Bleed the Thornycroft T90 Fuel Injection System

Tools needed: 8mm wrench, container for fuel drainage, clean rag.

Safety Precautions: Wear eye protection to prevent fuel spray. Ensure the engine is off and the area is well-ventilated.

1. Verify the fuel tank valve is fully open and the tank vent is clear to ensure gravity flow.
2. Locate the two bleed points on the fuel injection pump: the 8mm screw on the side and the secondary point on the top.
3. Place a rag under the bleed points to catch excess fuel.
4. Loosen the 8mm side bleed screw. If using the top bleed point, hold the nut underneath with a second wrench to prevent the union from rotating, which can damage internal pump settings.
5. Crank the engine briefly until fuel emerges from the bleed points without air bubbles. Tighten the bleed points once solid fuel flow is achieved.
6. If the engine still fails to start, loosen (crack) the injector pipe unions at the injectors slightly. Crank the engine again until fuel emerges under pressure at the injector ports.
7. Tighten the injector pipe unions securely and attempt to start the engine.
8. Verify the fix by ensuring the engine runs steadily; repeat the bleeding process up to three times if air remains trapped.

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