Harbor fright compression gauge

Ok, so the proper fitting will not go in glowplug hole, I have read where some had to cut it off for it to fit. If I cut mine off it will eliminate the shader valve in the end of it. Will it still read pressure?

Schrader

This is the fitting I've used every single time I've done a compression test, and never had an issue with my harbor freight kit. No filing, no grinding, no cutting, just thread it on.

I. Did use that one on the first cylinder but it seem awful short

A have a video on YouTube how to compression test an IDI with a $29 harbor freight tester plus showing where to grind it down to. It will still show accurate pressure. If you search YouTube it will pop right up.

Does anyone with well tuned ears, hear anything disturbing from this engine?

I guess my video didn't attach

Ole BlackBetty said:

Ok, so the proper fitting will not go in glowplug hole, I have read where some had to cut it off for it to fit. If I cut mine off it will eliminate the shader valve in the end of it. Will it still read pressure?

Click to expand...

Here is a good video showing how to use the HF Compression kit, and how to modify the fitting for the GP Hole.



Goat

I don't have a Harbor freight compression tester, I have a KD, so I've not personally dealt with this adapter problem. That said, if you look at the end of the adapter, not the quick-connect end, the other end, you'll see it has a tapered seat, like a brake bleed screw. That's what seals your compression in, so no compression actually gets to the threads. That's important for the glow plugs while the engine is running, you don't want combustion pressure/heat going to the glow plug threads, but when you're just testing compression with an adapter it's not so important.

So if you want to cut the adapter down or use a short adapter like Nero has pictured, that will work. The compression will just be sealed in by the threads rather than a tapered seat.

If you use a cut down or short adapter that doesn't have a valve inside of it that will effect the absolute pressure reading somewhat but will still give you a good indicator of the relative pressure difference from one cylinder to another. This is because without a valve in the adapter the motor has to re-compress the air inside both the gauge hose and the combustion chamber every compression stroke, but with a valve in the the adapter the motor only has to re-compress the combustion chamber every compression stroke and the pressure is retained in the gauge hose and not vented out making for a more accurate test.

So if you can figure out a way to retain the valve in the adapter that will give you a more accurate test but without the valve the test will still be able to show you the relative pressure difference between the cylinders and still be fairly accurate.