Where does it get the air to compress? Pulls a vacuum when the piston goes
down before the compression stroke.

wrote in message
ups.com...


Bill McKee wrote:
. And my daughters Explorer broke the intake rocker and
zero compression reading.

How? Intake valve ALWAYS closed that way. So, when the piston comes up
on the compression stroke, both valves would be closed JUST EXACTLY
like they would be if the intake rocker wasn't broke.

ok heres the story,

Pulled the valve cover. Value is moving up and down.
cranked the motor until the valves were closed, blew compressed air in spark
plug hole, no air came out the exhaust or intake.
yanked the head off, no hole in cylinder (that I can see), head gasket look
ok from what I could tell

Any suggestions?

"nate" wrote in message
. ..
I read each post and appreciate everyone taking the time to reply. I'm
going to tear into it this weekend and will post the results.


"Capt John" wrote in message
oups.com...
I agree with the guy's that indicated it's an intake valve issue. Pull
the valve covers first, see if the rocker or push rod is the problem. I
have seen cases where the rocker stud pulled out, but that would keep
the valve closed. The valve could be stuck open, in which case the
rocker will be real loose.

First, I hope you were correct in your original test resulting in "zero"comp
in one cyl. If you don't see anything unusual, looking at the top of the
"bad" cyl, compared to the others, look closely at the valves at the seat
area. You could have some burned pitted area there. You will need a valve
spring compressor which you can buy for $20-30 bucks at the local ap store
or possibly rent. When you "blew comp. air in spark plug hole", did you
seal the air source (with a rubber or threaded fitting to the hole where you
had a "sealed" system and heard no air leaking, at 100-150psi? Or, did you
just blow air into the hole and hold your hand over the exhaust/intake?

I hate to say it but if you can't see anything "unusual" with the
valve/seat, or the gasket or the top of the piston, or, some marking/scoring
on the cyl wall w/piston at bottom, you may have mis-read the gauge or not
seated it properly on that cyl. I think a week spring/sticking valve was
already covered and you need to remove it to check (along with the seat). I
would say there's one other possibility but it would have to affect all
cylinders. That is a slipped chain on the camshaft, which would change the
valve timing, possibly resulting in the two conditions you
mentioned--backfiring and zero compression--but would affect all cylinders
equally.
"t" wrote in message
.. .
ok heres the story,

Pulled the valve cover. Value is moving up and down.
cranked the motor until the valves were closed, blew compressed air in
spark
plug hole, no air came out the exhaust or intake.
yanked the head off, no hole in cylinder (that I can see), head gasket
look
ok from what I could tell

Any suggestions?

"nate" wrote in message
. ..
I read each post and appreciate everyone taking the time to reply. I'm
going to tear into it this weekend and will post the results.


"Capt John" wrote in message
oups.com...
I agree with the guy's that indicated it's an intake valve issue. Pull
the valve covers first, see if the rocker or push rod is the problem. I
have seen cases where the rocker stud pulled out, but that would keep
the valve closed. The valve could be stuck open, in which case the
rocker will be real loose.

Problem found!

After taking the head off. I poured water into all the intake ports. They
all held water except for the valve in question. The water poured right
out. I took it to the machine shop to have the valve or head replaced.

"t" wrote in message
.. .
ok heres the story,

Pulled the valve cover. Value is moving up and down.
cranked the motor until the valves were closed, blew compressed air in
spark plug hole, no air came out the exhaust or intake.
yanked the head off, no hole in cylinder (that I can see), head gasket
look ok from what I could tell

Any suggestions?

"nate" wrote in message
. ..
I read each post and appreciate everyone taking the time to reply. I'm
going to tear into it this weekend and will post the results.


"Capt John" wrote in message
oups.com...
I agree with the guy's that indicated it's an intake valve issue. Pull
the valve covers first, see if the rocker or push rod is the problem. I
have seen cases where the rocker stud pulled out, but that would keep
the valve closed. The valve could be stuck open, in which case the
rocker will be real loose.