Checking Compression - What did I do wrong?

[Estrogen Hostage]

Last night I was doing a compression check. The cab is off the truck, and both valve covers were off. The injectors were pulled out, and the oil drained from the cylinders. I cranked it over several timed to make sure the cylinders were clear.

So, I installed injectors on one bank of the engine, and pulled all four glow plugs. The second cylinder I got to shot oil out the other side of the engine with enough force to shoot the other valve cover off on the floor (it was just sitting there not bolted in). Why did cranking it over push oil into that other cylinder? Do you guys think I hurt anything?

 

[907DAVE]

Did you crank it with the injectors out?

 

[Tom S]

As soon as you cranked it without injectors installed the hpop put oil into those cylinders.

 

[Estrogen Hostage]

This was more oil than would come from the HPOP, and I would have assumed it drained out.

I've had the injectors out for a month. I went to check compression on the pas. side, so I removed the glow plugs and reinstalled the injectors. The other bank of cylinders had glow plugs but no injectors. One by one I checked compression. The second one I tried pushed the oil out from a cylinder on the other side of the engine.

 

[woodduck97]

If the injectors were out and you cranked it the HPOP pushed oil into the cylinders.

 

[neverkickn]

This was more oil than would come from the HPOP, and I would have assumed it drained out.

I've had the injectors out for a month. I went to check compression on the pas. side, so I removed the glow plugs and reinstalled the injectors. The other bank of cylinders had glow plugs but no injectors. One by one I checked compression. The second one I tried pushed the oil out from a cylinder on the other side of the engine.

You might think but it doesn't take much oil in the cyinder to shoot out of the gp hole with enough force to blow a loose valve gover off.

 

[95powersmoker]

You need to have all injectors in... Then remove glow plugs and test your compression... They must be seated and torqued... And get all the oil/fuel out of the cylinders before testing or it will mess with your numbers..

 

[mandkole]

yup-- the test should have been run before any injs were removed.

The issue you'll have now is that there is residual oil in the cyls that will help the sealing and help an otherwise bad cyl. If you want the best info, I'd button the whole thing back up, get it running and cleaned out, then tear it back down and only pull the glowplugs.

 

[golfer]

have to get it running again...to burn off any fuel/oil in the cyls...then pull GP's and retest compression.

 

[Estrogen Hostage]

That's not happening any time soon....cab is off. I cranked it over for a while before checking compression - this was just informational readings, I wasn't worried about anything. I guess I'll throw it all back together and enjoy it!