle body sounds more like it to me.
i believe someone already asked about if it had a throttle cable or does it have electronic throttle body?( i believe his terminology was "drive by wire")

more things to ponder while troubleshooting ;o)