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For a Ford Focus mk1, 1.8 tdci, 74kw from 2004, I see that the timing belt only links the camshaft to the fuel pump. The crankshaft and the camshaft are linked through a chain.

Therefore, I was wondering what would happen (hypothetically) if the timing belt breaks in this engine. Since the camshaft and the crankshaft will still be synchronized through the chain, there should be no collisions between the valves and the pistons.

I imagine that the fuel pump will stop sending fuel and the engine will simply stop. Am I right or am I missing something?

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If what you describe is correct, if the belt snaps, the fuel pump will stop and so the cylinders will not be injected with fuel.

The simple answer is the engine will stop.

As long as the broken belt can’t get to the timing chain and cause it damage or to come off, then there should be no mechanical damage to the engine. If a new belt is fitted correctly the engine will work again as normal.

However, if this video is the same as your engine, then it says that the chain goes from the crank to the pump and then there is a belt from the pump to the camshaft. If either of those snap, then the crank and cam can go out of sync and could possibly cause damage depending on the design of the head. The guy in the video also says that some of the engines had chains in oil and some had a belt in oil rather than a chain.

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  • I'm not at all sure now that you show me that video. Looking in the Haynes manual gives the same structure: crankshaft linked to the pump with a chain and then with the belt to the camshaft. If this is the case then indeed, engine damage will occur if the belt snaps. Thank you for the answer. – Beni Bogosel May 9 at 14:30
  • Not all engines suffer damage if the timing belt snaps. – HandyHowie May 9 at 19:59
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The timing is the controlled by the chain so the valve timing will only be affected by excessive wear or breakage of that chain.

The belt driving the fuel pump controls the fuel pump and won’t affect timing but will affect fuel delivery.

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