I expect a '80 SD has a piston vacuum pump? If so you'll notice that the timing device has a rollercoaster-like track upon which the "wheels of the vacuum pump" run. If these tracks are not in a favourable position - so that means the vacuum pump's wheels are not in the dip - rotate the crankshaft (and thus the timing device) so that you don't have to fight against the return spring in the vacuum pump.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!