Compression Figures?

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intresting, mine seems to have lost some of its power and has developed a knocking noise under load. replace the lift pump as i thought it was that but now am thionking it might be something more serious.
 
intresting, mine seems to have lost some of its power and has developed a knocking noise under load. replace the lift pump as i thought it was that but now am thionking it might be something more serious.

A knocking sound immediately makes me think of the worst case scenario (big end bearings) but it could be quite a number of things. I'd be tempted to take the rocker cover off and then run the engine to check that none of the rocker arms or the push rods have snapped, it could even be a valve spring that's broken. It'll spew oil out all over the place though so bear that in mind before you start the engine. If there's nothing obvious up there, try slackening off your first injector pipe and see if the noise stops. If it persists, tighten it back up and then proceed to the next injector. It could also be a few other things such as the oil pump drive shaft or the big end bearings but try and rule out all the other potential problems first. Is the turbo spinning properly and how much play is there in the compressor spindle? It should wiggle very slightly in all directions. Does it become louder when revved or does it die down?

-Pos
 
not sure where the disco bloke gets his figures from ?

i'd be expecting something over 400psi - but it's the relative results you need to consider, LR recommend not more than 70 psi difference between any cylinder


I just took atmospheric pressure and multiplied it by 19.5 which in theory is correct, it gives you a basic pressure to work with, although I agree it would be higher.
 
It is possible that there will be some leakage from the valve seals, but they're easily replaced.

NO, the valve against the valve seat creates the seal, the valve stem seal is NOT sealing the cylinder in any way shape or form.
 
NO, the valve against the valve seat creates the seal, the valve stem seal is NOT sealing the cylinder in any way shape or form.

Hence the reason for valve lapping / seating tools! :doh: What's the purpose of the valve seal then? Is that to stop oil running down onto the top of the valve, which would obviously collate when the engine is off, ready to drip straight into the cylinder?

-Pos
 
interesting, mine seems to have lost some of its power and has developed a knocking noise under load. replace the lift pump as i thought it was that but now am thinking it might be something more serious.

I would not jump to the worst case scenario yet, knocking can be caused by lots of things from dodgy injectors, HGF, fueling issues...

These are all MUCH cheaper and easier to fix than jumping straight to a rebuild.
 
Hence the reason for valve lapping / seating tools! :doh: What's the purpose of the valve seal then? Is that to stop oil running down onto the top of the valve, which would obviously COLLECT when the engine is off, ready to drip straight into the cylinder?

-Pos

Yes.

Remember what the valve stem runs through, the inlet and outlet ports, so the seals the manifold vacuum and exhaust pressure from the crankcase and reduces oil being sucked/leaking down below to a thin film (just enough to lubricate it at the seal).
 
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