1. Air in the Fuel System: This is the most common problem. When you run out of fuel, air gets sucked into the fuel lines and the fuel pump. The diesel fuel pump needs fuel to lubricate itself; running dry can damage it. The air prevents fuel from reaching the injectors.
* Troubleshooting:
* Bleed the fuel system: Your truck likely has a manual bleeding system. Look for bleed screws or valves on the fuel filter, fuel pump, and possibly injectors. Loosen these screws one at a time, allowing fuel to flow and purge the air. Tighten them as fuel starts to flow steadily without air bubbles. This process requires patience.
* Check the fuel filter: While bleeding, inspect the fuel filter. If it's clogged or damaged, replace it. A clogged filter can exacerbate the air problem.
* Prime the fuel pump (if applicable): Some diesel systems have a manual primer bulb or lever near the fuel filter. Pump this repeatedly to force fuel through the system.
2. Damaged Fuel Pump: As mentioned, running a diesel engine dry can severely damage the lift pump (which draws fuel from the tank) or the injection pump (which delivers high-pressure fuel to the injectors). A damaged pump may not be able to create enough suction or pressure to deliver fuel.
* Troubleshooting:
* Listen for the fuel pump: When you turn the key to the "on" position (but not starting), you should hear the fuel pump running briefly. If you don't hear it, it may be faulty. This is often a harder diagnosis and may require a professional mechanic.
* Check fuel pressure (advanced): If you have a fuel pressure gauge, you can check the pressure at the fuel rail. Low or no pressure indicates a pump problem. This usually requires specialized tools.
3. Low Battery Voltage: Cranking the engine for an extended period while trying to start it (especially after air in the fuel system) can drain your battery.
* Troubleshooting:
* Jump start the truck: Try jump-starting the truck from a fully charged battery.
4. Other Electrical Issues: A faulty ignition switch, starter motor, or other electrical components could prevent the engine from cranking or starting even with fuel. This is less likely if the engine was running fine before running out of fuel.
What to do:
1. Start with the fuel system bleeding: This is the most likely culprit. Carefully follow the bleeding procedure for your specific truck model. Consult your owner's manual or a repair manual for detailed instructions.
2. Check the fuel filter: Replace if necessary.
3. Listen for the fuel pump: If it's not running, investigate further.
4. Consider professional help: If you've tried these steps and the truck still won't start, it's best to call a mechanic experienced with diesel engines. They have the tools and expertise to diagnose more complex problems.
Safety Note: Diesel fuel is flammable. Avoid sparks or open flames while working on the fuel system.
Remember to consult a repair manual specific to your 1994 UB diesel truck for detailed diagrams and procedures. The exact location of bleed valves and the specifics of the fuel system will vary depending on the make and model.
