F250 compression #s

[99yam40]

I wonder if the cam timing Degrees on YDS changed also?

Are the sprockets suppose to be the same on both sides in the parts breakdown?

edit
not sure if I looked at the correct f250 breakdown but the driven gear and the pully lists 2 each, so they should be the same is my thoughts

[formula29]

Rodbolt is answer to holding the throttle open, you simply push in the neutral detent in the shifter and open the throttle, I verified the plate opened fully. prior to this I tested with throttle closed and got the same numbers believe it or not, I my first attempt I didn't know if you could open the throttle plate manually and I didn't want to damage it so I ran the test with it closed, I came up with the funky numbers so I was going to pull the throttle body and re test, after I removed the upper housing I figured I would see if the throttle would open up with the engine not running but key on and wide open throttle and it does.

[formula29]

I wonder if the cam timing Degrees on YDS changed also?

Are the sprockets suppose to be the same on both sides in the parts breakdown?

yes, both sprockets are the same on the parts diagram, one of mine is wrong, I compared the cam dowel inside it and they look to be about 1/16 farther apart

[zenoahphobic]

yes, both sprockets are the same on the parts diagram, one of mine is wrong, I compared the cam dowel inside it and they look to be about 1/16 farther apart

Well there you have it. Cam sprocket but which one?
Has it been agreed that the correct compression is 195psi?

[zenoahphobic]

Sorry to bring up leakdown tester again. Reference to it continued in regard to 0%. It is important to know our test equipment because we rely on them to not make wrong decisions that can lead to unnecessary costly maintenance.

Simply, when one sees the second gauge reading 100 psi the leak is not necessarily zero, it is more likely that there is a leak that is equal in area to the orifice between the gauges. We conveniently set the pressure to 100 so that we convince ourselves (not me though) that a lesser reading on the second gauge is a percentage loss. This is BS of course.

If I were a master mechanic, not only would I not use analogue dial gauges but transducers, but have an adjustable (graduated) orifice (sorry I don't wish to appear to have an obsession with these). I would not then question a "zero percentage", and make a statement that I would question my test equipment only if all readings are "zero percentage".

You can do 3 things:
1. ignore, no problem here,
2. turn off your compressor and shut off valve and watch the pressure drop which will tell you something. Just like a compression gauge(s) with the one way valve removed, or
3. use your tester correctly and screw the orifice down until the second gauge actually begins to drop! indicating the actual leak.

[rodbolt17]

if I tested 6 cyl's 4 were 5% or less and two indicated 0 then I would figure the leakage is to small for my equipment to measure and all is good in the hood and continue on.
this stuff aint hard if you don't over think it.
don't get hung up on stupid stuff.
remember that motor is actually 6 little motors that share a common crank and a common air intake.
if the compression test shows 195 on one bank and 170 on the other its FREAKING trying to tell ya sumptin ya think?

the next clue, the freaking cam timing IS NOT where it should be.
the cams should pretty much stay within a few degrees of each other at all times.

intake cam timing WILL affect compression.
it is NOT designed to have unequal compression unlike some 2 strokes of years past.

the compression test indicated a POTENTIAL [problem.
that needs to be looked at via a LEAKDOWN test.

now if it was your 100 bucks an hour,and its faster to do a leakage vs compression, would you like to pay for BOTH tests or just the more accurate of the two?

so that leaves did someone use the wrong parts that physically fit?
did someone reinstall a cam incorrectly?
did someone improperly shim the intake cam during a repair?

but something is wrong and its time to follow a logical rabbit trail.

not all throttles will open at just key on.
then you have to disable BOTH spark AND fuel.

[formula29]

Since my problem has been solved I will oblige you here, although my HF home made gauge did hold 100 psi on the output side I could not hear any leakage through the intake runners or exhaust, when I removed the oil filler cap I could hear a slight air flow, probably a few psi that my gauge was not showing, I failed to mention it because we know where that would have went, I knew that the few psi that was leaking past the rings was not the problem I was chasing. In my case a simple compression tester was the first line tool in determining if there is a problem, then we move on to a differential test to further diagnose, there are multiple ways to go about doing things, I like to listen to all ideas and figure out what makes sense for me, even with the aggravation of the differential test experts, in the end rodbolt confirmed my intake timing was off and was not right, and that helped me to switch direction to the port bank being the problem, so it all worked out, thank you to everyone that participated in this thread!

