2000 S70 Timing Belt: Why the VVT Preload?

[abscate]

Here is another thread showing how sensitive the VVT is to timing belt setpoint. Probably what was hapoen8ng here was the cam flanks were in range with the old timing belt,and a simple change of components induced enough shift that they went out of range.

I’ve written up how to use cam flank measurements to determine your timing error and correct systematically, indexedunder. ECM 644A

[SCP74]

I'm in a similar situation, but have not put timing belt back on. My Volvo tech locally said I should definitely reload them before starting back up. That's without any code or start up of the engine. That is where the timing will be set he told me.

[Robbo1983]

I have the same issue. B5254T3 engine, which I believe has vvt on both intake and exhaust. Timing fine but vvts have unloaded.

How do you reload the vvt to spring back into position? I note 90 degrees CW and back but I've had no luck with that. And exhaust Cam rest position was CCW to the timing marks.

[abscate]

Some VVT are sprung and some are not. With the belt off , up you can twist them and see if they spring back to the original position. To put the belt back on you have to pass the marks clockwise, then return to the marks

[Robbo1983]

Thanks abscate. I have another thread open with my specifics if you could review? However, in terms of the spring back, my exhaust cam did at one point but now it won't before belt install. You can move it full circle (pistons moved so no valve contact), but it won't engage the spring lock to rest position.

Reviewing the Volvo manuals, it says the b5254t3 engine has dual vvt. Neither will spring back. I've timed my engine and it cuts out after 10 secs. Throws codes ecm 643a and 664a.

I didn't touch the vvt units on rebuild. They were marked in paint on the rotor, cam pulley and head and these still align. But the ecm detects they are out.

Any ideas? I assumed it was due to the cams not engaging the spring? So was looking how to load them without success.