Jimny timing belt broken

As Busta says, timing chains, especially hyvo ones, don't just snap without warning.

More likely the plastic tensioner blade has snapped and the chain is slack.
If you are very very lucky, you might get away with a new tensioner blade, as long as the pistons didn't hit the valves when you were trying to start it.

I'd cross my fingers, change the tensioner blade and do a compression check.



 

The plot thickens here........I decided to crank the engine slowly and personally see what happens now that I had the rocker cover off. The engine turned effortlessly and took up the sagging between the two camshaft gears.
It now appears as though the chain may have stretched or the tensioner is dodgy as suggested. It also may have jumped a few teeth,
We will now proceed with further investigation and see if any damages occurred..
Thankyou all for good advise and well done to those who were were reluctant to believe the broken chain theory.

The lack of awful noises still makes little sense though, even if it's just the slide that's failed I really would expect it to sound bad. Good luck with it and keep us posted.

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It now appears as though the chain may have stretched or the tensioner is dodgy as suggested. It also may have jumped a few teeth,

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It may not have jumped teeth, there is usually a small lip under the crank sprocket that will prevent the chain dropping far enough to disengage.

It is a tensioner problem for sure, something has broken. It may have suddenly let go (the blade snapping or the pivot bolt shearing or tensioner failure) which is why you didn't hear the chain slapping around.

What happens is it will run at speed and all the slack ends up on the tensioner run, usually noisily hitting the engine and trying to chew through the side. At tick over, the cams flick backwards and forwards as the valves are trying to close by moving off the point of the cam lobe and the valve timing goes to pot, which is why it won't start.

Depending on how much interference there is valves that haven't shut may contact the pistons. If they did touch, they bend slightly and won't seat, so you lose compression, and the valve clearances will be larger than spec.

Just pull the timing cover and see what is wrong before worrying about anything else.

Once the tensioner is fixed you can check the timing, and if it is still correct just check the valve clearances while you have the lid off, and if they are in spec, just drive it
If out of spec. do a compression test, and if it fails the head will have to come off to sort out the valves.


Whatever you do, don't disturb the cylinder head unless you need to repair the valves. A new gasket is ££££££, you probably need new bolts if they are stretch bolts, and it is aloominums which means it will likely warp and need a light skim to get if flat for reassembly.