[formula29]

if I tested 6 cyl's 4 were 5% or less and two indicated 0 then I would figure the leakage is to small for my equipment to measure and all is good in the hood and continue on.
this stuff aint hard if you don't over think it.
don't get hung up on stupid stuff.
remember that motor is actually 6 little motors that share a common crank and a common air intake.
if the compression test shows 195 on one bank and 170 on the other its FREAKING trying to tell ya sumptin ya think?

the next clue, the freaking cam timing IS NOT where it should be.
the cams should pretty much stay within a few degrees of each other at all times.

intake cam timing WILL affect compression.
it is NOT designed to have unequal compression unlike some 2 strokes of years past.

the compression test indicated a POTENTIAL [problem.
that needs to be looked at via a LEAKDOWN test.

now if it was your 100 bucks an hour,and its faster to do a leakage vs compression, would you like to pay for BOTH tests or just the more accurate of the two?

so that leaves did someone use the wrong parts that physically fit?
did someone reinstall a cam incorrectly?
did someone improperly shim the intake cam during a repair?

but something is wrong and its time to follow a logical rabbit trail.

not all throttles will open at just key on.
then you have to disable BOTH spark AND fuel.

Rodbolt, did you catch the part where I switched vct's from port to starboard and the compression #s reversed? I have two different vct's,, and on compression test I do remove the kill switch, however I do not disable the fuel,

[zenoahphobic]

Point taken that too small to worry about, and quicker to do leakdown than compression test.

But I thought we had determined the leakdown test on this engine tells us nothing, so would you have then done a compression test? I infer you would not have! As the engine runs fine you probably would have told the customer the engine is fine! Logically you would not have had a reason to suspect anything wrong with the cam timing!

Sorry I see a little flaw following your postings, that's all.

Sorry referring to Rodbolt's last post.

[formula29]

Point taken that too small to worry about, and quicker to do leakdown than compression test.

But I thought we had determined the leakdown test on this engine tells us nothing, so would you have then done a compression test? I infer you would not have! As the engine runs fine you probably would have told the customer the engine is fine! Logically you would not have had a reason to suspect anything wrong with the cam timing!

Sorry I see a little flaw following your postings, that's all.

That is a valid point, a leak down would have not shown the compression difference in my case, but what I just went through should have never happened

[zenoahphobic]

Since my problem has been solved I will oblige you here, although my HF home made gauge did hold 100 psi on the output side I could not hear any leakage through the intake runners or exhaust, when I removed the oil filler cap I could hear a slight air flow, probably a few psi that my gauge was not showing, I failed to mention it because we know where that would have went, I knew that the few psi that was leaking past the rings was not the problem I was chasing. In my case a simple compression tester was the first line tool in determining if there is a problem, then we move on to a differential test to further diagnose, there are multiple ways to go about doing things, I like to listen to all ideas and figure out what makes sense for me, even with the aggravation of the differential test experts, in the end rodbolt confirmed my intake timing was off and was not right, and that helped me to switch direction to the port bank being the problem, so it all worked out, thank you to everyone that participated in this thread!

Formula 29 I think you determined your intake timing was wrong. You haven't told us which one was wrong! the 170 or the195 one?

[formula29]

I am going to have to say the 170 psi is the correct range since that bank had the correct timing, the bank that had 195 psi had the 12 degree advance at idle, it made my morning when I switched the vct with each other and pulled another compression test and the numbers reversed, now to round up a couple used vct's, the dealer was not very interested in talking to me,

[99yam40]

I still do not understand how/why someone would put one wrong VCT sprocket on the same side of both motors?
where did these come from?
they should not have come from the motors they took apart to repair.

A big question from me is, does the YDS show the cam timing problem the same on the other side now? just to verify that the timing problem followed the sprocket?
it should have if that is truly the problem


I am guessing you will be contacting the shop that sold you these motors to have the proper sprockets/parts replaced

sorry i missed your last post on them not interested in talking to you.
too bad it would be intresting to find out how this happened

[boscoe99]

If the compression test is the proverbial teat on a boar hog, and the leak down test is the definitive be all end all test, how is it that the compression test showed a problem whereas the leak down test indicated there was no problem at all?

I be confused.

Mr. Rodbolt - We await your advice.

[99yam40]

computer showed a problem, but someone( most of us) did not pay attention or did not know it was a problem.
Or what kind of problem it was
I have a hard time believing they did the same thing to both motors without it being on purpose