F250 compression #s

[formula29]

I do not believe air leaking through the exhaust is a problem with the HF gauge.
Is that what you were getting at?

May need to check all of the cylinders with it.
I do not see where the gauge is a problem with just what you wrote.

I wonder since this VCT works off of oil pressure, what is the oil pressure at idle?

since you were reading +12 on one side and Rod said that is the one that is way off, it must be stuck maybe.
If a filter is plugged would / could it show up like this?

I have no clue about this problem, but this is interesting to me

Oil pressure was aprox 80psi ad idle, the problem with HF gauge was the second indicator gauge is broken, the needle doesn't move at all, I am more obsessed with figuring out where the problem lies than anything, things like this drive me nuts until I can figure it out, I actually enjoy repairing engines, just not when I pay for a good running engine.

[formula29]

I'm working on it, the pointer for tdc has not been reinstalled when they did the powerhead I assume, so without pulling the flywheel I am guessing it is close both, motors!. the problem with the gauge I bought is the 2nd gauge does not read at all, it is defective,

[rodbolt17]

look on your flywheel.
do you see the 3 index marks, one is going to have a grid with a TDC mark and marks for BTDC and ATDC.
the other two will simply be labeled TDC.

the one with the grid is the #1 cyl.

remember that motor,unlike a two stroke, has to rotate 720* to complete all 6 fire cycles.
means each piston comes to TDC twice in 720*.
once on compression stroke(all valves closed) once on ex stroke,valves still open.

[formula29]

If I cant figure it out I will be taking it back to the dealer, problem being its a 3 hr trip or they would already be there, I am going to spend some more time on it today, things like this really help you get familiar with your motor anyway! try to stay positive !

[rodbolt17]

do not worry about any cam mark
what your looking for is #1 at TDC on compression stroke.
so line up the flywheel index mark with the pointer.
its either going to be TDC compression or ex.
if its on the ex stroke rotate the flywheel 360 and then try.
from there simply run the index marks through the fireing order.
once #1 TDC compression stroke is found every 120* for the next 720* of rotation is going to bring the next piston up.
fireing order for that motor is a complex 1,2,3,4,5 and 6.

your flywheel should have 3 index marks numbered 1-3.

DO not worry about the cam maarks at this point.
the flywheel marks are not used in any cam timing operations.

[99yam40]

Guys I welcome all of the feedback at this point, after running this morning I did the static test on the oil con*****ers and they did the clicking thing, then I went out and bought a leak down tester, unfortunately I bought a harbor freight and it is a pos and does not work, with #1 on top dead center all the cam pointers were lined up and when I put air to the #1 cylinder I could hear it leaking through the exhaust, I rotated the crank another couple of degrees and the exhaust valves sealed, when I was looking at the intake valve timing earlier on the yds the port being advanced 12 and the starboard being retarded 2 degrees I ran the engine rpms up to see if they changed at all, they evened out both sides at I think +14 degrees at 2500 rpms. I think something is out of wack with the intake cam timing personally, I may pull the flywheel and try a new timing belt on one motor but will also buy a good leak down gauge to get a proper test, I have read the manual regarding the vct and how it works with some kind of pin holding it in place until oil pressure takes over? these powerheads were replaced several years ago, I wonder if the tech could have assembled something wrong back then and nobody ever checked compression? I had enough for today, back at it in the morning and thanks again for all the information.

I do not believe air leaking through the exhaust is a problem with the HF gauge.
Is that what you were getting at?

May need to check all of the cylinders with it.
I do not see where the gauge is a problem with just what you wrote.

I wonder since this VCT works off of oil pressure, what is the oil pressure at idle?

since you were reading +12 on one side and Rod said that is the one that is way off, it must be stuck maybe.
If a filter is plugged would / could it show up like this?

I have no clue about this problem, but this is interesting to me

[TownsendsFJR1300]

IMO, you may consider bringing them back and let them deal with it (then double check their work if its repaired). Seems like a headache that the dealer should have found and repaired before selling them....


But, if not, here's a good leak down tester I've been using for years. It seems very accurate and won't cost an arm and a leg.

.
.
https://www.otctools.com/products/cy...age-tester-kit

.

