the cam must come out to get those bolts

you can leave the cam sprocket attached to the chain if it makes you feel more comfortable, but it must be taken off the camshaft

the chain will not fall off the crankshaft or the injection pump gear. There is a separate chain for the oil pump

you will not lose timing if you make marks on the chain in reference to the cam sprocket, and drop the chain... but it is nice to have chain available for access

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