240psi compression

[BIGMIKE]

I've searched and searched and I'm pretty sure I know the answer but thought I'd run it by you guys with more knowledge about it than me.
So my major is still a pig to start from cold and has to crank over and slowly coughs and splutters into life then starts fine when it's hot, but what I've found is cylinder 1 is stone cold and doesn't fire when cold, I swapped the injectors over just in case even though they've been reconditioned and it made no difference so eventually I've got round to making a compression adapter from an old injector and I've found cylinder 1 is down to 240 and jumps up to over 400 with a bit of oil and the other 3 are all 330-340psi so is 240 low enough for that cylinder to not fire at all and cause it to be such a pig to start from cold as I've always been told majors are good cold starters?
Mike

[Pavel]

The oil test is designed to temporarily seal the piston rings rather than p/rings and valves combined. Your test would tend to indicate that the piston rings on that cylinder are broken -- or the piston is holed, since the other cylinder readings are good.
Diesel Majors are good starters provided the rings and valves are in reasonably good nick.

Pavel

[BIGMIKE]

I know the head is good as I rebuilt it last year so I know it's the rings on number 1 causing the lower compression my question was, is 240psi low enough for that cylinder not to fire at all and would you expect the other 3 all being 330-340 enough to make it Start better than it does???

[Pavel]

As a diesel engine is 'compression ignition' it is important that those compression's remain highish -- as I'm surer you are aware. Because cyls. 2,3 & 4 are down 15% I would suggest that with no. 1 being 40% below par, in total that is enough to cause difficult starting -- especially as you have cold weather at present. You could, of course, use a can of ether as a stop gap; but if my diesel had that loss of compression on one cylinder I would most definitely investigate further.

You mentioned that last year you overhauled the head; so questions:
Was that in the summer months when the induction air was warmer; and was starting it acceptable?
If so did difficult starting only occur as the weather got colder?
I ask because it crosses my mind that the fault could possibly be a bad sealing head gasket -- although the oil test should have eliminated that also.
You could also try removing the rocker cover breather pipe whilst the engine is running to see how much oily vapour is pumped out -- there should be very little.

Pavel.