What does "No compression" mean?
Programbo
week as if one of the cylinders was missing. I changed all the plugs
and wires and cap/rotor and that fixed nothing. I was thinking maybe
an injector wasn`t working and turned the Jeep on and unplugged each
injector one at a time. Unplugging 4 of them made the engine start to
die off right away but the #2 and #3 injectors didn`t seem to change
anything when I unplugged them. So I figured those injectors were dead
and replaced them. No change again. Still running really rough. (I
know it was stupid wasting money but I really needed to try and get it
running as I had a trip down the highway I had to take on the
weekend.) I finally got tired of messing with it and took it to a
repair shop and the guy there called and told me, "There`s no
compression in those two cylinders." To make a long story short I just
told him to leave it alone and I`d come pick it up. But today I was
off work and went out to mess with it and I unplugged and removed the
2 spark plugs for those 2 cylinders (They were black with soot) and
when I fired the Jeep up there was a lot of air being pushed out of
the plug holes as the engine stroked. So I guess my question is: Isn`t
that compression? I`m trying to eliminate possible simple fixes before
junking this thing. Thanks for any input.
W????n S.
"Programbo" <progr...@aol.com> wrote in message
news:93f2e598-60c1-4e93...@z72g2000hsb.googlegroups.com...
So, with no plugs in it, the piston will push air. When the plug is
replaced, the rings/valves seal to create compression. I am willing to bet
there is still compression but very low.
Do you have a compression tester?
Put a teaspoon of motor oil in the plug hole and check compression again. If
it goes up it is rings, I believe. Stays the same, if it is valves. Did
mechanic do this test?
The soot is basically unburnt gases and blow by gathering on plug. I believe
that would be normal with a bad cylinder.
Could also be head gasket in which case you probably would have oil in
coolant as seen in radiator.
Could also be blown between cylinders which may explain the two being dead.
Mechanic should be able to narrow it down and recommend fix.
Let us know what gives!
Warren
Will Honea
Even a cylinder with visible air gaps between the piston and the cylinder
wall and valves stuck open will push a pretty fair amount of air out the
plug hole - but their may be no significant compression. The only way to
get meaningful data is to use a compression tester. You can probably
borrow one from a local parts house but they only cost something like $20.
Did they just give you a "no compression" or did they specify a number like
0 PSI? Having 2 adjacent cylinders go tits up at once while the others are
OK suggests the likelihood of a leak between the two cylinders or something
common like a leak to the outside from a common part. The head gasket
comes to mind - but that's going to be a sizable leak for a head gasket.
Get a compression test and report the actual numbers for each cylinder so
we can take a better WAG.
One thing to note: since the plugs are fouled black in the two bad
cylinders, we know they are actually firing and burning the fuel but they
are not burning it completely, which would be a fair indication of low
compression as the main problem. The fact that two adjacent cylinders are
affected would also tend to make me think that it may not be a catastrophic
problem - unless you've manages to crack a head or cylinder wall.
--
Will Honea
** Posted from http://www.teranews.com **
Jo Baggs
the rings are worn or the valve is bad, you can not take advantage of the
"compression" of the explosion in the cylinder. It will blow by the rings
or the valve and give you little or no power in that cylinder.
The air you hear coming out the spark plug hole is only a portion of the
compressed air the would otherwise be used to turn your crankshaft.
"Programbo" <progr...@aol.com> wrote in message
news:93f2e598-60c1-4e93...@z72g2000hsb.googlegroups.com...
** Posted from http://www.teranews.com **