New problem

[solarman216]

Seems like my time for problems, I have two Lister 1970s air cooled diesel gen sets, 3 cyl for main generation and a 2 cyl for standby, started the standby last week it ran up fine but as I started to check battery water it died with only a small whiff, thought air in the fuel, but after hitting the starter realised there was no compression, now two independent cylinders?? so thought cam shaft broke? remove oil filler cap and can see both valves going up and down, cam shaft is driven at front of engine so crank shaft cannot be broke as I can turn it on flywheel end, so question, how can both cyls lose compression at the same time about a minute after start up? have not had time to pull it apart yet to find out, maybe time tomorrow, but interested in theories, Rick

[rustic]

I assume two independent cylinders means that they don't share a common cylinder head then.
Otherwise it would look as though the gasket had blown between them.

[Terranical]

Stuck rings?

[exosteve]

If you can't fix it rick.I don't know anyone who can

[solarman216]

Originally Posted by Terranical

Stuck rings?

there is absolutely no hint of compression at all, it is, like there is a hole in both pistons, or the decompressors are down, which of course they are not, and yes Rustic completely separate cylinders and heads, I am miffed as I know every part of these engines, Rick

[solarman216]

my best guess at this stage is that the cam shaft has broke and moved till it is out of sequence so that is why I can see the valves moving but no compression cos it is out of sync, starting handle on the cam shaft could prove it if I can find the handle, Rick

[AlexD333]

I would love to be able to help, but it would be like chucking a new born in the deep end of a pool

The only thing that sprung to mind was something a tech told me about old jag engines loosing all compression so they filled all cylinders with some oil to bulk out rings or some suchthus restoring the compression

I think this might have been for petrol only though..

[Paff]

How is it timed? Can that slip/go out?

[solarman216]

Thanks Alex yes it will work equally well for diesel but this was a very sudden failure while running with no knocks or bangs., so my money is on camshaft, but not a known weak point as far as I am aware, but good news is I have a spare, don't I always, Rick

[solarman216]

Originally Posted by Paff

How is it timed? Can that slip/go out?

big heavy gears, Rick

[Paff]

Originally Posted by solarman216

big heavy gears, Rick

Just a stab in the dark

[jims-terrano]

Are you sure decompresses are working correctly?

That's what sprung to my mind.

[solarman216]

yes bear in mind the motor started fine and then with a little woff stopped, can only be cam broke, Rick

[AlexD333]

Originally Posted by solarman216

yes bear in mind the motor started fine and then with a little woff stopped, can only be cam broke, Rick

I thought you said in your first post in cant possibly be? But then again, if anyone knows about them it will be you. I wanna find out what this is I'm interested!! I have seen these generators, they are mahoosive!!

[solarman216]

pulled the heads today, on first glance nothing abnormal, turned it over by hand and all happens in the correct sequence, so popped the valves out, the exhausts are well worn and uneven such that the seat on about a quarter way round is so wide, and pitted that if you turn the valve in the head it does not seat at all, now both valves are the same and they both have not rotated for years or they could not have worn this way, so why did they both decide to rotate and jamb open at exactly the same time, has to be millions to one, any way easy fix, I have some new valves about somewhere when I clean the heads up I will take some pics but far too dirty for that now and we are off out for dinner, Rick