Compression Readings

[NTIGUY]

I did a compression check on this truck and here are the readings. I want to see what you guys think before I start pulling parts.. Its a 2003 Ford F350 with a 7.3.

#1)300
#2)400
#3)300
#4)300
#5)360
#6)300
#7)360
#8)120

Thanks much

[ianstew]

#8 stanky.... 300 and up good 120 bad juju

[NoRalPh]

Squirt some motor oil in # 8 and try it again to see how much it comes up (could be valve/valvetrain trouble)

[NTIGUY]

What about with 500xxx miles on it? And I am going to do a leakdown test on it tomorrow and see what is going on.. But I will let you all know what I find.

[NTIGUY]

Well further diagnose with a leakdown test shows that the loss of compression is coming from either the piston or the rings. I am pulling engine out today and I will let y'all know what I find.

[NTIGUY]

Well got the engine out, only took a little over 5 hours. Got the head off and that cylinder is cleaner that the rest of them, and the exhaust valve for #8 is clean. And the injector bore where the injector sits down has some carbon in it. Gonna bring the whole thing to the machine shop and have it hot tanked, magnafluxed, line bored and honed, cylinders bored and honed. Then get it back together. Should be good for another 500,000 or so miles.

[NCHornet]

Man 5 hours is good time. I was going to warn you about getting a beefy hoist and engine stand, but looks like I am to late, lol!!!

[NTIGUY]

Found that #8 2nd compression ring was stuck.

[BIG JOE]

Originally Posted by NTIGUY

Found that #8 2nd compression ring was stuck.

Have you checked your battery cables?

[NTIGUY]

Yes I have checked my battery cables, but are they really linked to compression rings? I didnt think so, I tore the engine down and didnt find any wires running to the rings. But is my underlying problem battery cables/connections?