The trouble is when I turn the engine over by hand to adjust the valves. When I turn the engine the cam with flip from the point of least friction to point of least friction. This is happening because the tensioner is not keeping pressure on the chain as it should.

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1998 Mercedes E300TD

1983 Mercedes 240D Turbo, 131bar injectors, Cosworth intercooler and 63' Ford Falcon radiator, Ardic Parking heater, Headlight wipers, Best 38.6mpg.

1973 Saab 96 Rally Car, 1.8l V4 with all the race bits

Maybe the vacuum pump (riding its little "roller coster' track) is causing the problem.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

I use the PS pulley bolt to rotate the engine. The compression isn't an issue with the slack, basically I start to rotate the engine, the chain tensioner compresses, the cam does not turn. Then when the tensioner cannot travel in any further the cam starts to turn. Because there is slack on the other side of the chain the cam rotates on its own from the force of the valves, till the slack is taken up or it finds the lowest point of force from the valves.

Has anyone else seen there tensioner full in when rotating the engine for a valve adjustment?

__________________
1998 Mercedes E300TD

1983 Mercedes 240D Turbo, 131bar injectors, Cosworth intercooler and 63' Ford Falcon radiator, Ardic Parking heater, Headlight wipers, Best 38.6mpg.

1973 Saab 96 Rally Car, 1.8l V4 with all the race bits