Low compresssion on all cylinders ??

[BorJansson]

I have just gone trough an 6,5l engine, new heads, grinded valves, bearings, piston rings etc.etc.
I got the idea to make a compression test before I lifted engine in.
Lucky me !
All cylinder have 200 psi ?
I checked the meter and it's OK.
I have made some mistake somewhere, but what, camshaft and timing ?
I'll start to take it apart day after tomorrow.
Somebody with a good suggestion ?

I wish You a Happy New Year.

[DmaxMaverick]

Any compression test done on the engine that's not up to or near operating temperature will not be reliable. If the engine was cold, and all the compression values were near the same, it's probably OK. If this is a new/rebuilt engine with new rings, it's likely normal, especially if the cylinders/rings are dry. DO NOT try to do a "wet" cylinder compression test on this engine. Engine oil you may use to "wet" the cylinders is FUEL to a Diesel engine, and any cylinders with compression may fire.

[phantom309]

. DO NOT try to do a "wet" cylinder compression test on this engine. Engine oil you may use to "wet" the cylinders is FUEL to a Diesel engine, and any cylinders with compression may fire.

No thats funny right there,. a 6.5 IDI firing on just a squirt of oil?

If it fires once,. it'll do what?


200 psi on a new dry motor wouldn't bother me,..

[DmaxMaverick]

No thats funny right there,. a 6.5 IDI firing on just a squirt of oil?

If it fires once,. it'll do what?


200 psi on a new dry motor wouldn't bother me,..

Come on......

If it fires once, it will fire on ALL wet cylinders. In my experience (my luck), the one that fires will be the last one, and it will run away until all the oil is consumed. Until you've experience it, you won't understand. SURPRISE!!!! (ring your ears, right before having to change your shorts). It's a Diesel, and runs on OIL. It only takes one to "hit", then the rest follow. IDI means nothing with 21:1 compression engine with all cylinders charged. Very unlikely on a cold engine, but it CAN happen, and has. Just ask me!

[BorJansson]

Thank You for putting me on the right track.
I made a compression test on a spare motor that I have.
Same conditions, room temperature.
Abt. same readings, 210 - 240 psi.
I will lift the engine in and hope for the best.
Case is closed !

Have a nice day.

[phantom309]

Perhaps you think i got off the bus yesterday?

I bought a 1969 8v71 cabover freightliner with a spicer 4x4 2stick trans in it in 1977,. it was the first diesel i learned to take apart and fix,. on a regular basis too,..we haul the heaviest weights here in ontario without a gazillion axles,so being young and enthusiastic and determined to show my skills as a trucker, i broke it quite often,.:o
I paid that truck off the first winter hauling logs out of the bush,.back when the dot weren't like flies, and every cop wasn't a wanna be dot too,. and the only scale around was at the mill,..so we'd sneak a few extra pounds on,.;)

The guy said he had it on a stand,.it,s a new engine,. it,s going to run away? :eek:

Nah!!!,. your flair for the dramatics is entertaining tho,. :rolleyes:

I had to smother a 6-71 that had a stuck injector,.in a mid 70's gmc 9500, was exciting standing next to it whacking the air flapper that was seized of course,..while it was wailing away,. an older unit with no clutch fan,. so my biggest concern was the propelor coming apart, add in the fact i had hair in those days,and the wind was pretty strong from the fan, 9500's had very short hoods,.and 2 stroke jimmy's sound pretty impressive at 4000 rpm or so,..

As for experience,. well time grants that to all of us, but i,ve known techs that have worked in dealerships for many years,. they get really good at R+Ring new parts, and in warm dry climate parts of the continent, it just isn't the same as the experience gained by working in the rust belt,. and oft times fabricating, or repairing/refurbishing parts that financially couldn't be bought, so fix what ya got kinda thing,.and these same factory experienced 'techs' are way out of their depth and comfort zone patching used equipment. The Macgyver gene gets developed more when it,s your own stuff, and you're poor,.

So,. maybe if he does the compression test 1 hole at a time,. with glow plugs out of the other 7 holes?,. he might limit the "runaway" time considerably?:D

Funny how every 6.5 i,ve ever had to work with,. if the glow plugs aren't working,.. it doesn't want to fire!!,. and that is with good compression and atomized diesel being squirted in,..:D

Guess mebbe things are different in sunny california,..?? :)

Anyhoo,. keep your sock on,..watch out for runaway 6.5's,.it's all good.:D

Nick

[jdd75]

I was About 18 when I took my diesel course.
The shop had 5 or 6 dead engines used for training.
Our instructor gave two of use the job to see if we
could get them running.
One was a Lister single cylinder engine.
They were metric and had been taken apart so often
that standard SAE bolts had gotten it the mix.
We got it started bur the bolts didn't hold the pump on
As it was slowing down we feed it with the oily sawdust
directly in to the the intake and it kept running.
The instructor was quite impressed and laughing.
Then the Sh///t hit the fan.
The Principal came in madder than a hatter.
Seems when they put the exhaust stack up they only
went 3 floors in a 5 story building.
The stack ended just below the Stenography class.
The black smoke filled their class room to the point
that they could not see.

[ginger743]

Feed the runaway intake with a CO2 fire extinguisher, that should put out the , " fire " :>)

Jerry

[arveetek]

I had to smother a 6-71 that had a stuck injector,.in a mid 70's gmc 9500, was exciting standing next to it whacking the air flapper that was seized of course,..while it was wailing away,... 2 stroke jimmy's sound pretty impressive at 4000 rpm or so,..


I, too, have got to enjoy a runaway 671 for just the same reason. Apparently, the old Detroits are notorious for sticking fuel racks.

My dad has a 671 in an old project truck. It's currently just a chassis with no body. We decided to fire up the old Detroit one day since it had been sitting a while. It fired up all right, and kept right on going!! Dad grabbed the rubber fuel and tried to pinch it down, which slowed the engine down, while I found a block of wood to block off the intake. Very exciting there for a while. I think I might have needed new shorts after that....

Back to the original poster, I believe Greg is just doing his best to educate everyone to practice the best mechanical safety procedures possible. Perhaps the OP doesn't have the knowledge and experience that some of the rest of us do. Yes, it's very unlikely that a 6.5L would fire in such a situation, but it is possible. Better to know that going forward than to learn it the hard way and perhaps have to change your shorts, or worse, suffer personal injury.

Casey

[arveetek]

I was About 18 when I took my diesel course.
The shop had 5 or 6 dead engines used for training.
Our instructor gave two of use the job to see if we
could get them running.
One was a Lister single cylinder engine.
They were metric and had been taken apart so often
that standard SAE bolts had gotten it the mix.
We got it started bur the bolts didn't hold the pump on
As it was slowing down we feed it with the oily sawdust
directly in to the the intake and it kept running.
The instructor was quite impressed and laughing.
Then the Sh///t hit the fan.
The Principal came in madder than a hatter.
Seems when they put the exhaust stack up they only
went 3 floors in a 5 story building.
The stack ended just below the Stenography class.
The black smoke filled their class room to the point
that they could not see.

Great story!!!

Casey