Compression Test Results

[ORCoaster]

And a simple check on the valve clearances would be good to do.  A few of mine were way off somehow.  One like no clearance. 

[libbydiesel]

Yes, that's what I've been trying to say.  The mechanically operated valves wear to being tighter and will eventually lower compression especially when the engine is cold.  Hydraulic lifters can similarly cause compression test issues if they are not operating properly or have been allowed to bleed down prior to the test. 

[ORCoaster]

Before even considering pulling the head, make sure the valves are opening far enough. 

I followed it but didn't think he would know how to determine if they were indeed opening far enough.  So I put it in different terms. 

[zolorin]

OR Coaster, you are the guy with the best idea

So I have tested the valve clearances and 

Lets just say there was about 0.20 ++ mm of excess valve clearance (again done cold)

The readings were
0.025 inch for all exhaust valves (nominal is .014 to .018)
intake
1 -- .019
2 -- .016
3 -- .014
4 -- .020
with nominal at .006 to .010

Based on Bentley

So very low compression numbers could have been a result of the cam having a smaller window to open and close the valves,  Hence a big power drain at higher rpm (say at 70 mph).

So will do get the shims and go

[air-cooled or diesel]

Once you have these readings you could squirt about a tablespoon of oil in the top then place the adapter in the injector hole and try again.  If rings are the issue you normally will see an increase in pressure.  Try it and see what you get.  I have one cylinder that is bad and oil gives me 80-100 lbs more on a stone cold engine.[/quote]

Did you do the test with the engine at normal operating temp?

Be careful with that "wet test"... these engines run on oil.

this test while being real good for reading ring sealing, especially while engine is at normal temps; oil will fire. while engine is dead cold you shouldnt get firing, but cylinder is live and has a fuel that it can burn. dont have your helper holding tester while doing this. its possible to lose your tester; if cyl fires(done cold)

[ORCoaster]

Actually I have to pass credit on the valve clearance to Libby.  I thought oil would be the check for ring wear and just restated the clearance as another possible before you started to tear the head off.  Maybe no need to do that?  Reset the clearance proper and retest cold.  Report numbers and then try oil and retest. 

Cautions on the oil kicking the engine over.  If you pull all four injectors I doubt this will be a problem. That is generally how I do it.  Get the injectors and lines out of the way and then have room and easy spin of engine.  I have never had one fire off the oil when completely cold and no glow plug juice.  I pull my pimp wires but anyone with stock setup could remove the fuse on the firewall.  I also pull the lead from the IP so diesel isn't squirting all over from that.

[zolorin]

I always take the plugs (gas) or injectors (diesel) out before doing the compression test.  Extra pressure on the other 3 cylinders slows down the rotation speed and makes the reading numbers low.  Learned that from my datsun days.  Anyway will unbolt the glow plug harness too.  Dont want to have an explosion in my garage.

Oil fires are hard to put out

[tyb525]

Wouldn't unhooking the stop solenoid prevent fuel from coming out of the injection pump?

[TylerDurden]

Wouldn't unhooking the stop solenoid prevent fuel from coming out of the injection pump?

Ja... the IP spits fuel, unless the stop wire is off. (Messy; and fuel is bad for the hoses.)

The concern is for adding oil into a cylinder for a wet-test.