* Priming the fuel system: If the engine won't start and you suspect a fuel problem (e.g., after fuel filter replacement, running out of fuel), you might need to prime the fuel pump. There's no manual priming bulb or lever on a Ford Transit 2.5 diesel. The fuel system is typically self-priming. You'll likely need to crank the engine repeatedly (with the ignition on) to allow the fuel pump to build pressure. If this doesn't work, there's a more serious underlying issue (blocked fuel filter, faulty fuel pump, etc.) requiring professional diagnosis.
* Priming the fuel injector pump (indirect injection): Older indirect injection diesel engines *might* have a manual priming pump on the fuel injector pump itself. This is less common on newer vehicles. If your Transit has one, check the fuel injector pump for a small lever or pump. It would require consulting the vehicle's repair manual for the exact procedure.
* Something else entirely: The phrase "prime" can refer to getting something ready for operation. If this is the case, please be more specific. Are you referring to a specific system (e.g., the power steering pump, the coolant system)?
In short: For a modern Ford Transit 2.5 diesel, simply cranking the engine (with the ignition on) is usually sufficient to prime the fuel system. If it doesn't start after repeated attempts, you have a deeper problem that needs professional attention. Always consult your vehicle's repair manual for the correct procedures.
