Originally Posted by
sctrailrider
Being a 93 it's a manual injection pump motor, no computer. You should start with checking or changing the fuel filter & air filter, the Glow plug system would be next, the lift pump is mounted on the frame rail under the driver side of the cab, with the motor idling, open the filter drain valve, it should be a brass "T" looking thing mounted to the thermostat crossover, if the motor stumbles or quits the lift pump isn't working.
Look it the "stickys" at the top of the forum list, I think their is a list of things to check better than what gave..
Anyway, try these things and report back...