Compression Test Procedure ?

[buddy]

So below is the defined compression test procedure...the defined tools arent important, but my only question is what is the cover for the air intake for? Are you supposed to block off the intake?

•Tools Required
•J 29664 Cover Set
•J 26999 Compression Gauge
•J 26999-10 Compression Gauge Adapter
•Or equivalents
1.Remove the air cleaner. Cover the opening in the intake manifold with J 29664.
2.Disconnect the pink wire from the fuel solenoid terminal of the injection pump.
3.Disconnect the wires from the glow plugs.
4.Remove all of the glow plugs.
5.Screw the J 26999-10 into the glow plug hole of the cylinder that is being checked. Connect the J 26999-10 to the J 26999.
6.Make sure that the batteries are fully charged. The engine should be at normal operating temperature.
7.Crank the engine. Allow the engine to turn over six times (six "puffs") per cylinder. CAUTION: Do not add oil to any cylinder during a compression test as extensive engine damage may result.
8.Take the compression test at each cylinder and record the readings.
9.The lowest reading cylinder should not be less than 80 percent of the highest reading cylinder. No cylinder should read less than 2625 kPa (380 psi).
•Normal: The compression builds up quickly and evenly to the specified compression on each cylinder. The reading should be within the 2625-2760 kPa (380-400 psi) range .
•Leaking: The compression is low on the first stroke. The compression builds up on the following strokes but does not reach the normal level.

 

[96 OILBURNER]

The cover is to keep debris out of the engine. The way it is designed, it will still allow air in.

 

[packratt]

From looking at some pics of the tool my guess is the tool is used to keep from sucking something into the engine.

 

[buddy]

Ahh, I get it, lightbulb came on, youve removed the air cleaner and turbo for access to do the test. I plan on checking while changing to the ATT.

 

[bison]

In case of low compression on 1 or more cyl,you still need to find out if the rings or valves are causing it.After the first reading,I allways squirt some oil in the GP hole(or injector bore if diff make engine),then crank the engine over to expell the excess(to prevent hydralock) and distribute the rest,then take a second reading.
If no improvement in compression, then the valves are leaking.

 

[gmctd]

Unfortunately, oil is the fuel of choice for this engine - adding oil for the compression test can result in that cylinder, and any others having been squirted, firing as normal - primary reason for the cautionary do not add oil during compression checking blurb on line 7

For the cover in question, a piece of screen door screen works well - I also use an old - very old - chrome Kraco speaker grille

After the main compression test, as outlined above, continue with the leak-down test: pump up the cylinder, stop, bump the starter to get the cylinder near the top of the compression stroke, stop - leave the comp guage connected, observe any needle movement indicating falling pressure due to valves or rings leaking - leakdown rate should be similar, all cylinders should match within 25psi at end of test

 

[chickenhunterbob]

Ahh, I get it, lightbulb came on, youve removed the air cleaner and turbo for access to do the test. I plan on checking while changing to the ATT.

No, but you could. You posted the procedure for any 6.5, but specifically a 6.2 or 6.5 N/A with mech injection.

"Remove air cleaner...disconnect the pink wire..." doesn't have too much relevance to compression test on a >94 6.5 turbodiesel, from #3 on is the same though...