[formula29]

Guys I welcome all of the feedback at this point, after running this morning I did the static test on the oil con*****ers and they did the clicking thing, then I went out and bought a leak down tester, unfortunately I bought a harbor freight and it is a pos and does not work, with #1 on top dead center all the cam pointers were lined up and when I put air to the #1 cylinder I could hear it leaking through the exhaust, I rotated the crank another couple of degrees and the exhaust valves sealed, when I was looking at the intake valve timing earlier on the yds the port being advanced 12 and the starboard being retarded 2 degrees I ran the engine rpms up to see if they changed at all, they evened out both sides at I think +14 degrees at 2500 rpms. I think something is out of wack with the intake cam timing personally, I may pull the flywheel and try a new timing belt on one motor but will also buy a good leak down gauge to get a proper test, I have read the manual regarding the vct and how it works with some kind of pin holding it in place until oil pressure takes over? these powerheads were replaced several years ago, I wonder if the tech could have assembled something wrong back then and nobody ever checked compression? I had enough for today, back at it in the morning and thanks again for all the information.

[99yam40]

would the filter be the most likely

[rodbolt17]

the intake cams at idle typically bounce between about -2* and 2 *.
if one is at -2* and the other is at 12* that indicates a problem.

[99yam40]

in the posters 250 most likely he is going to find one bank that all the intake valves are leaking slightly due to a mispositioned intake cam.

however the industry standard of 20% highest to lowest would make the posters F250 a pass yet the above poster is most likely going to find mechanical issues.

either a cam is out of position or the mechanism is stuck or the OCV is stuck or the filter clogged.

I am sure this is the stuff the OP was looking for

[rodbolt17]

Boscoe
just cause I guess you don't like nor use the leakdown test its ok to make fun of it.
in the above example the engine had been passed by another tech.

all his compression numbers ran from a high of 185 to a low of 165.
well within the industry standards of 20% higest to lowest.
however I was tasked to do an engine survey for a customer prior to his purchase of the above motor.

I read the other shops numbers, they looked ok.

however 4 had intake valves leaking and 3 had excessive blowby past the rings.

this was found with the leakdown test.
I am 55 and have been doing leakdown tests since I was 15.

Yamaha DOES ask for the leakdown test results on blown or suspected blown 4 strokes.

the above customer tipped me well and backed out of the purchase.

I saved him a ton of money in a 15 min test of 8 cylinders.

I can do a leakdown test in about 1/2 the time of a compression test and it way more accurate.

the owner of the above engine says it runs great and he is going to run it.
I said arrriighht.

in the posters 250 most likely he is going to find one bank that all the intake valves are leaking slightly due to a mispositioned intake cam.

however the industry standard of 20% highest to lowest would make the posters F250 a pass yet the above poster is most likely going to find mechanical issues.

either a cam is out of position or the mechanism is stuck or the OCV is stuck or the filter clogged.

[boscoe99]

Yes. Do the leak down test. More correctly known as a differential pressure test.

Might want to do it three times just to be sure and average the readings. If each and every cylinder is not perfectly aligned with every other cylinder, great harm may come to the motor. Each cylinder ideally will have no more than one psi loss of pressure. Hard to get those pesky rings to make a perfect seal. If not within the one psi tolerance, at best it won't run as well as it should.

It will magically cure the motor of any and all ills.

Yamaha thinks so highly of the differential pressure test that they make no mention of it at all in their service manuals. I guess they assume that all will know that it has to be done (every six months would be a good schedule) as it will go a long way to ensure great engine life.

If the aluminum does not corrode away first.

[zenoahphobic]

I just ran the motors while watching the yds, it showed port cam intake timing at +12 degrees and the starboard was showing -2 degrees does this look right rodbolt?

Now that is telling.
Previously as you were not given an answer, I would have said as both appear the same in compression tests that both suffer maybe something like carbon build up on the starboard(?) valves due to the way they have been used.

But it is also logical to assume that all maintenance (adjustments, replacements) would have been done at the same time and by the same person. Human error maybe, or far more remotely, a faulty batch of parts.

Or maybe simply the engines have been neglected and have developed there own individual problems (return to supplier).

[rodbolt17]

no, something is not right.
they should run within a few degrees of each other.
do the leakdown test.