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Timing Belt


Ray123
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I,m considering changing the timing belt on my Bora 1.9 TDi. Apart from a lot of dismantling it seems reasonably straightforward. When refitting the new belt the Haynes manual suggests removing the "fuel injection pump sprocket". Does anyone know why this is as I cannot think why this is necessary, as the timing would not be affected if the new belt was just put on with the sprocket in its original place. Are there any other problems to look out for. Thanks.

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Which engine are you doing this on? The new pd engines don't have an injection pump sprocket. The old VE pump engines have a locking pin which holds the sprocket in exactly the right position to make sure the timing doesn't get slightly out, and the whole procedure needs to be checked with Vac Com to set the injection sequence correctly. New single use bolts are required for the engine mounts when replacing the belt, and new single use bolts for the pump sprocket when setting the timing.

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The one I have is the 90 BHP from July 2000. Is it possible to set the timing myself or would it be ok to replace the belt without doing this. I still dont understand why it is necesssary to remove this sprocket as I would have thought the timing would not be affected if the belt is replaced in the correct, original position without removing it at all. When you say VAC Com, I'm afraid I dont understand?? Thanks. Ray

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Right, 90bhp requires the complicated procedure outlined above. The old method of "mark & pray" where the sprockets and engine block etc. are dabbed with a splodge of paint, the belt removed, and then the new belt fitted while lining up the splodge marks is not going to work for you. If you're really (REALLY) lucky you might get it to start afterwards and run more or less correctly, but the injection timing will still need checking with a computer diagnostic system such as the dealers system or Vag Com (an aftermarket cable and computer program available from Ross tech). If you're unlucky, you'll destroy the head and bend the con rods in your engine. I know of documented cases where people have tried following the correct procedure and still knackered their engine.

Basically, the procedure uses locking pins to make sure no components move during the change (so removing the sprocket sounds like a non starter to me), an engine support to hold the engine in place while you remove the mount to remove and replace the belt, new bolts fitted to the mount (do not use the old ones or the engine will fall out later) and then the injection timing setting with the computer, and then new bolts for the injection sprocket. Or something like that.

If you get the belt one tooth out of place, the pistons hit the valves and the damage is done.

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Thanks for your trouble with this, it all sounds a bit dangerous. I've done quite a few belts on other cars without problems. I can see the dangers of the belt being in the wrong position on any of the sprockets but if the new belt went back on in the exact position as the old one, ie if the the number of teeth between runs was the same as the original, then would that be ok or does something go out of adjustment just by virtue of taking off the old belt??? Thanks Ray

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