95 Disco V8, no compression on No4

[procrastination inc]

Sudden miss fire noted when I started the car yesterday morning. No back firing, just rough idle.

Found some cracked connectors on a few plug leads, replaced, no better. Removed dizzy cap and cleaned, no better.

Removed plugs in drivers side bank and noticed no4(?) plug colour different.

Compression tested theses 4, 9.5 on all except the odd plug coloured one. Almost zero on that..

I'm guessing a sudden failure like that on start up is likely to be a stuck valve. I'll pull the cover tomorrow and check.

any other ideas?

[DEFENDERZOOK]

did you do a wet and dry compression test........?


it seems very unlikely to be a piston though........so i would say youve found the problem......

[procrastination inc]

rocker cover off, nothing obvious.

maybe a lifter has stuck and is holding a valve open.

Tomorrow, I'll chop up a sparkplug to make a compressed air fitting, pull the rockers off and see if it leaks out the exhaust or inlet then. If not, maybe just a new set of lifters will do the trick.

If it still leaks, the motor is coming out

[Tank]

Sudden miss fire noted when I started the car yesterday morning. No back firing, just rough idle.

Found some cracked connectors on a few plug leads, replaced, no better. Removed dizzy cap and cleaned, no better.

Removed plugs in drivers side bank and noticed no4(?) plug colour different.

Compression tested theses 4, 9.5 on all except the odd plug coloured one. Almost zero on that..

I'm guessing a sudden failure like that on start up is likely to be a stuck valve. I'll pull the cover tomorrow and check.

any other ideas?
You may have a crook valve or valve seat, do you have a vacuum tuning gauge, hook it up to a vacuum source, it should tell you if it is a valve causing the problem, Regards Frank.

[discowhite]

run the engine with the rocker cover off, that will tell you, by looking at the valves, if the valve train is at least opperating.
if it is it can be cracked/broken valve, cracked/broken piston (although this would make a racket, or at least you will have alot of blow by coming out the dipstick:D)

cheers phil